HUMAN GENOME SCIENCES INC
8-K, 1999-06-28
IN VITRO & IN VIVO DIAGNOSTIC SUBSTANCES
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<PAGE>   1


                      SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, DC 20549

                           -----------------------

                                   FORM 8-K

                                CURRENT REPORT
                    PURSUANT TO SECTION 13 OR 15(d) OF THE
                       SECURITIES EXCHANGE ACT OF 1934


                                JUNE 25, 1999

                                Date of Report
                      (Date of earliest event reported)



                         HUMAN GENOME SCIENCES, INC.
                         ---------------------------

              (Exact Name of Registrant as Specified in Charter)



         DELAWARE                  0-022962                 22-3178468
         --------                  --------                 ----------
     (State or Other         (Commission File Number)      (IRS Employer
     Jurisdiction of                                     Identification No.)
      Incorporation)





              9410 KEY WEST AVENUE, ROCKVILLE, MARYLAND 20850-3338
              ----------------------------------------------------
              (Address of Principal Executive Offices)   (ZIP Code)




      Registrant's telephone number, including area code: (301) 309-8504



          (Former Name or Former Address, if Changed Since Last Report)



<PAGE>   2



ITEM 5.  OTHER EVENTS.

         On June 25, 1999, Human Genome Sciences, Inc. (the "Company")
completed the sale of its private offering of $100,000,000 aggregate
principal amount of 5-1/2% Convertible Subordinated Notes due 2006 (the
"Notes").  The Company will pay interest on the Notes on July 1 and January 1
of each year, commencing on January 1, 2000.  The Notes will mature on July
1, 2006.

         The Notes are convertible at any time prior to maturity into shares
of the Company's common stock, par value $0.01 per share, at a conversion
price of $52.20 per share, which is equivalent to a conversion rate of
19.1571 shares per $1,000 principal amount of Notes and is subject to
adjustment under the terms of the Notes. The Notes are subordinated to all
of the Company's existing and future senior indebtedness.

         The Company may redeem the Notes on or after July 6, 2002.  Holders
may require the Company to repurchase the Notes upon a Change in Control,
except that this repurchase right does not apply to transactions in which at
least 90% of the consideration consists of common stock and in certain other
circumstances under the terms of the Notes.

         The Company has agreed to file a shelf registration statement
pursuant to a Registration Rights Agreement dated as of June 25, 1999.  In
the event the Company fails to comply with its obligations under the
Registration Rights Agreement, it will pay additional interest on the Notes.


ITEM 7.  FINANCIAL STATEMENTS, PRO FORMA FINANCIAL INFORMATION AND EXHIBITS.

         (c)      Exhibits.

            4.1   Indenture dated as of June 25, 1999 between Human
                  Genome Sciences, Inc. and The Bank of New York, as
                  trustee, including the form of 5-1/2% Convertible
                  Subordinated Notes due 2006 included in Article II
                  thereof.

            4.2   Registration Rights Agreement dated as of June 25,
                  1999 between Human Genome Sciences, Inc. and the
                  Initial Purchaser.




<PAGE>   3



                                  SIGNATURES

            Pursuant to the requirements of the Securities Exchange Act of
1934, the Registrant has duly caused this report to be signed on its behalf
by the undersigned hereunto duly authorized.

                                        HUMAN GENOME SCIENCES, INC.



Date:  June 28, 1999                    By:  /s/ Steven C. Mayer
                                             -------------------------------
                                             Steven C. Mayer
                                             Senior Vice President and Chief
                                              Financial Officer




<PAGE>   4



<TABLE>
<CAPTION>
                                  EXHIBIT INDEX


Exhibit Number    Description
- --------------    -----------
<S>               <C>
   4.1            Indenture dated as of June 25, 1999 between Human
                  Genome Sciences, Inc. and The Bank of New York, as
                  trustee, including the form of 5-1/2% Convertible
                  Subordinated Notes due 2006 included in Article II
                  thereof.

   4.2            Registration Rights Agreement dated as of June 25,
                  1999 between Human Genome Sciences, Inc. and the
                  Initial Purchaser.
</TABLE>




<PAGE>   1
                                                                  EXECUTION COPY

EXHIBIT 4.1
- -----------

================================================================================




                                    INDENTURE

                           HUMAN GENOME SCIENCES, INC.

                                       to

                              THE BANK OF NEW YORK

                                     Trustee



                 5-1/2% Convertible Subordinated Notes Due 2006


                            Dated as of June 25, 1999




================================================================================
<PAGE>   2


<TABLE>
<CAPTION>
                                                                                    Page
                                                                                    ----

                                Table of Contents
                                -----------------
                                                                                    Page
                                                                                    ----
                                    ARTICLE I

             Definitions and Other Provisions of General Application
             -------------------------------------------------------
<S>                                                                                  <C>
SECTION 1.01.    Definitions......................................................... 1
SECTION 1.02.    Compliance Certificates and Opinions................................ 9
SECTION 1.03.    Form of Documents Delivered to Trustee.............................. 9
SECTION 1.04.    Acts of Holders: Record Dates ..................................... 10
SECTION 1.05.    Notices, etc., to Trustee and Company.............................. 12
SECTION 1.06.    Notice to Holders: Waiver.......................................... 12
SECTION 1.07.    Conflict with Trust Indenture Act.................................. 12
SECTION 1.08.    Effect of Headings and Table of Contents........................... 13
SECTION 1.09.    Successors and Assigns............................................. 13
SECTION 1.10.    Severability Clause................................................ 13
SECTION 1.11.    Benefits of Indenture.............................................. 13
SECTION 1.12.    Governing Law...................................................... 13
SECTION 1.13.    Legal Holidays..................................................... 13

                                   ARTICLE II

                                 Security Forms
                                 --------------

SECTION 2.01.    Forms Generally.................................................... 13
SECTION 2.02.    Form of Face of Security........................................... 14
SECTION 2.03.    Form of Reverse of Security ....................................... 18
SECTION 2.04.    Form of Trustee's Certificate of Authentication.................... 22
SECTION 2.05.    Form of Conversion Notice.......................................... 22
SECTION 2.06.    Form of Certification.............................................. 23

                                   ARTICLE III

                                 The Securities
                                 --------------

SECTION 3.01.    Title and Terms.................................................... 24
SECTION 3.02.    Denominations...................................................... 25
SECTION 3.03.    Execution, Authentication, Delivery and Dating..................... 25
SECTION 3.04.    Global and Non-Global Securities................................... 26
SECTION 3.05.    Registration; Registration of Transfer and Exchange................ 27
SECTION 3.06.    Mutilated, Destroyed, Lost and Stolen Securities................... 30
SECTION 3.07.    Payment of Interest; Interest Rights Preserved .................... 31
SECTION 3.08.    Persons Deemed Owners.............................................. 32
SECTION 3.09.    Cancellation....................................................... 33
SECTION 3.10.    Computation of Interest............................................ 33
</TABLE>


                                      -ii-
<PAGE>   3

<TABLE>
<CAPTION>
                                                                                     Page
                                                                                     ----
                                   ARTICLE IV

                           Satisfaction and Discharge
                           --------------------------
<S>                                                                                   <C>
SECTION 4.01.    Satisfaction and Discharge of Indenture............................. 33
SECTION 4.02.    Application of Trust Money.......................................... 34

                                    ARTICLE V

                                    Remedies
                                    --------

SECTION 5.01.    Events of Default................................................... 34
SECTION 5.02.    Acceleration of Maturity; Rescission and Annulment.................. 36
SECTION 5.03.    Collection of Indebtedness and Suits for Enforcement
                   by Trustee........................................................ 37
SECTION 5.04.    Trustee May File Proofs of Claim.................................... 37
SECTION 5.05.    Trustee May Enforce Claims Without Possession of
                   Securities........................................................ 38
SECTION 5.06.    Application of Money Collected...................................... 38
SECTION 5.07.    Limitation on Suits................................................. 39
SECTION 5.08.    Unconditional Right of Holders to Receive Principal,
                   Premium and Interest and To Convert............................... 39
SECTION 5.09.    Restoration of Rights and Remedies.................................. 40
SECTION 5.10.    Rights and Remedies Cumulative...................................... 40
SECTION 5.11.    Delay or Omission Not Waiver........................................ 40
SECTION 5.12.    Control by Holders.................................................. 40
SECTION 5.13.    Waiver of Past Defaults............................................. 40
SECTION 5.14.    Undertaking for Costs............................................... 41
SECTION 5.15.    Waiver of Usury, Stay or Extension Laws............................. 41

                                   ARTICLE VI

                                   The Trustee
                                   -----------

SECTION 6.01.    Certain Duties and Responsibilities................................. 41
SECTION 6.02.    Notice of Defaults.................................................. 42
SECTION 6.03.    Certain Rights of Trustee........................................... 42
SECTION 6.04.    Not Responsible for Recitals or Issuance of Securities.............. 43
SECTION 6.05.    May Hold Securities................................................. 43
SECTION 6.06.    Money Held in Trust................................................. 44
SECTION 6.07.    Compensation and Reimbursement...................................... 44
SECTION 6.08.    Disqualification; Conflicting Interests............................. 44
SECTION 6.09.    Corporate Trustee Required; Eligibility............................. 44
SECTION 6.10.    Resignation and Removal; Appointment of Successor................... 45
SECTION 6.11.    Acceptance of Appointment by Successor.............................. 46
SECTION 6.12.    Merger, Conversion, Consolidation or Succession
                   to Business ...................................................... 46
SECTION 6.13.    Preferential Collection of Claims Against Company .................. 46
SECTION 6.14.    Appointment of Authenticating Agent................................. 47
</TABLE>


                                     -iii-
<PAGE>   4

<TABLE>
<CAPTION>
                                                                                     Page
                                                                                     ----
<S>                                                                                   <C>
SECTION 6.15.    Appointment of Co-Trustee........................................... 48

                                   ARTICLE VII

                Holders' Lists and Reports by Trustee and Company
                -------------------------------------------------

SECTION 7.01.    Company to Furnish Trustee Names and Addresses
                   of Holders ....................................................... 48
SECTION 7.02.    Preservation of Information; Communications to
                   Holders........................................................... 49
SECTION 7.03.    Reports by Trustee ................................................. 49
SECTION 7.04.    Reports by Company.................................................. 49

                                  ARTICLE VIII

              Consolidation, Merger, Conveyance, Transfer or Lease
              ----------------------------------------------------

SECTION 8.01.    Company May Consolidate, etc., Only on Certain Terms................ 50
SECTION 8.02.    Successor Substituted............................................... 51

                                   ARTICLE IX

                             Supplemental Indentures
                             -----------------------

SECTION 9.01.    Supplemental Indentures Without Consent of Holders.................. 51
SECTION 9.02.    Supplemental Indentures with Consent of Holders..................... 52
SECTION 9.03.    Execution of Supplemental Indentures................................ 53
SECTION 9.04.    Effect of Supplemental Indentures................................... 53
SECTION 9.05.    Conformity with Trust Indenture Act................................. 53
SECTION 9.06.    Reference in Securities to Supplemental Indentures.................. 53

                                    ARTICLE X

                                    Covenants
                                    ---------

SECTION 10.01.   Payment of Principal, Premium and Interest.......................... 53
SECTION 10.02.   Maintenance of Office or Agency..................................... 53
SECTION 10.03.   Money for Security Payments To Be Held in Trust..................... 54
SECTION 10.04.   Statement by Officers as to Default................................. 55
SECTION 10.05.   Existence........................................................... 55
SECTION 10.06.   Maintenance of Properties........................................... 55
SECTION 10.07.   Payment of Taxes and Other Claims................................... 56
SECTION 10.08.   Waiver of Certain Covenants......................................... 56
SECTION 10.09.   Delivery of Certain Information..................................... 56
SECTION 10.10.   Resale of Certain Securities; Reporting Issuer...................... 56
SECTION 10.11.   Registration Rights................................................. 56
</TABLE>


                                      -iv-
<PAGE>   5

<TABLE>
<CAPTION>
                                                                                     Page
                                                                                     ----
                                   ARTICLE XI

                            Redemption of Securities
                            ------------------------
<S>                                                                                   <C>
SECTION 11.01.   Right of Redemption................................................. 58
SECTION 11.02.   Applicability of Article............................................ 58
SECTION 11.03.   Election to Redeem; Notice to Trustee............................... 58
SECTION 11.04.   Selection by Trustee of Securities to Be Redeemed................... 58
SECTION 11.05.   Notice of Redemption................................................ 59
SECTION 11.06.   Deposit of Redemption Price......................................... 59
SECTION 11.07.   Securities Payable on Redemption Date............................... 59
SECTION 11.08.   Securities Redeemed in Part......................................... 60
SECTION 11.09    Conversion Arrangement on Call for Redemption....................... 60

                                   ARTICLE XII

                           Subordination of Securities
                           ---------------------------

SECTION 12.01.   Securities Subordinate to Senior Indebtedness....................... 61
SECTION 12.02.   Payment over of Proceeds upon Dissolution, Etc...................... 61
SECTION 12.03.   No Payment When Senior Indebtedness in Default...................... 62
SECTION 12.04.   Payment Permitted If No Default..................................... 62
SECTION 12.05.   Subrogation to Rights of Holders of Senior Indebtedness............. 63
SECTION 12.06.   Provisions Solely to Define Relative Rights ........................ 63
SECTION 12.07.   Trustee to Effectuate Subordination................................. 63
SECTION 12.08.   No Waiver of Subordination Provisions............................... 64
SECTION 12.09.   Notice to Trustee................................................... 64
SECTION 12.10.   Reliance on Judicial Order or Certificate of
                   Liquidating Agent................................................. 65
SECTION 12.11.   Trustee Not Fiduciary for Holders of Senior Indebtedness............ 65
SECTION 12.12.   Rights of Trustee as Holder of Senior Indebtedness;
                   Preservation of Trustee's Rights.................................. 65
SECTION 12.13.   Article Applicable to Paying Agents................................. 65
SECTION 12.14.   Certain Conversions Deemed Payment.................................. 66

                                  ARTICLE XIII

                            Conversion of Securities
                            ------------------------

SECTION 13.01.   Conversion Privilege and Conversion Price........................... 66
SECTION 13.02.   Exercise of Conversion Privilege.................................... 67
SECTION 13.03.   Fractions of Shares................................................. 68
SECTION 13.04.   Adjustment of Conversion Price...................................... 68
SECTION 13.05.   Notice of Adjustments of Conversion Price........................... 73
SECTION 13.06.   Notice of Certain Corporate Action.................................. 73
SECTION 13.07.   Company to Reserve Common Stock..................................... 74
SECTION 13.08.   Taxes on Conversions................................................ 74
SECTION 13.09.   Covenant as to Common Stock......................................... 75
</TABLE>


                                      -v-
<PAGE>   6

<TABLE>
<CAPTION>
                                                                                     Page
                                                                                     ----
<S>                                                                                   <C>
SECTION 13.10.   Cancellation of Converted Securities................................ 75
SECTION 13.11.   Provisions in Case of Reclassification, Consolidation,
                   Merger or Sale of Assets.......................................... 75

                                   ARTICLE XIV

                           Right to Require Repurchase
                           ---------------------------

SECTION 14.01.   Right to Require Repurchase......................................... 75
SECTION 14.02.   Notice, Method of Exercising Repurchase Right ...................... 76
SECTION 14.03.   Deposit of Repurchase Price......................................... 76
SECTION 14.04.   Securities Not Repurchased on Repurchase Date....................... 77
SECTION 14.05.   Securities Repurchased in Part...................................... 77
SECTION 14.06.   Certain Definitions................................................. 77

                                   ARTICLE XV

                       Defeasance and Covenant Defeasance
                       ----------------------------------

SECTION 15.01.   Company's Option to Effect Defeasance or Covenant
                   Defeasance........................................................ 78
SECTION 15.02.   Defeasance and Discharge............................................ 78
SECTION 15.03.   Covenant Defeasance................................................. 79
SECTION 15.04.   Conditions to Defeasance or Covenant Defeasance..................... 79
SECTION 15.05.   Deposited Money and U.S. Government Obligations
                   to Be Held in Trust; Other Miscellaneous Provisions............... 81
SECTION 15.06.   Reinstatement....................................................... 81

                                   ARTICLE XVI

                                    Immunity
                                    --------

SECTION 16.01.   Personal Immunity of Incorporators, Shareholders,
                   Directors and Officers ........................................... 82
</TABLE>


                                      -vi-

<PAGE>   7

                                          INDENTURE dated as of June 25, 1999,
                            between HUMAN GENOME SCIENCES, INC., a corporation
                            duly organized and existing under the laws of the
                            State of Delaware (herein called the "Company"),
                            having its principal office at 9410 Key West Avenue,
                            Rockville, Maryland 20850-3338, and THE BANK OF NEW
                            YORK, as Trustee (herein called the "Trustee").

              The Company has duly authorized the execution and delivery of this
Indenture to provide for the issuance of its 5-1/2% Convertible Subordinated
Notes due 2006 (herein called the "Securities"), to be issued as in this
Indenture provided.

              All things necessary to make the Securities, when executed by the
Company and authenticated and delivered hereunder and duly issued by the
Company, the valid obligations of the Company, and to make this Indenture a
valid agreement of the Company, in accordance with their and its terms, have
been done.


                             W I T N E S S E T H :

              For and in consideration of the premises and the purchase of the
Securities by the Holders thereof, it is mutually agreed, for the equal and
proportionate benefit of all Holders of the Securities or of any series thereof,
as follows:

                                    ARTICLE I

             Definitions and Other Provisions of General Application

              SECTION 1.01. Definitions. For all purposes of this Indenture,
except as otherwise expressly provided or unless the context otherwise requires:

              1. The terms defined in this Article have the meanings assigned to
them in this Article and include the plural as well as the singular.

              2. All other terms used herein which are defined in the Trust
Indenture Act, either directly or by reference therein, have the meanings
assigned to them therein.

              3. All accounting terms not otherwise defined herein have the
meanings assigned to them in accordance with generally accepted accounting
principles, and, except as otherwise herein expressly provided, the term
"generally accepted accounting principles" with respect to any computation
required or permitted hereunder shall mean such accounting principles as are
generally accepted at the date of such computation.

              4. Unless the context otherwise requires, any reference to an
"Article" or a "Section" refers to an Article or Section, as the case may be, of
this Indenture.

              5. The words "herein", "hereof and "hereunder" and other words of
similar import refer to this Indenture as a whole and not to any particular
Article, Section or other subdivision.


<PAGE>   8
                                                                               2


              Certain terms used in Article XIV have the meanings specified
therein.

              "Act", when used with respect to any Holder, has the meaning
specified in Section 1.04.

              "Additional Interest" has the meaning specified in Section 10.11.

              "Affiliate" of any specified Person means any other Person who
directly, or indirectly through one or more intermediaries, controls, is
controlled by, or is under common control with, such specified Person. For the
purposes of this definition, "control" when used with respect to any specified
Person means the power to direct the management and policies of such Person,
directly or indirectly, whether through the ownership of voting securities, by
contract or otherwise; and the terms "controlling" and "controlled" have
meanings correlative to the foregoing.

              "Agent Member" means any member of, or participant in, the
Depositary.

              "Applicable Procedures" means, with respect to any transfer or
transaction involving a Global Security or beneficial interest therein, the
rules and procedures of the Depositary for such Security, in each case to the
extent applicable to such transaction and as in effect from time to time.

              "Authenticating Agent" means any Person authorized by the Trustee
pursuant to Section 6.14 to act on behalf of the Trustee to authenticate
Securities.

              "Beneficial Owner" has the meaning specified in Section 14.06.

              "Board of Directors" means either the board of directors of the
Company or any duly authorized committee of that board.

              "Board Resolution" means a copy of a resolution certified by the
Secretary or an Assistant Secretary of the Company to have been duly adopted by
the Board of Directors and to be in full force and effect on the date of such
certification, and delivered to the Trustee.

              "Business Day" means a day on which banking institutions are open
for business and carrying out transactions in Dollars at the relevant place of
payment.

              "Change in Control" has the meaning specified in Section 14.06.

              "Closing Price" on any Trading Day with respect to the per share
price of Common Stock means the last reported sales price regular way or, in
case no such reported sale takes place on such Trading Day, the average of the
reported closing bid and asked prices regular way, in either case on the New
York Stock Exchange or, if the Common Stock is not listed or admitted to trading
on the New York Stock Exchange, on the principal national securities exchange on
which the Common Stock is listed or admitted to trading, or, if not listed or
admitted to trading on any national securities exchange, on The Nasdaq Stock
Market, Inc. ("Nasdaq") or, if the Common Stock is not listed or admitted to
trading on any national securities exchange or Nasdaq, the average of the
closing bid and asked prices in the over-the-counter market as furnished by any


<PAGE>   9
                                                                               3


New York Stock Exchange member firm that is selected from time to time by the
Company for that purpose and is reasonably acceptable to the Trustee.

              "Commencement Date" has the meaning specified in Section 13.04.

              "Commission" means the Securities and Exchange Commission, as from
time to time constituted, created under the Exchange Act, or, if at any time
after the execution of this instrument such Commission is not existing and
performing the duties now assigned to it under the Trust Indenture Act, then the
body performing such duties at such time.

              "Common Stock" includes any stock of any class of the Company
which has no preference in respect of dividends or of amounts payable in the
event of any voluntary or involuntary liquidation, dissolution or winding-up of
the Company and which is not subject to redemption by the Company. However,
subject to the provisions of Section 13.11, shares issuable on conversion of
Securities shall include only shares of the class designated as Common Stock of
the Company at the date of this instrument or shares of any class or classes
resulting from any reclassification or reclassifications thereof and which have
no preference in respect of dividends or of amounts payable in the event of any
voluntary or involuntary liquidation, dissolution or winding-up of the Company
and which are not subject to redemption by the Company; provided that if at any
time there shall be more than one such resulting class, the shares of each such
class then so issuable shall be substantially in the proportion which the total
number of shares of such class resulting from all such reclassifications bears
to the total number of shares of all such classes resulting from all such
reclassifications.

              "Company" means the Person named as the "Company" in the first
paragraph of this instrument until a successor Person shall have become such
pursuant to the applicable provisions of this Indenture, and thereafter
"Company" shall mean such successor Person.

              "Company Order" has the meaning specified in the definition of
Company Request in this Section 1.01.

              "Company Request" or "Company Order" means a written request or
order signed in the name of the Company by its Chairman of the Board, its Vice
Chairman of the Board, its President or a Vice President, and by its Treasurer,
an Assistant Treasurer, its Secretary or an Assistant Secretary, and delivered
to the Trustee.

              "Corporate Trust Office" means the principal office of the Trustee
in the city at which at any particular time its corporate trust business shall
be administered. As of the date hereof, the Corporate Trust Office of the
Trustee is located at 101 Barclay Street, Floor 21 West, New York, New York
10286.

              "Corporation" means a corporation, association, company,
joint-stock company or business trust.

              "Current Event" has the meaning specified in Section 13.04.

              "Defaulted Interest" has the meaning specified in Section 3.07.


<PAGE>   10
                                                                               4


              "Depositary" means, with respect to the Securities issued in whole
or in part in the form of one or more Global Securities, a clearing agency
registered under the Exchange Act that is designated to act as Depositary for
such Securities as contemplated by Section 2.01 (or any successor securities
clearing agency so registered).

              "Distribution Date" has the meaning specified in Section 13.04.

              "Dollar" or "U.S.$" means a Dollar or other equivalent unit in
such coin or currency of the United States as at the time shall be legal tender
for the payment of public and private debts.

              "DTC" means The Depository Trust Company, a New York corporation.

              "Event of Default" has the meaning specified in Section 5.01.

              "ex date" has the meaning specified in Section 13.04.

              "Exchange Act" means the Securities Exchange Act of 1934 as it may
be amended from time to time, and any successor act thereto, and the rules and
regulations of the Commission promulgated thereunder.

              "Expiration Date" has the meaning specified in Section 1.04.

              "Expiration Time" has the meaning specified in Section 13.04.

              "Global Security" means a Security that is registered in the
Security Register in the name of a Depositary or a nominee thereof.

              "Group" has the meaning specified in Section 14.06.

              "Holder" means a Person in whose name a Security is registered in
the Security Register.

              "Indenture" means this instrument as originally executed or as it
may from time to time be supplemented or amended by one or more indentures
supplemental hereto entered into pursuant to the applicable provisions hereof,
including, for all purposes of this instrument and any such supplemental
indenture, the provisions of the Trust Indenture Act that are deemed to be a
part of and govern this instrument and any such supplemental indenture,
respectively.

              "Initial Purchasers" means Credit Suisse First Boston Corporation
and Merrill Lynch, Pierce, Fenner & Smith Incorporated.

              "Interest Payment Date" means the Stated Maturity of an
installment of interest on the Securities.

              "Issue Date" means the date of first issuance of the Securities
under this Indenture.

              "junior securities" has the meaning specified in Section 12.14.


<PAGE>   11
                                                                               5


              "Maturity", when used with respect to any Security, means the date
on which the principal of such Security or an installment of principal becomes
due and payable as therein or herein provided, whether at the Stated Maturity or
by declaration of acceleration, call for redemption, exercise of the repurchase
right or otherwise.

              "Nasdaq" has the meaning specified in the definition of Closing
Price in this Section 1.01.

              "Non-Recourse Obligation" means indebtedness or other obligation
or that portion of indebtedness or other obligation incurred by a Subsidiary
(the "Non-Recourse Subsidiary") with respect to the acquisition of assets not
previously owned by the Company or any Subsidiary or the financing of a project
involving the development or expansion of properties of the Company or any
Subsidiary (i) as to which neither the Company nor any of its Subsidiaries
(other than the Non-Recourse Subsidiary) (a) provides credit support (including
any undertaking, agreement or instrument that would constitute indebtedness),
(b) is directly or indirectly liable (as a guarantor or otherwise), or (c)
constitutes the lender; and (ii) no default with respect to which would permit
(upon notice, lapse of time or both) any holder of any other indebtedness of the
Company or any of its Subsidiaries to declare a default under such other
indebtedness or cause the payment thereof to be accelerated or payable prior to
its stated maturity; and (iii) as to which the lenders have been notified in
writing that they will not have any recourse to the stock or assets of the
Company or any Subsidiary other than the assets that were acquired with the
proceeds of such transaction or the project financed with the proceeds of such
transaction (and the proceeds thereof).

              "Non-Recourse Subsidiary" has the meaning specified in the
definition of Non-Recourse Obligation in this Section 1.01.

              "Notice of Default" means a written notice of the kind specified
in Section 5.01(4) or 5.01(5).

              "Officers' Certificate" means a certificate signed by any of the
Chairman of the Board, a Vice Chairman of the Board, the President or a Vice
President, and by any of the Treasurer, an Assistant Treasurer, the Secretary or
an Assistant Secretary, of the Company, and delivered to the Trustee. One of the
officers signing an Officers' Certificate given pursuant to Section 10.04 shall
be the principal executive, financial or accounting officer of the Company.

              "Opinion of Counsel" means a written opinion of counsel, who may
be counsel for the Company.

              "Other Event" has the meaning specified in Section 13.04.

              "Outstanding", when used with respect to Securities, means, as of
the date of determination, all Securities theretofore authenticated and
delivered under this Indenture, except:

              (i) Securities theretofore cancelled by the Trustee or delivered
       to the Trustee for cancellation;


<PAGE>   12
                                                                               6


              (ii) Securities for whose payment or redemption money in the
       necessary amount has been theretofore deposited with the Trustee or any
       Paying Agent (other than the Company) in trust or set aside and separated
       in trust by the Company (if the Company shall act as its own Paying
       Agent) for the Holders of such Securities; provided that, if such
       Securities are to be redeemed, notice of such redemption shall have been
       duly given pursuant to this Indenture or provision therefor satisfactory
       to the Trustee shall have been made;

              (iii) Securities which have been paid pursuant to Section 3.07 or
       in exchange for or in lieu of which other Securities have been
       authenticated and delivered pursuant to this Indenture, other than any
       such Securities in respect of which there shall have been presented to
       the Trustee proof satisfactory to it that such Securities are held by a
       bona fide purchaser in whose hands such Securities are valid obligations
       of the Company; and

              (iv) Securities which have been defeased pursuant to Section
       15.02;


provided, however, that in determining whether the Holders of the requisite
principal amount of the Outstanding Securities have given, made or taken any
request, demand, authorization, direction, notice, consent, waiver or other
action hereunder as of any date, Securities owned by the Company or any other
obligor upon the Securities or any Affiliate of the Company or of such other
obligor shall be disregarded and deemed not to be Outstanding, except that, in
determining whether the Trustee shall be protected in relying upon any such
request, demand, authorization, direction, notice, consent, waiver or other
action, only Securities which a Responsible Officer of the Trustee knows to be
so owned shall be so disregarded. Securities so owned which have been pledged in
good faith may be regarded as Outstanding if the pledgee establishes to the
satisfaction of the Trustee the pledgee's right so to act with respect to such
Securities and that the pledgee is not the Company or any other obligor upon the
Securities or any Affiliate of the Company or of such other obligor.

              "Paying Agent" means any Person authorized by the Company to pay
the principal of (and premium, if any) or interest on any Securities on behalf
of the Company.

              "Person" means any individual, corporation, partnership, joint
venture, trust, unincorporated organization or government or any agency or
political subdivision thereof.

              "Predecessor Security" of any particular Security means every
previous Security evidencing all or a portion of the same debt as that evidenced
by such particular Security; and, for the purposes of this definition, any
Security authenticated and delivered under Section 3.06 in exchange for or in
lieu of a mutilated, destroyed, lost or stolen Security shall be deemed to
evidence the same debt as the mutilated, destroyed, lost or stolen Security.

              "Purchased Shares" has the meaning specified in Section 13.04.

              "Qualified Institutional Buyer" means a "qualified institutional
buyer" as defined in Rule 144A.


<PAGE>   13
                                                                               7


              "Redemption Date", when used with respect to any Security to be
redeemed, means the date fixed for such redemption by or pursuant to this
Indenture.

              "Redemption Price", when used with respect to any Security to be
redeemed, means the price at which it is to be redeemed as set forth in the
Securities.

              "Reference Date" has the meaning specified in Section 13.04.

              "Registration Default" has the meaning specified in Section 10.11.

              "Registration Rights Agreement" has the meaning specified in
Section 10.11.

              "Regular Record Date" for the interest payable on any Interest
Payment Date means the June 15 or December 15 (whether or not a Business Day),
as the case may be, next preceding such Interest Payment Date.

              "Repurchase Date" has the meaning specified in Section 14.01.

              "Repurchase Price" has the meaning specified in Section 14.01.

              "Responsible Officer", when used with respect to the Trustee,
means any officer in the corporate trust department of the Trustee to whom any
matter has been referred because of such officer's knowledge and familiarity
with the particular subject.

              "Restricted Global Security" has the meaning specified in Section
2.01.

              "Restricted Security" means a Security required to bear the
restricted securities legend set forth in Section 2.02.

              "Rule 144A" means Rule 144A under the Securities Act (or any
successor provision), as it may be amended from time to time.

              "Rule 144A Information" has the meaning specified in Section
10.09.

              "Securities" has the meaning stated in the first recital of this
Indenture and more particularly means any Securities authenticated and delivered
under this Indenture and "Security" means one of such Securities.

              "Securities Act" means the Securities Act of 1933 as it may be
amended from time to time, and any successor act thereto, and the rules and
regulations of the Commission promulgated thereunder.

              "Security Register" has the meaning specified in Section 3.05.

              "Security Registration" has the meaning specified in Section 3.05.

              "Senior Indebtedness" means the principal of and premium, if any,
and interest on all indebtedness of the Company for money borrowed, other than
the Securities, whether outstanding on the date of execution of the Indenture or
thereafter created, incurred, guaranteed or assumed, except such indebtedness
that by the terms of


<PAGE>   14
                                                                               8


the instrument or instruments by which such indebtedness was created or incurred
expressly provides that it (i) is junior in right of payment to the Securities
or any other indebtedness of the Company for borrowed money or (ii) ranks pari
passu in right of payment to the Securities. The term "indebtedness for money
borrowed" when used with respect to the Company is defined to mean (i) any
obligation of, or any obligation guaranteed by, the Company for the repayment of
borrowed money, whether or not evidenced by bonds, debentures, notes or other
written instruments, (ii) all obligations of the Company with respect to
interest rate hedging agreements to hedge interest rates relating to Senior
Indebtedness of the Company, (iii) any deferred payment obligation of, or any
such obligation guaranteed by, the Company for the payment of the purchase price
of property or assets evidenced by a note or similar instrument, and (iv) any
obligation of, or any such obligation guaranteed by, the Company for the payment
of rent or other amounts under a lease of property or assets which obligation is
required to be classified and accounted for as a capitalized lease on the
balance sheet of the Company under generally accepted accounting principles.

              "Shelf Registration Statement" has the meaning specified in
Section 10.11.

              "Special Record Date" for the payment of any Defaulted Interest
means a date fixed by the Trustee pursuant to Section 3.07.

              "Stated Maturity", when used with respect to any Security or any
installment of principal thereof or interest thereon, means the date specified
in such Security as the fixed date on which the principal of such Security or
such installment of principal or interest is due and payable.

              "Subsidiary" means a corporation more than 50% of the outstanding
voting stock of which is owned, directly or indirectly, by the Company or by one
or more other Subsidiaries, or by the Company and one or more other
Subsidiaries. For the purposes of this definition, "voting stock" means stock
which ordinarily has voting power for the election of directors, whether at all
times or only so long as no senior class of stock has such voting power by
reason of any contingency.

              "Surrendered Securities" has the meaning specified in Section
2.06.

              "Trading Day" means each Monday, Tuesday, Wednesday, Thursday and
Friday, other than any day on which securities are not traded on the applicable
securities exchange or in the applicable securities market.

              "Transfer Restricted Securities" has the meaning specified in the
Registration Rights Agreement.

              "Trust Indenture Act" means the Trust Indenture Act of 1939 as in
force at the date as of which this instrument was executed and the rules and
regulations thereunder; provided, however, that in the event the Trust Indenture
Act of 1939 or such rules and regulations are amended after such date, "Trust
Indenture Act" means, to the extent required by any such amendment, the Trust
Indenture Act of 1939 and such rules and regulations as so amended.


<PAGE>   15
                                                                               9


              "Trustee" means the Person named as the "Trustee" in the first
paragraph of this instrument until a successor Trustee shall have become such
pursuant to the applicable provisions of this Indenture, and thereafter
"Trustee" shall mean such successor Trustee.

              "United States" means the United States of America (including the
States thereof and the District of Columbia), its territories, its possessions
and other areas subject to its jurisdiction.

              "U.S. Government Obligation" has the meaning specified in Section
15.04.

              "Vice President", when used with respect to the Company or the
Trustee, means any vice president, whether or not designated by a number or a
word or words added before or after the title "vice president".

              SECTION 1.02. Compliance Certificates and Opinions. Upon any
application or request by the Company to the Trustee to take any action under
any provision of this Indenture, the Company shall furnish to the Trustee an
Officers' Certificate, if to be given by an officer of the Company, or an
Opinion of Counsel, if to be given by counsel, stating that all conditions
precedent, if any, provided for in this Indenture relating to the proposed
action have been complied with.

              Every certificate or opinion with respect to compliance with a
condition or covenant provided for in this Indenture shall include:

              (a) a statement that each individual signing such certificate or
opinion has read such covenant or condition and the definitions herein relating
thereto;

              (b) a brief statement as to the nature and scope of the
examination or investigation upon which the statements or opinions contained in
such certificate or opinion are based;

              (c) a statement that, in the opinion of each such individual, he
has made such examination or investigation as is necessary to enable him to
express an informed opinion as to whether or not such covenant or condition has
been complied with; and

              (d) a statement as to whether, in the opinion of each such
individual, such condition or covenant has been complied with.

              SECTION 1.03. Form of Documents Delivered to Trustee. In any case
where several matters are required to be certified by, or covered by an opinion
of, any specified Person, it is not necessary that all such matters be certified
by, or covered by the opinion of, only one such Person, or that they be so
certified or covered by only one document, but one such Person may certify or
give an opinion with respect to some matters and one or more other such Persons
as to other matters, and any such Person may certify or give an opinion as to
such matters in one or several documents.

              Any certificate or opinion of an officer of the Company may be
based, insofar as it relates to legal matters, upon a certificate or opinion of,
or representations


<PAGE>   16
                                                                              10


by, counsel, unless such officer knows, or in the exercise of reasonable care
should know, that the certificate or opinion or representations with respect to
the matters upon which his certificate or opinion is based are erroneous. Any
such certificate or Opinion of Counsel may be based, insofar as it relates to
factual matters, upon a certificate or opinion of, or representations by, an
officer or officers of the Company stating that the information with respect to
such factual matters is in the possession of the Company, unless such counsel
knows, or in the exercise of reasonable care should know, that the certificate
or opinion or representations with respect to such matters are erroneous.

              Where any Person is required to make, give or execute two or more
applications, requests, consents, certificates, statements, opinions or other
instruments under this Indenture, they may, but need not, be consolidated and
form one instrument.

              SECTION 1.04. Acts of Holders; Record Dates. Any request, demand,
authorization, direction, notice, consent, waiver or other action provided or
permitted by this Indenture to be given or taken by Holders may be embodied in
and evidenced by one or more instruments of substantially similar tenor signed
by such Holders in person or by an agent duly appointed in writing; and, except
as herein otherwise expressly provided, such action shall become effective when
such instrument or instruments are delivered to the Trustee and, where it is
hereby expressly required, to the Company. Such instrument or instruments (and
the action embodied therein and evidenced thereby) are herein sometimes referred
to as the "Act" of the Holders signing such instrument or instruments. Proof of
execution of any such instrument or of a writing appointing any such agent shall
be sufficient for any purpose of this Indenture and (subject to Section 6.01)
conclusive in favor of the Trustee and the Company, if made in the manner
provided in this Section 1.04.

              The fact and date of the execution by any Person of any such
instrument or writing may be proved by the affidavit of a witness of such
execution or by a certificate of a notary public or other officer authorized by
law to take acknowledgments of deeds, certifying that the individual signing
such instrument or writing acknowledged to him the execution thereof. Where such
execution is by a signer acting in a capacity other than his individual
capacity, such certificate or affidavit shall also constitute sufficient proof
of his authority. The fact and date of the execution of any such instrument or
writing, or the authority of the Person executing the same, may also be proved
in any other manner which the Trustee deems sufficient.

              The ownership of Securities shall be proved by the Security
Register.

              Any request, demand, authorization, direction, notice, consent,
waiver or other Act of the Holder of any Security shall bind every future Holder
of the same Security and the Holder of every Security issued upon the
registration of transfer thereof or in exchange therefor or in lieu thereof in
respect of anything done, omitted or suffered to be done by the Trustee or the
Company in reliance thereon, whether or not notation of such action is made upon
such Security.

              The Company may set any day as a record date for the purpose of
determining the Holders of Outstanding Securities entitled to give or take any
request, demand, authorization, direction, notice, consent, waiver or other
action provided or permitted by this Indenture to be given or taken by Holders
of Securities; provided that the Company may not set a record date for, and the
provisions of this paragraph shall not


<PAGE>   17
                                                                              11


apply with respect to, the giving or making of any notice, declaration, request
or direction referred to in the next paragraph. If any record date is set
pursuant to this paragraph, the Holders of Outstanding Securities on such record
date, and no other Holders, shall be entitled to take the relevant action,
whether or not such Holders remain Holders after such record date; provided that
no such action shall be effective hereunder unless taken on or prior to the
applicable Expiration Date by Holders of the requisite principal amount of
Outstanding Securities on such record date; and provided further, that for the
purpose of determining whether Holders of the requisite principal amount of such
Securities have taken such action, no Security shall be deemed to have been
Outstanding on such record date unless it is also Outstanding on the date such
action is to become effective. Nothing in this paragraph shall prevent the
Company from setting a new record date for any action for which a record date
has previously been set pursuant to this paragraph (whereupon the record date
previously set shall automatically and with no action by any Person be cancelled
and of no effect), nor shall anything in this paragraph be construed to render
ineffective any action taken by Holders of the requisite principal amount of
Outstanding Securities on the date such action is taken. Promptly after any
record date is set pursuant to this paragraph, the Company, at its own expense,
shall cause notice of such record date, the proposed action by Holders and the
applicable Expiration Date to be given to the Trustee in writing and to each
Holder of Securities in the manner set forth in Section 1.06.

              The Trustee may set any day as a record date for the purpose of
determining the Holders of Outstanding Securities entitled to join in the giving
or making of (i) any Notice of Default, (ii) any declaration of acceleration
referred to in Section 5.02, (iii) any request to institute proceedings referred
to in Section 5.07(2), or (iv) any direction referred to in Section 5.12. If any
record date is set pursuant to this paragraph, the Holders of Outstanding
Securities on such record date, and no other Holders, shall be entitled to join
in such notice, declaration, request or direction, whether or not such Holders
remain Holders after such record date; provided that no such action shall be
effective hereunder unless taken on or prior to the applicable Expiration Date
by Holders of the requisite principal amount of Outstanding Securities on such
record date; and provided, further, that for the purpose of determining whether
Holders of the requisite principal amount of such Securities have taken such
action, no Security shall be deemed to have been Outstanding on such record date
unless it is also Outstanding on the date such action is to become effective.
Nothing in this paragraph shall be construed to prevent the Trustee from setting
a new record date for any action (whereupon the record date previously set shall
automatically and without any action by any Person be cancelled and of no
effect), nor shall anything in this paragraph be construed to render ineffective
any action taken by Holders of the requisite principal amount of Outstanding
Securities on the date such action is taken. Promptly after any record date is
set pursuant to this paragraph, the Trustee, at the Company's expense, shall
cause notice of such record date, the proposed action by Holders and the
applicable Expiration Date to be given to the Company in writing and to each
Holder of Securities in the manner set forth in Section 1.06.

              With respect to any record date set pursuant to this Section, the
party hereto that sets such record date may designate any day as the "Expiration
Date" and from time to time may change the Expiration Date to any earlier or
later day; provided that no such change shall be effective unless notice of the
proposed new Expiration Date is given to the other party hereto in writing, and
to each Holder of Securities in the manner set forth in Section 1.06, on or
before the existing Expiration Date.


<PAGE>   18
                                                                              12


Notwithstanding the foregoing, no Expiration Date shall be later than the 180th
day after the applicable record date and, if an Expiration Date is not
designated with respect to any record date set pursuant to this Section, the
party hereto that set such record date shall be deemed to have designated the
180th day after such record date as the Expiration Date with respect thereto.

              Without limiting the foregoing, a Holder entitled hereunder to
take any action hereunder with regard to any particular Security may do so with
regard to all or any part of the principal amount of such Security or by one or
more duly appointed agents, each of which may do so pursuant to such appointment
with regard to all or any part of such principal amount.

              SECTION 1.05. Notices, etc. to Trustee and Company. Any request,
demand, authorization, direction, notice, consent, waiver or Act of Holders or
other document provided or permitted by this Indenture to be made upon, given or
furnished to, or filed with,

              (1) the Trustee by any Holder or by the Company shall be
sufficiently given if made, given, furnished or filed in writing to or with the
Trustee at its Corporate Trust Office, Attention: Corporate Trust
Administration, or at any other address previously furnished in writing to the
Company by the Trustee, or

              (2) the Company by the Trustee or by any Holder shall be
sufficiently given (unless otherwise herein expressly provided) if in writing
and mailed, first-class postage prepaid, to the Company, addressed to it at the
address of its principal office specified in the first paragraph of this
instrument or at any other address previously furnished in writing to the
Trustee by the Company.

              SECTION 1.06. Notice to Holders; Waiver. Where this Indenture
provides for notice to Holders of any event, such notice shall be sufficiently
given (unless otherwise herein expressly provided) if in writing and mailed,
first-class postage prepaid, to each Holder affected by such event, at his
address as it appears in the Security Register, not later than the latest date
(if any), and not earlier than the earliest date (if any), prescribed for the
giving of such notice. In any case where notice to Holders is given by mail,
neither the failure to mail such notice, nor any defect in any notice so mailed,
to any particular Holder shall affect the sufficiency of such notice with
respect to other Holders. Where this Indenture provides for notice in any
manner, such notice may be waived in writing by the Person entitled to receive
such notice, either before or after the event, and such waiver shall be the
equivalent of such notice. Waivers of notice by Holders shall be filed with the
Trustee, but such filing shall not be a condition precedent to the validity of
any action taken in reliance upon such waiver.

              In case by reason of the suspension of regular mail service or by
reason of any other cause it shall be impracticable to give such notice by mail,
then such notification as shall be made with the approval of the Trustee shall
constitute a sufficient notification for every purpose hereunder.

              SECTION 1.07. Conflict with Trust Indenture Act. If any provision
hereof limits, qualifies or conflicts with a provision of the Trust Indenture
Act which is required under such Act to be a part of and govern this Indenture,
the latter provision shall control. If any provision of this Indenture modifies
or excludes any provision of the


<PAGE>   19
                                                                              13


Trust Indenture Act which may be so modified or excluded, the latter provision
shall be deemed to apply to this Indenture as so modified or to be excluded, as
the case may be. To the extent a Security conflicts with a provision in the
Indenture, the Indenture governs.

              SECTION 1.08. Effect of Headings and Table of Contents. The
Article and Section headings herein and the Table of Contents are for
convenience only and shall not affect the construction hereof.

              SECTION 1.09. Successors and Assigns. All covenants and agreements
in this Indenture by the Company shall bind its successors and assigns, whether
so expressed or not.

              SECTION 1.10. Severability Clause. In case any provision in this
Indenture or in the Securities shall be invalid, illegal or unenforceable, the
validity, legality and enforceability of the remaining provisions shall not in
any way be affected or impaired thereby.

              SECTION 1.11. Benefits of Indenture. Nothing in this Indenture or
in the Securities, express or implied, shall give to any Person, other than the
parties hereto and their successors hereunder, the holders of Senior
Indebtedness and the Holders of Securities, any benefit or any legal or
equitable right, remedy or claim under this Indenture.

              SECTION 1.12. Governing Law. THIS INDENTURE AND THE SECURITIES
SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAW OF THE STATE OF
NEW YORK WITHOUT REGARD TO CONFLICT OF LAWS PRINCIPLES.

              SECTION 1.13. Legal Holidays. In any case where any Interest
Payment Date, Redemption Date, Repurchase Date or Stated Maturity of any
Security or the last date on which a Holder has the right to convert his
Securities shall not be a Business Day then (notwithstanding any other provision
of this Indenture or of the Securities) payment of interest or principal (and
premium, if any) or conversion of the Securities need not be made on such date,
but may be made on the next succeeding Business Day with the same force and
effect as if made on the Interest Payment Date, Redemption Date, Repurchase Date
or at the Stated Maturity, or on such last day for conversion; provided that no
interest shall accrue for the period from and after such Interest Payment Date,
Redemption Date, Repurchase Date or Stated Maturity, as the case may be.


                                   ARTICLE II

                                 Security Forms

              SECTION 2.01. Forms Generally. The Securities, the conversion
notice and the Trustee's certificates of authentication shall be in
substantially the forms set forth in this Article, with such appropriate
insertions, omissions, substitutions and other variations as are required or
permitted by this Indenture, and may have such letters, numbers or other marks
of identification and such legends or endorsements placed



<PAGE>   20
                                                                              14


thereon as may be required to comply with the rules of any securities exchange
or Depositary therefor or as may, consistently herewith, be determined by the
officers executing such Securities, as evidenced by their execution of the
Securities.

              The definitive Securities shall be printed, lithographed or
engraved on steel engraved borders or may be produced in any other manner, all
as determined by the officers executing such Securities, as evidenced by their
execution of such Securities.

              In certain cases described elsewhere herein, the legends set forth
in the first four paragraphs of Section 2.02 may be omitted from Securities
issued hereunder.

              Upon their original issuance, Securities offered and sold in
reliance on Rule 144A as provided in the Purchase Agreement, shall be issued in
the form of a single Global Security in definitive, fully registered form
without interest coupons, substantially in the form of Security set forth in
Sections 2.02 and 2.03, with such applicable legends as are provided for in
Section 2.02, except as otherwise permitted herein. Such Global Security shall
be registered in the name of DTC, as Depositary, or its nominee, duly executed
by the Company and authenticated by the Trustee as hereinafter provided, and
deposited with the Trustee, as custodian for DTC, for credit by DTC to the
respective accounts of beneficial owners of the Securities represented thereby
(or such other accounts as they may direct). Such Global Security, together with
its Successor Securities which are Global Securities, are collectively herein
called the "Restricted Global Security".

              Except as provided in this Section 2.01 or Section 3.05, owners of
beneficial interests in Global Securities will not be entitled to receive
physical delivery of certificated Securities. Upon transfer of definitive
Securities to a Qualified Institutional Buyer, such definitive Securities will,
unless the Restricted Global Security has previously been exchanged, be
exchanged for an interest in the Restricted Global Security pursuant to the
provisions of Section 3.05.

              Neither the Company nor the Trustee shall have any responsibility
for any defect in the CUSIP number that appears on any Security, check, advice
of payment or redemption or repurchase notice, and any such document may contain
a statement to the effect that CUSIP numbers have been assigned by an
independent service for convenience of reference and that neither the Company
nor the Trustee shall be liable for any inaccuracy in such numbers.

              SECTION 2.02. Form of Face of Security.

              [INCLUDE IF SECURITY IS A RESTRICTED SECURITY OR A DEFINITIVE
SECURITY OTHER THAN A RESTRICTED GLOBAL SECURITY:

              THIS SECURITY (OR ITS PREDECESSOR) WAS ORIGINALLY ISSUED IN A
TRANSACTION EXEMPT FROM REGISTRATION UNDER THE UNITED STATES SECURITIES ACT OF
1933 (THE "SECURITIES ACT"), AND THIS SECURITY AND THE COMMON STOCK ISSUABLE
UPON THE CONVERSION THEREOF MAY NOT BE OFFERED, SOLD OR OTHERWISE TRANSFERRED IN
THE ABSENCE OF SUCH REGISTRATION OR IN A TRANSACTION EXEMPT FROM, OR NOT SUBJECT
TO, THE SECURITIES ACT. EACH PURCHASER OF THIS SECURITY IS HEREBY NOTIFIED THAT
THE


<PAGE>   21
                                                                              15


SELLER OF THIS SECURITY, AND THE COMMON STOCK ISSUABLE UPON THE CONVERSION
THEREOF, MAY BE RELYING ON THE EXEMPTION FROM THE PROVISIONS OF SECTION 5 OF THE
SECURITIES ACT PROVIDED BY RULE 144A THEREUNDER.

              THE HOLDER OF THIS SECURITY AGREES FOR THE BENEFIT OF THE COMPANY
THAT (A) THIS SECURITY AND THE COMMON STOCK ISSUABLE UPON THE CONVERSION THEREOF
MAY BE OFFERED, RESOLD, PLEDGED OR OTHERWISE TRANSFERRED, ONLY (I) TO A PERSON
WHOM THE SELLER REASONABLY BELIEVES IS A QUALIFIED INSTITUTIONAL BUYER (AS
DEFINED IN RULE 144A UNDER THE SECURITIES ACT) IN A TRANSACTION MEETING THE
REQUIREMENTS OF RULE 144A, (II) PURSUANT TO AN EXEMPTION FROM REGISTRATION UNDER
THE SECURITIES ACT PROVIDED BY RULE 144 THEREUNDER (IF AVAILABLE) OR (III)
PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT, IN
EACH OF CASES (I) THROUGH (III) IN ACCORDANCE WITH ANY APPLICABLE SECURITIES
LAWS OF ANY STATE OF THE UNITED STATES, AND (B) THE HOLDER WILL, AND EACH
SUBSEQUENT HOLDER IS REQUIRED TO, NOTIFY ANY PURCHASER OF THIS SECURITY AND ANY
SHARES OF COMMON STOCK ISSUABLE UPON THE CONVERSION THEREOF OF THE RESALE
RESTRICTIONS REFERRED TO IN (A) ABOVE.]

              [INCLUDE IF SECURITY IS A RESTRICTED GLOBAL SECURITY:

              THE SECURITIES EVIDENCED BY THIS GLOBAL SECURITY (OR ITS
PREDECESSOR) WERE ORIGINALLY ISSUED IN A TRANSACTION EXEMPT FROM REGISTRATION
UNDER THE UNITED STATES SECURITIES ACT OF 1933 (THE "SECURITIES ACT"), AND SUCH
SECURITIES AND THE COMMON STOCK ISSUABLE UPON THE CONVERSION THEREOF MAY NOT BE
OFFERED, SOLD OR OTHERWISE TRANSFERRED IN THE ABSENCE OF SUCH REGISTRATION OR IN
A TRANSACTION EXEMPT FROM, OR NOT SUBJECT TO, THE SECURITIES ACT. EACH PURCHASER
OF ANY BENEFICIAL INTEREST IN THE SECURITIES IS HEREBY NOTIFIED THAT THE SELLER
OF SUCH BENEFICIAL INTEREST MAY BE RELYING ON THE EXEMPTION FROM THE PROVISIONS
OF SECTION 5 OF THE SECURITIES ACT PROVIDED BY RULE 144A THEREUNDER.

              EACH BENEFICIAL OWNER OF AN INTEREST IN ANY OF THE SECURITIES
EVIDENCED BY THIS GLOBAL SECURITY (INCLUDING ANY PARTICIPANT IN THE DEPOSITARY
HOLDING THE GLOBAL SECURITY THAT IS SHOWN AS HOLDING SUCH AN INTEREST ON THE
RECORDS OF SUCH DEPOSITARY AND EACH BENEFICIAL OWNER THAT HOLDS THROUGH SUCH
PARTICIPANT) AGREES FOR THE BENEFIT OF THE COMPANY THAT (A) ANY BENEFICIAL
INTEREST IN THE SECURITIES AND THE COMMON STOCK ISSUABLE UPON THE CONVERSION
THEREOF MAY BE OFFERED, RESOLD, PLEDGED OR OTHERWISE TRANSFERRED, ONLY (I) TO A
PERSON WHOM THE SELLER REASONABLY BELIEVES IS A QUALIFIED INSTITUTIONAL BUYER
(AS DEFINED IN RULE 144A UNDER THE SECURITIES ACT) IN A TRANSACTION MEETING THE
REQUIREMENTS OF RULE 144A, (II) PURSUANT TO AN EXEMPTION FROM REGISTRATION UNDER
THE SECURITIES ACT PROVIDED BY RULE 144 THEREUNDER (IF


<PAGE>   22
                                                                              16


AVAILABLE) OR (III) PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE
SECURITIES ACT, IN EACH OF CASES (I) THROUGH (III) IN ACCORDANCE WITH ANY
APPLICABLE SECURITIES LAWS OF ANY STATE OF THE UNITED STATES, AND (B) THE
BENEFICIAL OWNER WILL, AND EACH SUBSEQUENT BENEFICIAL OWNER OF THIS SECURITY OR
ANY SHARES OF COMMON STOCK ISSUABLE UPON CONVERSION THEREOF IS REQUIRED TO,
NOTIFY ANY PURCHASER OF ANY BENEFICIAL INTEREST IN THE SECURITIES AND ANY SHARES
OF COMMON STOCK ISSUABLE UPON CONVERSION THEREOF FROM IT OF THE RESALE
RESTRICTIONS REFERRED TO IN (A) ABOVE.]

              [INCLUDE IF SECURITY IS A GLOBAL SECURITY:

              THIS SECURITY IS A GLOBAL SECURITY WITHIN THE MEANING OF THE
INDENTURE HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITARY
OR A NOMINEE THEREOF. THIS SECURITY MAY NOT BE EXCHANGED IN WHOLE OR IN PART FOR
A SECURITY REGISTERED, AND NO TRANSFER OF THIS SECURITY IN WHOLE OR IN PART MAY
BE REGISTERED, IN THE NAME OF ANY PERSON OTHER THAN SUCH DEPOSITARY OR A NOMINEE
THEREOF, EXCEPT IN THE LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE.

              UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED
REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION ("DTC"),
NEW YORK, NEW YORK, TO THE COMPANY OR ITS AGENT FOR REGISTRATION OF TRANSFER,
EXCHANGE OR PAYMENT, AND ANY CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF
CEDE & CO. OR IN SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE
OF DTC, AND ANY PAYMENT IS MADE TO CEDE & CO. OR TO SUCH OTHER ENTITY AS IS
REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC, ANY TRANSFER, PLEDGE OR OTHER
USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL BECAUSE THE
REGISTERED OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.]


                           Human Genome Sciences, Inc.

                 5-1/2% Convertible Subordinated Notes due 2006

No. ____                                                   U. S. $_____________


[IF RESTRICTED GLOBAL SECURITY - CUSIP No. [                    ]]
[IF DEFINITIVE SECURITY - CUSIP No. [   ]]

              Human Genome Sciences, Inc., a corporation duly organized and
existing under the laws of the State of Delaware (herein called the "Company",
which term includes any successor Person under the Indenture hereinafter
referred to), for value received, hereby promises to pay to ________, or
registered assigns, the principal sum of


<PAGE>   23
                                                                              17


____________ United States Dollars (U.S.$________ ) on July 1, 2006, and to pay
interest thereon from June 25, 1999, or from the most recent Interest Payment
Date to which interest has been paid or duly provided for, semi-annually on July
1 and January 1 in each year, commencing January 1, 2000, at the rate of 5-1/2%
per annum, until the principal hereof is paid or made available for payment. The
interest so payable, and punctually paid or duly provided for, on any Interest
Payment Date will, as provided in such Indenture, be paid to the Person in whose
name this Security (or one or more Predecessor Securities) is registered at the
close of business on the Regular Record Date for such interest, which shall be
the June 15 or December 15 (whether or not a Business Day), as the case may be,
next preceding such Interest Payment Date. Any such interest not so punctually
paid or duly provided for will forthwith cease to be payable to the Holder on
such Regular Record Date and may either be paid to the Person in whose name this
Security (or one or more Predecessor Securities) is registered at the close of
business on a Special Record Date for the payment of such Defaulted Interest to
be fixed by the Trustee, notice whereof shall be given to Holders of Securities
not less than 10 days prior to such Special Record Date, or be paid at any time
in any other lawful manner not inconsistent with the requirements of any
securities exchange on which the Securities may be listed, and upon such notice
as may be required by such exchange, all as more fully provided in said
Indenture.

              Payment of the principal of, premium, if any, and interest
(including payment of any Additional Interest) on this Security will be made at
the Corporate Trust Office, in such coin or currency of the United States of
America as at the time of payment is legal tender for payment of public and
private debts by a U.S. Dollar check drawn on an account maintained with a bank
in the Borough of Manhattan, The City of New York; provided, however, that upon
written application by the Holder to the Security Registrar setting forth wire
instructions not later than 15 days prior to the relevant payment date (in the
case of payment of principal) or not later than the relevant Record Date (in the
case of payment of interest), such Holder may receive payment by wire transfer
of Dollars to a U.S. Dollar account (such transfers to be made only to Holders
of an aggregate principal amount in excess of U.S.$2,000,000) maintained by the
payee with a bank in the United States or in Europe and designated by the payee
to the Security Registrar.

              Reference is hereby made to the further provisions of this
Security set forth on the reverse hereof, which further provisions shall for all
purposes have the same effect as if set forth at this place.

              Unless the certificate of authentication hereon has been executed
by the Trustee referred to on the reverse hereof by manual signature, this
Security shall not be entitled to any benefit under the Indenture or be valid or
obligatory for any purpose.

              IN WITNESS WHEREOF, the Company has caused this instrument to be
duly executed.

                                       HUMAN GENOME SCIENCES, INC.


<PAGE>   24
                                                                              18


                                          By:
                                             -------------------------
                                             Name:
                                             Title:

              SECTION 2.03. Form of Reverse of Security. This Security is one of
a duly authorized issue of Securities of the Company designated as its 5-1/2%
Convertible Subordinated Notes due 2006 (herein called the "Securities"),
limited in aggregate principal amount to U.S.$100,000,000 (subject to increase
as provided in the Indenture herein defined up to an additional U.S.$25,000,000
aggregate principal amount), issued and to be issued under an Indenture, dated
as of June 25, 1999 (herein called the "Indenture"), between the Company and The
Bank of New York, as Trustee for the Holders of Securities issued under said
Indenture (herein called the "Trustee", which term includes any successor
trustee under the Indenture), to which Indenture and all indentures supplemental
thereto reference is hereby made for a statement of the respective rights,
limitations of rights, duties and immunities thereunder of the Company, the
Trustee, the holders of Senior Indebtedness and the Holders of the Securities
and of the terms upon which the Securities are, and are to be, authenticated and
delivered.

              Subject to and upon compliance with the provisions of the
Indenture, the Holder of this Security is entitled, at his option, at any time
on or before the close of business on the Business Day immediately preceding
July 1, 2006, or in case this Security or a portion hereof is called for
redemption, then in respect of this Security or such portion hereof until and
including, but (unless the Company defaults in making the payment due upon
redemption or repurchase) not after, the close of business on the Business Day
immediately preceding the Redemption Date or Repurchase Date, as the case may
be, to convert this Security (or any portion of the principal amount hereof
which is U.S.$1,000 or an integral multiple thereof), at the principal amount
hereof, or of such portion, into fully paid and non-assessable shares of Common
Stock of the Company at a conversion price equal to U.S.$52.20 aggregate
principal amount of Securities for each share of Common Stock (or at the current
adjusted conversion price if an adjustment has been made as provided in Article
XIII of the Indenture) by surrender of this Security, duly endorsed or assigned
to the Company or in blank, to the Company at its office or agency in the
Borough of Manhattan, The City of New York, accompanied by the conversion notice
hereon executed by the Holder hereof evidencing such Holder's election to
convert this Security, or if less than the entire principal amount hereof is to
be converted, the portion hereof to be converted, and, in case such surrender
shall be made during the period from the close of business on any Regular Record
Date to the opening of business on the corresponding Interest Payment Date
(unless this Security or the portion hereof being converted has been called for
redemption on a Redemption Date within such period between and including such
Regular Record Date and such Interest Payment Date), also accompanied by payment
in funds acceptable to the Company of an amount equal to the interest payable on
such Interest Payment Date on the principal amount of this Security then being
converted. Subject to the aforesaid requirement for payment of interest and, in
the case of a conversion after the close of business on any Regular Record Date
and on or before the corresponding Interest Payment Date, to the right of the
Holder of this Security (or any Predecessor Security) of record at such Regular
Record Date to receive an installment of interest (even if the Security has been
called for redemption on a Redemption Date within such period), no payment or
adjustment is to be made on conversion for interest accrued hereon or for
dividends on the Common Stock issued on conversion. No fractions of shares or
scrip representing


<PAGE>   25
                                                                              19


fractions of shares will be issued on conversion, but instead of any fractional
interest the Company shall pay a cash adjustment or round up to the next higher
whole share as provided in Article XIII of the Indenture. The conversion price
is subject to adjustment as provided in Article XIII of the Indenture. In
addition, the Indenture provides that in case of certain reclassifications,
consolidations, mergers, sales or transfers of assets or other transactions
pursuant to which the Common Stock is converted into the right to receive other
securities, cash or other property, the Indenture shall be amended, without the
consent of any Holders of Securities, so that this Security, if then
outstanding, will be convertible thereafter, during the period this Security
shall be convertible as specified above, only into the kind and amount of
securities, cash and other property receivable upon the transaction by a holder
of the number of shares of Common Stock into which this Security might have been
converted immediately prior to such transaction (assuming such holder of Common
Stock failed to exercise any rights of election and received per share the kind
and amount received per share by a plurality of non-electing shares).

              The Company will furnish to any Holder, upon request and without
charge, copies of the Certificate of Incorporation and By-laws of the Company
then in effect. Any such request may be addressed to the Company.

              The Securities are subject to redemption at the option of the
Company upon not less than 20 days' or more than 60 days' notice by mail, as a
whole or from time to time in part, at any time on or after July 6, 2002 through
June 30, 2003 at 102.75% of the principal amount, and thereafter, at the
following Redemption Prices (expressed as percentages of the principal amount),
if redeemed during the 12-month period beginning on July 1 of the years
indicated,

<TABLE>
<CAPTION>
                                                        Redemption
                    Year                                  Price
                    ----                                ----------
                    <S>                                   <C>
                    2003................................  101.83%
                    2004................................  100.92%
                    2005................................  100.00%
</TABLE>

and thereafter at a Redemption Price equal to 100% of the principal amount,
together in the case of any such redemption with accrued interest to (but not
including) the Redemption Date, but interest installments whose Stated Maturity
is on or prior to such Redemption Date will be payable to the Holders of such
Securities, or one or more Predecessor Securities, of record at the close of
business on the relevant Record Dates referred to on the face hereof, all as
provided in the Indenture.

              In certain circumstances involving a Change in Control, each
Holder shall have the right to require the Company to redeem all or part of its
Securities at a repurchase price equal to 100% of the principal amount thereof,
together with accrued and unpaid interest through the Repurchase Date.

              The Securities do not have the benefit of any sinking fund.

              In the event of redemption, conversion or repurchase of this
Security in part only, a new Security or Securities for the unredeemed,
unconverted or


<PAGE>   26
                                                                              20


unrepurchased portion hereof will be issued in the name of the Holder hereof
upon the cancellation hereof.

              Subject to certain limitations in the Indenture, at any time when
the Company is not subject to Section 13 or 15(d) of the United States
Securities Exchange Act of 1934, as amended, upon the request of a Holder or the
holder of shares of Common Stock issued upon conversion thereof, the Company
will promptly furnish or cause to be furnished Rule 144A Information (as defined
below) to such Holder or such holder of shares of Common Stock issued upon
conversion, or to a prospective purchaser of any such security designated by any
such Holder or holder of shares of Common Stock, as the case may be, to the
extent required to permit compliance by such Holder or holder of shares of
Common Stock with Rule 144A under the United States Securities Act of 1933 (the
"Securities Act"), in connection with the resale of any such security. "Rule
144A Information" shall be such information as is specified pursuant to Rule
144A(d)(4) under the Securities Act (or any successor provision thereto).

              If this Security is a Transfer Restricted Security, then the
Holder of this Security [IF THIS SECURITY IS A GLOBAL SECURITY, THEN INSERT-
(including any Person that has a beneficial interest in this Security)] and the
Common Stock issuable upon conversion thereof is entitled to the benefits of a
Registration Rights Agreement, dated as of June 25, 1999 (the "Registration
Rights Agreement") executed by the Company. If a Registration Default occurs (as
defined in the Registration Rights Agreement and in the Indenture), Additional
Interest will accrue on this Security from and including the day following such
Registration Default to but excluding the day on which such Registration Default
has been cured. Additional Interest will be paid semi-annually in arrears, with
the first semi-annual payment due on the first Interest Payment Date in respect
of the Securities following the date on which such Additional Interest begins to
accrue, and will accrue at a rate per annum equal to an additional one-half of
one percent (0.50%) of the principal amount of the Securities.

              Whenever in this Security there is a reference, in any context, to
the payment of the principal of, premium, if any, or interest on, or in respect
of, any Security, such mention shall be deemed to include mention of the payment
of Additional Interest payable as described in the preceding paragraph to the
extent that, in such context, Additional Interest is, was or would be payable in
respect of such Security and express mention of the payment of Additional
Interest (if applicable) in any provisions of this Security shall not be
construed as excluding Additional Interest in those provisions of this Security
where such express mention is not made.

              The indebtedness evidenced by this Security is, to the extent
provided in the Indenture, subordinate and subject in right of payment to the
prior payment in full of all Senior Indebtedness, and this Security is issued
subject to the provisions of the Indenture with respect thereto. Each Holder of
this Security, by accepting the same, (a) agrees to and shall be bound by such
provisions, (b) authorizes and directs the Trustee on his behalf to take such
action as may be necessary or appropriate to effectuate the subordination so
provided and (c) appoints the Trustee his attorney-in-fact for any and all such
purposes.

              If an Event of Default shall occur and be continuing, the
principal of all the Securities may be declared due and payable in the manner
and with the effect provided in Article V of the Indenture.


<PAGE>   27
                                                                              21


              The Indenture permits, with certain exceptions as therein
provided, the amendment thereof and the modification of the rights and
obligations of the Company and the rights of the Holders of the Securities under
the Indenture at any time by the Company and the Trustee with the consent of the
Holders of a majority in aggregate principal amount of the Securities at the
time Outstanding. The Indenture also contains provisions permitting the Holders
of a majority in aggregate principal amount of the Securities at the time
Outstanding, on behalf of the Holders of all the Securities, to waive compliance
by the Company with certain provisions of the Indenture and certain past
defaults under the Indenture and their consequences. Any such consent or waiver
by the Holder of this Security shall be conclusive and binding upon such Holder
and upon all future Holders of this Security and of any Security issued upon the
registration of transfer hereof or in exchange herefor or in lieu hereof,
whether or not notation of such consent or waiver is made upon this Security.

              No reference herein to the Indenture and no provision of this
Security or of the Indenture shall alter or impair the obligation of the
Company, which is absolute and unconditional, to pay the principal of, premium,
if any, and interest on (including Additional Interest) this Security at the
times, place and rate, and in the coin or currency, herein prescribed or to
convert this Security as provided in the Indenture.

              As provided in the Indenture and subject to certain limitations
therein set forth, the transfer of this Security is registrable in the Security
Register, upon surrender of this Security for registration of transfer at the
Corporate Trust Office duly endorsed by, or accompanied by a written instrument
of transfer in form satisfactory to the Company and the Security Registrar duly
executed by, the Holder hereof or his attorney duly authorized in writing, and
thereupon one or more new Securities, of authorized denominations and for the
same aggregate principal amount, will be issued to the designated transferee or
transferees.

              The Securities are issuable only in registered form without
coupons in denominations of U.S.$1,000 and any integral multiple thereof. As
provided in the Indenture and subject to certain limitations therein set forth,
Securities are exchangeable for a like aggregate principal amount of Securities
of a different authorized denomination, as requested by the Holder surrendering
the same.

              No service charge shall be made for any such registration of
transfer or exchange, but the Company may require payment of a sum sufficient to
cover any tax or other governmental charge payable in connection therewith.

              Prior to due presentment of this Security for registration of
transfer, the Company, the Trustee and any agent of the Company or the Trustee
may treat the Person in whose name this Security is registered as the owner
hereof for all purposes, whether or not payment of or on this Security is
overdue, and neither the Company, the Trustee nor any such agent shall be
affected by notice to the contrary.

              Interest on this Security shall be computed on the basis of a
360-day year of twelve 30-day months.

              All terms used in this Security which are defined in the Indenture
shall have the meanings assigned to them in the Indenture.


<PAGE>   28
                                                                              22


              THE INDENTURE AND THIS SECURITY SHALL BE GOVERNED BY AND CONSTRUED
IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK WITHOUT REGARD TO CONFLICT
OF LAWS PRINCIPLES.

              SECTION 2.04. Form of Trustee's Certificate of Authentication

              This is one of the Securities referred to in the within-mentioned
Indenture.

Dated:                                        The Bank of New York, as Trustee

                                       By
                                         ---------------------------------------
                                                            Authorized Signatory

              SECTION 2.05. Form of Conversion Notice

                                CONVERSION NOTICE

To:  Human Genome Sciences, Inc.

              The undersigned Holder of this Security hereby irrevocably
exercises the option to convert this Security, or the portion hereof (which is
U.S.$1,000 or an integral multiple thereof) below designated, at any time
following the date of original issuance thereof, into shares of Common Stock in
accordance with the terms of the Indenture referred to in this Security, and
directs that the shares issuable and deliverable upon conversion, together with
any check in payment for a fractional share and any Security representing any
unconverted principal amount hereof, be issued and delivered to the registered
owner hereof unless a different name has been provided below. If shares or any
portion of this Security not converted are to be issued in the name of a person
other than the undersigned, the undersigned will pay all transfer taxes payable
with respect thereto and is delivering herewith a certificate in proper form
certifying that the applicable restrictions on transfer have been complied with.
Any amount required to be paid by the undersigned on account of interest
accompanies this Security.


<PAGE>   29
                                                                              23


              The Applicant hereby agrees that, promptly after request of the
Company, he or it will furnish such proof in support of this certification as
the Company or the Security Registrar for the Common Stock may, from time to
time, request.

Dated:                                             -----------------------------
                                                            Signature*

                                                   -----------------------------
                                                         Signature Guaranty

If shares or Securities are to be            Principal amount to be converted
registered in the name of a Person           (if less than all):
other than the Holder, please print          $______________,000
such Person's name and address:*

- ------------------------------               -----------------------------------
          Name                                       Social Security or
                                               Taxpayer Identification Number

- ------------------------------
     Street Address


- ------------------------------
  City, State and Zip Code

* Signature(s) must be guaranteed by an eligible guarantor institution (banks,
stock brokers, savings and loan associations and credit unions with membership
in an approved signature guarantee medallion program) pursuant to Securities and
Exchange Commission Rule 17Ad-15 if shares of Common Stock are to be delivered,
or unconverted Securities are to be issued, other than to and in the name of the
registered owner.

              SECTION 2.06. Form of Certification. Whenever any certification is
required to be given to evidence compliance with certain restrictions relating
to transfers of Restricted Securities contemplated by Section 3.05(b)(iv),
Section 3.05(c) or Section 13.02, such certification shall be provided
substantially in the form of the following certificate, with only such changes
as shall be approved by the Company and the Initial Purchasers,

                              TRANSFER CERTIFICATE

              The undersigned Holder hereby certifies with respect to
U.S.$______ principal amount of the above-captioned securities presented or
surrendered on the date hereof (the "Surrendered Securities") for registration
of transfer, or for exchange or conversion where the securities issuable upon
such exchange or conversion are to be registered in a name other than that of
the undersigned Holder (each such transaction


<PAGE>   30
                                                                              24


being a "transfer"), that such transfer complies with the restrictive legend set
forth on the face of the Surrendered Securities for the reason checked below:

- ---------------       The transfer of the Surrendered Securities complies with
                      Rule 144 under the U.S. Securities Act of 1933 (the
                      "Securities Act"); or

- ---------------       The transfer of the Surrendered Securities complies with
                      Rule 144A under the Securities Act; or

- ---------------       The transfer of the Surrendered Securities is pursuant to
                      an effective registration statement under the Securities
                      Act, the prospectus delivery requirements under the
                      Securities Act have been satisfied with respect to such
                      transfer, the undersigned Holder is named as a "Selling
                      Securityholder" in the prospectus relating to such
                      registration statement, or in amendments or supplements
                      thereto, and the aggregate principal amount of
                      Surrendered Securities transferred are all or a portion
                      of the securities listed in such prospectus opposite the
                      undersigned's name.

Dated:__________________________*
*   To be dated the date of surrender.

                                               ---------------------------------
                                                         Signature

                                               If the registered owner is a
                                               corporation, partnership or
                                               fiduciary, the title of the
                                               Person signing on behalf of such
                                               registered owner must be stated.)

                                   ARTICLE III

                                 The Securities

              SECTION 3.01. Title and Terms. The aggregate principal amount of
Securities which may be authenticated and delivered under this Indenture is
limited to (a) U.S.$100,000,000 plus (b) such aggregate principal amount (which
may not exceed U.S.$25,000,000 principal amount) of Securities as may be
purchased by the Initial Purchasers to cover over-allotments pursuant to the
Purchase Agreement dated June 22, 1999, between the Company and the Initial
Purchasers, except for Securities authenticated and delivered upon registration
of transfer of, or in exchange for, or in lieu of, other Securities pursuant to
Sections 3.04, 3.05, 3.06, 9.06, 11.08, 13.02 or 14.05 and except for Securities
which, pursuant to Section 3.03, are deemed never to have been authenticated and
delivered hereunder.

              The Stated Maturity of the Securities shall be July 1, 2006, and
they shall bear interest at the rate of 5-1/2% per annum, payable semi-annually
on July 1 and January 1, commencing January 1, 2000, until the principal thereof
is paid or made available for payment.


<PAGE>   31
                                                                              25


              Payment of the principal of, premium, if any, and interest
(including payment of any Additional Interest) on this Security will be made at
the Corporate Trust Office, in such coin or currency of the United States of
America as at the time of payment is legal tender for payment of public and
private debts by a U.S. Dollar check drawn on an account maintained with a bank
in the Borough of Manhattan, The City of New York; provided, however, that upon
written application by the Holder to the Security Registrar setting forth wire
instructions not later than 15 days prior to the relevant payment date (in the
case of payment of principal) or not later than the relevant Record Date (in the
case of payment of interest), such Holder may receive payment by wire transfer
of Dollars to a U.S. Dollar account (such transfers to be made only to Holders
of an aggregate principal amount in excess of U.S.$2,000,000) maintained by the
payee with a bank in the United States or in Europe and designated by the payee
to the Security Registrar.

              The Securities shall be redeemable by the Company as provided in
Article XI.

              The Securities shall be subordinated in right of payment to the
prior payment in full of Senior Indebtedness as provided in Article XII.

              The Securities shall be convertible as provided in Article XIII.

              The Securities shall be subject to purchase by the Company at the
option of the Holder as provided in Article XIV.

              SECTION 3.02. Denominations. The Securities shall be issuable only
in registered form without coupons and only in denominations of U.S.$1,000 and
any integral multiple thereof.

              SECTION 3.03. Execution, Authentication, Delivery and Dating. The
Securities shall be executed on behalf of the Company by any of its Chairman of
the Board, its Vice Chairman of the Board, its President or one of its Vice
Presidents. The signature of any of these officers on the Securities may be
manual or facsimile.

              Securities bearing the manual or facsimile signatures of
individuals who were at any time the proper officers of the Company shall bind
the Company, notwithstanding that such individuals or any of them have ceased to
hold such offices prior to the authentication and delivery of such Securities or
did not hold such offices at the date of such Securities.

              At any time and from time to time after the execution and delivery
of this Indenture, the Company may deliver Securities of any series executed by
the Company to the Trustee for authentication, together with a Company Order for
the authentication and delivery of such Securities; and the Trustee in
accordance with such Company Order shall authenticate and deliver such
Securities as in this Indenture provided and not otherwise.

              Each Security shall be dated the date of its authentication.

              No Security shall be entitled to any benefit under this Indenture
or be valid or obligatory for any purpose unless there appears on such Security
a certificate of


<PAGE>   32
                                                                             26


authentication substantially in the form provided for herein executed by the
Trustee by manual signature, and such certificate upon any Security shall be
conclusive evidence, and the only evidence, that such Security has been duly
authenticated and delivered hereunder.

              SECTION 3.04. Global and Non-Global Securities. (a) Global
Securities. (i) Each Global Security authenticated under this Indenture shall be
registered in the name of the Depositary designated by the Company for such
Global Security or a nominee thereof and delivered to such Depositary or a
nominee thereof or custodian therefor, and each such Global Security shall
constitute a single Security for all purposes of this Indenture.

              (ii) Notwithstanding any other provision in this Indenture, no
Global Security may be exchanged in whole or in part for Securities registered,
and no transfer of a Global Security in whole or in part may be registered, in
the name of any Person other than the Depositary for such Global Security or a
nominee thereof unless (A) such Depositary (1) has notified the Company that it
is unwilling or unable to continue as Depositary for such Global Security or (2)
has ceased to be a clearing agency registered as such under the Exchange Act or
announces an intention permanently to cease business or does in fact do so, (B)
there shall have occurred and be continuing an Event of Default with respect to
such Global Security, or (C) the Company in its discretion at any time
determines not to have all the Securities represented by a Global Security. Any
Global Security exchanged pursuant to clause (i) above shall be so exchanged in
whole and not in part and any Global Security exchanged pursuant to clause (ii)
or (iii) above may be exchanged in whole or from time to time in part as
directed by the Depositary. Any Security issued in exchange for a Global
Security or any portion thereof shall be a Global Security; provided that any
such Security so issued that is registered in the name of a Person other than
the Depositary or a nominee thereof shall not be a Global Security.

              (iii) If any Global Security is to be exchanged for other
Securities or cancelled in whole, it shall be surrendered by or on behalf of the
Depositary or its nominee to the Trustee, as Security Registrar, for exchange or
cancellation as provided in this Article III. If any Global Security is to be
exchanged for other Securities or cancelled in part, or if another Security is
to be exchanged in whole or in part for a beneficial interest in any Global
Security, in each case, as provided in Section 3.05, then either (i) such Global
Security shall be so surrendered for exchange or cancellation as provided in
this Article III or (ii) the principal amount thereof shall be reduced or
increased by an amount equal to the portion thereof to be so exchanged or
cancelled, or equal to the principal amount of such other Security to be so
exchanged for a beneficial interest therein, as the case may be, by means of an
appropriate adjustment made on the records of the Trustee, as Security
Registrar, whereupon the Trustee, in accordance with the Applicable Procedures,
shall instruct the Depositary or its authorized representative to make a
corresponding adjustment to its records. Upon any such surrender or adjustment
of a Global Security, the Trustee shall, subject to Section 3.05(c) and as
otherwise provided in this Article III, authenticate and deliver any Securities
issuable in exchange for such Global Security (or any portion thereof) to or
upon the order of, and registered in such names as may be directed by, the
Depositary or its authorized representative. Upon the request of the Trustee in
connection with the occurrence of any of the events specified in the preceding
paragraph, the Company shall promptly make available to the Trustee a reasonable
supply of Securities that are not in the form of Global Securities. The Trustee
shall be entitled to rely upon any order, direction or


<PAGE>   33
                                                                              27


request of the Depositary or its authorized representative which is given or
made pursuant to this Article III if such order, direction or request is given
or made in accordance with the Applicable Procedures.

              (iv) Every Security authenticated and delivered upon registration
of transfer of, or in exchange for or in lieu of, a Global Security or any
portion thereof, whether pursuant to this Article III or otherwise, shall be
authenticated and delivered in the form of, and shall be, a Global Security,
unless such Security is registered in the name of a Person other than the
Depositary for such Global Security or a nominee thereof, in which case such
Security shall be authenticated and delivered in definitive, fully registered
form, without interest coupons.

              (v) The Depositary or its nominee, as registered owner of a Global
Security, shall be the Holder of such Global Security for all purposes under the
Indenture and the Securities, and owners of beneficial interests in a Global
Security shall hold such interests pursuant to the Applicable Procedures.
Accordingly, any such owner's beneficial interest in a Global Security will be
shown only on, and the transfer of such interest shall be effected only through,
records maintained by the Depositary or its nominee or its Agent Members and
such owners of beneficial interests in a Global Security will not be considered
the owners or holders thereof. Notwithstanding the foregoing, nothing herein
shall prevent the Company, the Trustee or any agent of the Company or the
Trustee from giving effect to any written certification, proxy or other
authorization furnished by the Depositary or such nominee, as the case may be,
or impair, as between the Depositary, its Agent Members and any other person on
whose behalf an Agent Member may act, the operation of customary practices of
such Persons governing the exercise of the rights of a holder of any Security.

              SECTION 3.05. Registration; Registration of Transfer and Exchange.
(a) The Company shall cause to be kept at the Corporate Trust Office of the
Trustee a register (the register maintained in such office and in any other
office or agency designated pursuant to Section 10.02 being herein sometimes
collectively referred to as the "Security Register") in which, subject to such
reasonable regulations as it may prescribe, the Company shall provide for the
registration of Securities and of transfers and exchanges thereof. The Trustee
is hereby appointed "Security Registrar" for the purpose of registering
Securities and transfers and exchanges thereof as herein provided. Upon
surrender for registration of transfer or exchange of any Security at an office
or agency of the Company designated pursuant to Section 10.02 for such purpose,
accompanied by a written instrument of transfer or exchange in the form provided
by the Company, the Company shall execute, and the Trustee shall authenticate
and deliver, in the name of the designated transferee or transferees, one or
more new Securities of any authorized denominations and of a like aggregate
principal amount.

              (b) Notwithstanding any other provisions of this Indenture or the
Securities, transfers and exchanges of Securities and beneficial interests in a
Global Security of the kinds specified in this Section 3.05(b) shall be made
only in accordance with this Section 3.05(b).

              (i) Transfer of Global Security. Other than as set forth in
       Section 3.04(a), a Global Security may not be transferred, in whole or in
       part, to any Person other than the Depositary or a nominee thereof, and
       no such transfer to any such other Person may be registered; provided
       that this Section 3.05(b)(i) shall not prohibit any


<PAGE>   34
                                                                              28


       transfer of a Security that is issued in exchange for a Global Security
       but is not itself a Global Security. No transfer of a Security to any
       Person shall be effective under this Indenture or the Securities unless
       and until such Security has been registered in the name of such Person.
       Nothing in this Section 3.05(b)(i) shall prohibit or render ineffective
       any transfer of a beneficial interest in a Global Security effected in
       accordance with the other provisions of this Section 3.05(b).

              (ii) Transfer of Beneficial Interests in the Global Security.
       Transfer of beneficial interests in the Global Security shall be effected
       through the Depositary, in accordance with this Indenture (including
       applicable restrictions on transfer set forth herein, if any) and the
       procedures of the Depositary therefor, if applicable.

              (iii) Other Exchanges. In the event that a Global Security or any
       portion thereof is exchanged for Securities other than Global Securities,
       such other Securities may in turn be exchanged (on transfer or otherwise)
       for Securities that are not Global Securities or for beneficial interests
       in a Global Security (if any is then outstanding) only in accordance with
       such procedures, which shall be substantially consistent with the
       provisions of this Section 3.05(b) (including the certification
       requirements set forth on the reverse of the Security intended to insure
       that transfers of beneficial interests in a Global Security comply with
       Rule 144A or Rule 144 under the Securities Act, as the case may be) and
       any Applicable Procedures, as may be from time to time adopted by the
       Company and the Trustee.

              (iv) Transfer and Exchange of Definitive Securities. When
       definitive Securities are presented to the Security Registrar with a
       request:

                     (A) to register the transfer of such definitive Securities;
              or

                     (B) to exchange such definitive Securities for an equal
              principal amount of definitive Securities of other authorized
              denominations, the Security Registrar shall register the transfer
              or make the exchange as requested if its reasonable requirements
              for such transaction are met; provided, however, that the
              definitive Securities surrendered for transfer or exchange:

                            (x) shall be duly endorsed or accompanied by a
                     written instrument of transfer in form reasonably
                     satisfactory to the Company and the Security Registrar,
                     duly executed by the Holder thereof or his attorney duly
                     authorized in writing; and

                            (y) are being transferred or exchanged pursuant to
                     an effective registration statement under the Securities
                     Act, pursuant to Section 3.05(b)(v), or pursuant to clause
                     (1), (2) or (3) below, and are accompanied by the following
                     additional information and documents, as applicable:

                                   (1) if such definitive Securities are being
                            delivered to the Security Registrar by a Holder for
                            registration in the name of such Holder, without
                            transfer, a certification from such Holder to that
                            effect (in the form set forth in Section 2.06); or


<PAGE>   35
                                                                              29


                                   (2) if such definitive Securities are being
                            transferred to the Company, a certification to that
                            effect (in the form set forth in Section 2.06); or

                                   (3) if such definitive Securities are being
                            transferred pursuant to an exemption from
                            registration in accordance with Rule 144, (i) a
                            certification to that effect (in the form set forth
                            in Section 2.06) and (ii) if the Company or Security
                            Registrar so requests, an opinion of counsel or
                            other evidence reasonably satisfactory to them as to
                            the compliance with the restrictions set forth in
                            the legend set forth in Section 2.02.

              (v) Restrictions on Transfer of a Definitive Security for a
Beneficial Interest in a Global Security. A definitive Security may not be
exchanged for a beneficial interest in a Global Security except upon
satisfaction of the requirements set forth below. Upon receipt by the Trustee of
a definitive Security, duly endorsed or accompanied by appropriate instruments
of transfer, in form satisfactory to the Trustee, together with:

                            (A) certification in the form set forth on the
                     reverse of the Security that such definitive Security is
                     being transferred to a Qualified Institutional Buyer in
                     accordance with Rule 144A; and

                            (B) written instructions directing the Trustee to
                     make, or to direct the Securities Registrar to make, an
                     adjustment on its books and records with respect to such
                     Global Security to reflect an increase in the aggregate
                     principal amount of the Securities represented by the
                     Global Security, such instructions to contain information
                     regarding the Depositary account to be credited with such
                     increase,

            then the Trustee shall cancel such definitive Security and cause, or
            direct the Securities Registrar to cause, in accordance with the
            standing instructions and procedures existing between the Depositary
            and the Securities Registrar, the aggregate principal amount of
            Securities represented by the Global Security to be increased by the
            aggregate principal amount of the definitive Security to be
            exchanged and shall credit or cause to be credited to the account of
            the Person specified in such instructions a beneficial interest in
            the Global Security equal to the principal amount of the definitive
            Security so cancelled. If no Global Securities are then outstanding,
            the Company shall issue and the Trustee shall authenticate, upon
            written order of the Company in the form of an Officers'
            Certificate, a new Global Security in the appropriate principal
            amount.

              (c) Subject to the succeeding paragraph, every Security shall be
subject to the restrictions on transfer provided in the legends required by
Section 2.02 to be applied to such Security. Whenever any Security is presented
or surrendered for registration of transfer or for exchange for a Security
registered in a name other than that of the Holder, such Security must be
accompanied by a certificate in substantially the form set forth in Section
2.06, dated the date of such surrender and signed by the Holder of such
Security, as to compliance with such restrictions on transfer. The Security
Registrar shall not be


<PAGE>   36
                                                                              30


required to accept for such registration of transfer or exchange any Security
not so accompanied by a properly completed certificate.

              (d) The restrictions imposed by the legend set forth in the first
or fourth paragraph, as the case may be, of Section 2.02 upon the
transferability of any Security shall cease and terminate when such Security has
been sold pursuant to an effective registration statement under the Securities
Act, transferred in compliance with Rule 144 under the Securities Act (or any
successor provision thereto), or after the second anniversary of the original
issuance date of the Security (or such earlier date after which the Security may
be freely transferred without registration under the Securities Act or without
being subject to transfer restrictions pursuant to the Securities Act, as may be
provided in Rule 144(k) under the Securities Act (or any successor provision
thereto) or otherwise). Any Security as to which such restrictions on transfer
shall have expired in accordance with their terms or shall have terminated may,
upon surrender of such Security for exchange to the Security Registrar in
accordance with the provisions of this Section 3.05 (accompanied, in the event
that such restrictions on transfer have terminated by reason of a transfer in
compliance with Rule 144 or any successor provision, by an opinion of counsel
having substantial experience in practice under the Securities Act and otherwise
reasonably acceptable to the Company, addressed to the Company and in form
acceptable to the Company, to the effect that the transfer of such Security has
been made in compliance with Rule 144 or such successor provision), be exchanged
for a new Security, of like tenor and aggregate principal amount, which shall
not bear the restrictive legend set forth in the first paragraph of Section
2.02. The Company shall inform the Trustee of the effective date of any
registration statement registering the Securities under the Securities Act. The
Trustee shall not be liable for any action taken or omitted to be taken by it in
good faith in accordance with the aforementioned opinion of counsel or notice of
an effective registration statement.

              (e) As used in the preceding two paragraphs (c) and (d) of this
Section 3.05, the term "transfer" encompasses any sale, pledge, transfer,
hypothecation or other disposition of any Security.

              (f) No service charge shall be made for any registration of
transfer or exchange of Securities, but the Company may require payment of a sum
sufficient to cover any tax or other governmental charge that may be imposed in
connection with any registration of transfer or exchange of Securities, other
than exchanges pursuant to Section 3.04, 9.06, 11.08, 13.02 or 14.05 not
involving any transfer.

              (g) The Company shall not be required (i) to issue, register the
transfer of or exchange any Security during a period beginning at the opening of
business 15 days before the day of the mailing of a notice of redemption of
Securities selected for redemption under Section 11.04 and ending at the close
of business on the day of such mailing, or (ii) to register the transfer of or
exchange any Security so selected for redemption in whole or in part, except the
unredeemed portion of any Security being redeemed in part.

              SECTION 3.06. Mutilated, Destroyed, Lost and Stolen Securities. If
any mutilated Security is surrendered to the Trustee, the Company shall execute
and the Trustee shall authenticate and deliver in exchange therefor a new
Security of like tenor and principal amount and bearing a number not
contemporaneously outstanding.


<PAGE>   37
                                                                              31


              If there shall be delivered to the Company and the Trustee (i)
evidence to their satisfaction of the destruction, loss or theft of any Security
and (ii) such security or indemnity as may be required by them to save each of
them and any agent of either of them harmless, then, in the absence of notice to
the Company or the Trustee that such Security has been acquired by a bona fide
purchaser, the Company shall execute and the Trustee shall authenticate and
deliver, in lieu of any such destroyed, lost or stolen Security, a new Security
of like tenor and principal amount and bearing a number not contemporaneously
outstanding.

              In case any such mutilated, destroyed, lost or stolen Security has
become or is about to become due and payable, the Company in its discretion, but
subject to any conversion rights, may, instead of issuing a new Security, pay
such Security.

              Upon the issuance, authentication and delivery by the Trustee of
any new Security under this Section 3.06, the Company may require the payment of
a sum sufficient to cover any tax or other governmental charge that may be
imposed in relation thereto and any other expenses (including the fees and
expenses of the Trustee) connected therewith.

              Every new Security issued, authenticated and delivered by the
Trustee pursuant to this Section 3.06 in lieu of any destroyed, lost or stolen
Security shall constitute an original additional contractual obligation of the
Company, whether or not the destroyed, lost or stolen Security shall be at any
time enforceable by anyone, and shall be entitled to all the benefits of this
Indenture equally and proportionately with any and all other Securities duly
issued hereunder.

              The provisions of this Section are exclusive and shall preclude
(to the extent lawful) all other rights and remedies with respect to the
replacement or payment of mutilated, destroyed, lost or stolen Securities.

              SECTION 3.07. Payment of Interest; Interest Rights Preserved.
Interest on any Security which is payable, and is punctually paid or duly
provided for, on any Interest Payment Date shall be paid to the Person in whose
name that Security (or one or more Predecessor Securities) is registered at the
close of business on the Regular Record Date for payment of such interest.

              If the Company shall be required by law to deduct any taxes from
any sum of interest payable hereunder to a Holder, (i) the Company shall make
such deductions and shall pay the full amount deducted to the relevant taxing
authority in accordance with applicable law and (ii) the amount of such
deduction shall be treated for purposes hereof as a payment of interest.

              Any interest on any Security which is payable, but is not
punctually paid or duly provided for, on any Interest Payment Date (herein
called "Defaulted Interest") shall forthwith cease to be payable to the Holder
on the relevant Regular Record Date by virtue of having been such Holder, and
such Defaulted Interest may be paid by the Company, at its election in each
case, as provided in clause (1) or (2) below:

              (1) The Company may elect to make payment of any Defaulted
       Interest to the Persons in whose names the Securities (or their
       respective Predecessor Securities) are registered at the close of
       business on a Special Record Date for the


<PAGE>   38
                                                                              32


       payment of such Defaulted Interest, which shall be fixed in the following
       manner. The Company shall notify the Trustee in writing of the amount of
       Defaulted Interest proposed to be paid on each Security and the date of
       the proposed payment, and at the same time the Company shall deposit with
       the Trustee an amount of money equal to the aggregate amount proposed to
       be paid in respect of such Defaulted Interest or shall make arrangements
       satisfactory to the Trustee for such deposit prior to the date of the
       proposed payment, such money when deposited to be held in trust for the
       benefit of the Persons entitled to such Defaulted Interest as in this
       clause (1) provided. Thereupon, the Trustee shall fix a Special Record
       Date for the payment of such Defaulted Interest which shall be not more
       than 15 days and not less than 10 days prior to the date of the proposed
       payment and not less than 10 days after the receipt by the Trustee of the
       notice of the proposed payment. The Trustee shall promptly notify the
       Company of such Special Record Date and, in the name and at the expense
       of the Company, shall cause notice of the proposed payment of such
       Defaulted Interest and the Special Record Date therefor to be mailed,
       first-class postage prepaid, to each Holder at his address as it appears
       in the Security Register, not less than 10 days prior to such Special
       Record Date. Notice of the proposed payment of such Defaulted Interest
       and the Special Record Date therefor having been so mailed, such
       Defaulted Interest shall be paid to the Persons in whose names the
       Securities (or their respective Predecessor Securities) are registered at
       the close of business on such Special Record Date and shall no longer be
       payable pursuant to the following clause (2).

              (2) The Company may make payment of any Defaulted Interest in any
       other lawful manner not inconsistent with the requirements of any
       securities exchange on which the Securities may be listed, and upon such
       notice as may be required by such exchange, if, after notice given by the
       Company to the Trustee of the proposed payment pursuant to this clause
       (2), such manner of payment shall be deemed practicable by the Trustee.

              Subject to the foregoing provisions of this Section, each Security
delivered under this Indenture upon registration of transfer of or in exchange
for or in lieu of any other Security shall carry the rights to interest accrued
and unpaid, and to accrue, which were carried by such other Security.

              In the case of any Security which is converted after any Regular
Record Date and on or prior to the corresponding Interest Payment Date, interest
on such Security whose Stated Maturity is on such Interest Payment Date shall be
deemed to continue to accrue and shall be payable on such Interest Payment Date
notwithstanding such conversion and notwithstanding that such Security may have
been called for redemption on a Redemption Date within such period, and such
interest (whether or not punctually paid or duly provided for) shall be paid to
the Person in whose name that Security (or one or more Predecessor Securities)
is registered at the close of business on such Regular Record Date. Except as
otherwise expressly provided in the immediately preceding sentence, in the case
of any Security which is converted, interest whose Stated Maturity is after the
date of conversion of such Security shall not be payable.

              SECTION 3.08. Persons Deemed Owners. Prior to due presentment of a
Security for registration of transfer, the Company, the Trustee and any agent of
the Company or the Trustee may treat the Person in whose name such Security is
registered as the owner of such Security for the purpose of receiving payment of
principal of,


<PAGE>   39
                                                                              33


premium, if any, and (subject to Section 3.07) interest on such Security and for
all other purposes whatsoever, whether or not such Security be overdue, and
neither the Company, the Trustee nor any agent of the Company or the Trustee
shall be affected by notice to the contrary.

              SECTION 3.09. Cancellation. All Securities surrendered for
payment, redemption, repurchase, registration of transfer or exchange or
conversion shall, if surrendered to any Person other than the Trustee, be
delivered to the Trustee and shall be promptly cancelled by it. The Company may
at any time deliver to the Trustee for cancellation any Securities previously
authenticated and delivered hereunder which the Company may have acquired in any
manner whatsoever, and all Securities so delivered shall be promptly cancelled
by the Trustee. No Securities shall be authenticated in lieu of or in exchange
for any Securities cancelled as provided in this Section, except as expressly
permitted by this Indenture. All cancelled Securities held by the Trustee shall
be disposed of as directed by a Company Order; provided however, the Trustee
shall not be required to destroy such cancelled Securities..

              SECTION 3.10. Computation of Interest. Interest on the Securities
shall be computed on the basis of a 360-day year of twelve 30-day months.

                                   ARTICLE IV

                           Satisfaction and Discharge

              SECTION 4.01. Satisfaction and Discharge of Indenture. This
Indenture shall upon Company request cease to be of further effect (except as to
any surviving rights of conversion, registration of transfer or exchange of
Securities herein expressly provided for), and the Trustee, at the expense of
the Company, shall execute proper instruments acknowledging satisfaction and
discharge of this Indenture, when

              (1) either

                     (A) all Securities theretofore authenticated and delivered
              (other than (i) Securities which have been destroyed, lost or
              stolen and which have been replaced or paid as provided in Section
              3.06 and (ii) Securities for whose payment money has theretofore
              been deposited in trust or segregated and held in trust by the
              Company and thereafter repaid to the Company or discharged from
              such trust, as provided in Section 10.03) have been delivered to
              the Trustee for cancellation;

              (B) all such Securities not theretofore delivered to the Trustee
       for cancellation

                     (i) have become due and payable, or

                     (ii) will become due and payable at their Stated Maturity
              within one year, or

                     (iii) are to be called for redemption within one year under
              arrangements satisfactory to the Trustee for the giving of notice
              of

<PAGE>   40
                                                                              34


              redemption by the Trustee in the name, and at the expense, of the
              Company,

and the Company, in the case of (i), (ii) or (iii) above, has deposited or
caused to be deposited irrevocably with the Trustee as trust funds in trust for
the benefit of Holders of Outstanding Securities in an amount sufficient to pay
and discharge the entire indebtedness on such Securities not theretofore
delivered to the Trustee for cancellation, for principal (and premium, if any)
and interest to the date of such deposit (in the case of Securities which have
become due and payable) or to the Stated Maturity or Redemption Date, as the
case may be;

              (2) the Company has paid or caused to be paid all other sums
       payable hereunder by the Company;

              (3) the Company has delivered to the Trustee an Officers'
       Certificate and an Opinion of Counsel, each stating that all conditions
       precedent herein provided for relating to the satisfaction and discharge
       of this Indenture have been complied with; and

              (4) no Event of Default which, with notice or lapse of time, or
       both, would become an Event of Default with respect to the Securities
       shall have occurred and be continuing on the date of such deposit.

Notwithstanding the satisfaction and discharge of this Indenture, the
obligations of the Company to the Trustee under Section 6.07, the obligations of
the Company to any Authenticating Agent under Section 6.14 and, if money shall
have been deposited with the Trustee pursuant to subclause (B) of clause (1) of
this Section, the obligations of the Trustee under Section 4.02 and the last
paragraph of Section 10.03 shall survive.

              SECTION 4.02. Application of Trust Money. Subject to the
provisions of the last paragraph of Section 10.03, all money deposited with the
Trustee pursuant to Section 4.01 shall be held in trust and applied by it, in
accordance with the provisions of the Securities and this Indenture, to the
payment, either directly or through any Paying Agent (including the Company
acting as its own Paying Agent) as the Trustee may determine, to the Persons
entitled thereto, of the principal (and premium, if any) and interest for whose
payment such money has been deposited with the Trustee. All moneys deposited
with the Trustee pursuant to Section 4.01 (and held by it or any Paying Agent)
for the payment of Securities subsequently converted shall be returned to the
Company upon Company Request.

                                    ARTICLE V

                                    Remedies

              SECTION 5.01. Events of Default. "Event of Default", wherever used
herein, means any one of the following events (whatever the reason for such
Event of Default and whether it shall be occasioned by the provisions of Article
XII or be voluntary or involuntary or be effected by operation of law or
pursuant to any judgment, decree or order of any court or any order, rule or
regulation of any administrative or governmental body):


<PAGE>   41
                                                                              35


              (1) default in the payment of any interest (including Additional
       Interest) upon any Security when it becomes due and payable, and
       continuance of such default for a period of 30 days (whether or not such
       payment is prohibited by the provisions of Article XII); or

              (2) default in the payment of the principal of (or premium, if
       any, on) any Security at its Maturity (whether or not such payment is
       prohibited by the provisions of Article XII); or

              (3) failure by the Company to provide the notice of a Change in
       Control in accordance with Section 14.02 or notice of a Change in Control
       or default in the payment of the Repurchase Price in respect of any
       Security on the Repurchase Date therefor (whether or not such payment is
       prohibited by the provisions of Article XII); or

              (4) default in the performance, or breach, of any covenant or
       warranty of the Company in this Indenture (other than a covenant or
       warranty a default in whose performance or whose breach is elsewhere in
       this Section specifically dealt with), and continuance of such default or
       breach for a period of 60 days after there has been given, by registered
       or certified mail, to the Company by the Trustee or to the Company and
       the Trustee by the Holders of at least 25% in principal amount of the
       Outstanding Securities a written notice specifying such default or breach
       and requiring it to be remedied and stating that such notice is a "Notice
       of Default" hereunder: or

              (5) a default under any bonds, debentures, notes or other
       evidences of indebtedness for money borrowed by the Company or a
       Subsidiary or under any mortgages, indentures or instruments under which
       there may be issued or by which there may be secured or evidenced any
       indebtedness for money borrowed by the Company or a Subsidiary, whether
       such indebtedness now exists or shall hereafter be created, other than
       under a Non-Recourse Obligation, which indebtedness, individually or in
       the aggregate, has a principal amount outstanding in excess of
       U.S.$10,000,000, which default shall constitute a failure to pay any
       portion of the principal of such indebtedness when due and payable after
       the expiration of any applicable grace or cure period with respect
       thereto or shall have resulted in such indebtedness becoming or being
       declared due and payable prior to the date on which it would otherwise
       have become due and payable, without such indebtedness having been
       discharged, or such acceleration having been rescinded or annulled,
       within a period of 10 days after there shall have been given, by
       registered or certified mail, to the Company by the Trustee or to the
       Company and the Trustee by the Holders of at least 25% in principal
       amount of the Outstanding Securities a written notice specifying such
       default and requiring the Company to cause such indebtedness to be
       discharged or cause such acceleration to be rescinded or annulled and
       stating that such notice is a "Notice of Default" hereunder; or

              (6) the entry by a court having jurisdiction in the premises of
       (A) a decree or order for relief in respect of the Company or a
       Subsidiary in an involuntary case or proceeding under any applicable
       Federal or State bankruptcy, insolvency, reorganization or other similar
       law or (B) a decree or order adjudging the Company or a Subsidiary
       bankrupt or insolvent, or approving as properly filed a petition seeking
       reorganization, arrangement, adjustment or composition of or in respect
       of


<PAGE>   42
                                                                              36


       the Company or a Subsidiary under any applicable Federal or State law, or
       appointing a custodian, receiver, liquidator, assignee, trustee,
       sequestrator or other similar official of the Company or a Subsidiary or
       of any substantial part of their respective properties, or ordering the
       winding up or liquidation of the affairs of the Company or a Subsidiary,
       and the continuance of any such decree or order for relief or any such
       other decree or order unstayed and in effect for a period of 60
       consecutive days; or

              (7) the commencement by the Company or a Subsidiary of a voluntary
       case or proceeding under any applicable Federal or State bankruptcy,
       insolvency, reorganization or other similar law or of any other case or
       proceeding to be adjudicated a bankrupt or insolvent, or the consent by
       either the Company or a Subsidiary to the entry of a decree or order for
       relief in respect of the Company or a Subsidiary in an involuntary case
       or proceeding under any applicable Federal or State bankruptcy,
       insolvency, reorganization or other similar law or to the commencement of
       any bankruptcy or insolvency case or proceeding against either the
       Company or a Subsidiary, or the filing by either the Company or a
       Subsidiary of a petition or answer or consent seeking reorganization or
       relief under any applicable Federal or State law, or the consent by
       either the Company or a Subsidiary to the filing of such petition or to
       the appointment of or taking possession by a custodian, receiver,
       liquidator, assignee, trustee, sequestrator or other similar official of
       the Company or a Subsidiary or of any substantial part of their
       respective properties, or the making by either the Company or a
       Subsidiary of an assignment for the benefit of creditors, or the
       admission by either the Company or a Subsidiary in writing of an
       inability to pay the debts of either the Company or a Subsidiary
       generally as they become due, or the taking of corporate action by the
       Company or a Subsidiary in furtherance of any such action.

              SECTION 5.02. Acceleration of Maturity; Rescission and
Annulment.If an Event of Default (other than an Event of Default specified in
Section 5.01(l), 5.01(2), 5.01(6) or 5.01(7)) occurs and is continuing, then in
every such case the Trustee or the Holders of not less than 25% in principal
amount of the Outstanding Securities may declare the principal of all the
Securities to be due and payable immediately, by a notice in writing to the
Company (and to the Trustee if given by Holders), and upon any such declaration
such principal and any accrued interest (including Additional Interest) thereon
shall become immediately due and payable. If an Event of Default specified in
Section 5.01(6) or 5.01(7) occurs, the principal of, and accrued interest
(including Additional Interest) on, all the Securities shall automatically, and
without any declaration or other action on the part of the Trustee or any
Holder, become immediately due and payable.

              At any time after such a declaration of acceleration has been made
and before a judgment or decree for payment of the money due has been obtained
by the Trustee as hereinafter in this Article V provided, the Holders of a
majority in principal amount of the Outstanding Securities, by written notice to
the Company and the Trustee, may rescind and annul such declaration and its
consequences if

              (1) the Company has paid or deposited with the Trustee a sum
sufficient to pay


<PAGE>   43
                                                                              37


                     (A) all overdue interest (including Additional Interest) on
              all Securities,

                     (B) the principal of (and premium, if any, on) any
              Securities which have become due otherwise than by such
              declaration of acceleration and interest thereon at the rate borne
              by the Securities,

                     (C) to the extent that payment of such interest is lawful,
              interest upon overdue interest at the rate borne by the
              Securities, and

                     (D) all sums paid or advanced by the Trustee hereunder and
              the reasonable compensation, expenses, disbursements and advances
              of the Trustee, its agents and counsel;

       and

              (2) all Events of Default, other than the nonpayment of the
       principal of Securities which have become due solely by such declaration
       of acceleration, have been cured or waived as provided in Section 5.13.

No such rescission shall affect any subsequent default or impair any right
consequent thereon.

              SECTION 5.03. Collection of Indebtedness and Suits for Enforcement
by Trustee. If

              (1) default is made in the payment of any interest on any Security
       when such interest becomes due and payable and such default continues for
       a period of 30 days, or

              (2) default is made in the payment of the principal of (or
       premium, if any, on) any Security at the Maturity thereof,

the Trustee is authorized to recover judgment in its own name and as trustee of
an express trust against the Company for the whole amount then due and payable
on such Securities for principal (and premium, if any) and interest, and, to the
extent that payment of such interest shall be legally enforceable, interest on
any overdue principal (and premium, if any) and on any overdue interest, at the
rate borne by the Securities, and, in addition thereto, such further amount as
shall be sufficient to cover the costs and expenses of collection, including the
reasonable compensation, expenses, disbursements and advances of the Trustee,
its agents and counsel.

              If an Event of Default occurs and is continuing, the Trustee may
in its discretion proceed to protect and enforce its rights and the rights of
the Holders by such appropriate judicial proceedings as the Trustee shall deem
most effectual to protect and enforce any such rights, whether for the specific
enforcement of any covenant or agreement in this Indenture or in aid of the
exercise of any power granted herein, or to enforce any other proper remedy.

              SECTION 5.04. Trustee May File Proofs of Claim. In case of any
judicial proceeding relative to the Company (or any other obligor upon the
Securities), its


<PAGE>   44
                                                                              38


property or its creditors, the Trustee shall be entitled and empowered, by
intervention in such proceeding or otherwise,

              (1) to file and prove a claim for the whole amount of principal
       and interest owing and unpaid in respect of the Securities and to file
       such other papers or documents as may be necessary or advisable in order
       to have the claims of the Trustee (including any claim for the reasonable
       compensation, expenses, disbursements and advances of the Trustee, its
       agents and counsel) and of the Holders allowed in such judicial
       proceeding, and

              (2) to collect and receive any moneys or other property payable or
       deliverable on any such claim and to distribute the same;

and any custodian, receiver, assignee, trustee, liquidator, sequestrator or
other similar official in any such judicial proceeding is hereby authorized by
each Holder to make such payments to the Trustee and, in the event that the
Trustee shall consent to the making of such payments directly to the Holders, to
pay to the Trustee any amount due it for the reasonable compensation, expenses,
disbursements and advances of the Trustee, its agents and counsel, and any other
amounts due the Trustee under Section 6.07.

              No provision of this Indenture shall be deemed to authorize the
Trustee to authorize or consent to or accept or adopt on behalf of any Holder
any plan of reorganization, arrangement, adjustment or composition affecting the
Securities or the rights of any Holder thereof or to authorize the Trustee to
vote in respect of the claim of any Holder in any such proceeding; provided,
however, that the Trustee may, on behalf of the Holders, vote for the election
of a trustee in bankruptcy or similar official and be a member of a creditors'
or other similar committee.

              SECTION 5.05. Trustee May Enforce Claims Without Possession of
Securities. All rights of action and claims under this Indenture or the
Securities may be prosecuted and enforced by the Trustee without the possession
of any of the Securities or the production thereof in any proceeding relating
thereto, and any such proceeding instituted by the Trustee shall be brought in
its own name as trustee of an express trust, and any recovery of judgment shall,
after provision for the payment of the reasonable compensation, expenses,
disbursements and advances of the Trustee, its agents and counsel, be for the
ratable benefit of the Holders of the Securities in respect of which such
judgment has been recovered.

              SECTION 5.06. Application of Money Collected. Any money collected
by the Trustee pursuant to this Article V shall be applied in the following
order, at the date or dates fixed by the Trustee and, in case of the
distribution of such money on account of principal (or premium, if any) or
interest, upon presentation of the Securities and the notation thereon of the
payment if only partially paid and upon surrender thereof if fully paid:

              FIRST: to the payment of all amounts due the Trustee under Section
       6.07;

              SECOND: subject to Article XII, to the payment of the amounts then
       due and unpaid for first, interest (including Additional Interest) on,
       and, second, for principal of (and premium, if any, on) the Securities in
       respect of which or for the


<PAGE>   45
                                                                              39


       benefit of which such money has been collected, ratably, without
       preference or priority of any kind, according to the amounts due and
       payable on such Securities for interest and principal (and premium, if
       any) respectively;

              THIRD: the balance, if any, to the Person or Persons entitled
       thereto, as their interest may appear or as a court of competent
       jurisdiction shall direct; and

              FOURTH: to the Company.

              SECTION 5.07. Limitation on Suits. No Holder of any Security shall
have any right to institute any proceeding, judicial or otherwise, with respect
to this Indenture, or for the appointment of a receiver or trustee, or for any
other remedy hereunder, unless

              (1) such Holder has previously given written notice to a
       Responsible Officer the Trustee of a continuing Event of Default;

              (2) the Holders of not less than 25% in principal amount of the
       Outstanding Securities shall have made written request to the Trustee to
       institute proceedings in respect of such Event of Default in its own name
       as Trustee hereunder;

              (3) such Holder or Holders have offered to the Trustee indemnity
       satisfactory to it (which indemnity shall not be unreasonable) against
       the costs, expenses and liabilities to be incurred in compliance with
       such request;

              (4) the Trustee for 60 days after its receipt of such notice,
       request and offer of indemnity has failed to institute any such
       proceeding; and

              (5) no direction inconsistent with such written request has been
       given to the Trustee during such 60-day period by the Holders of a
       majority in principal amount of the Outstanding Securities;

it being understood and intended that no one or more of such Holders shall have
any right in any manner whatever by virtue of, or by availing of, any provision
of this Indenture to affect, disturb or prejudice the fights of any other of
such Holders, or to obtain or to seek to obtain priority or preference over any
other of such Holders or to enforce any right under this Indenture, except in
the manner herein provided and for the equal and ratable benefit of all of such
Holders.

              SECTION 5.08. Unconditional Right of Holders To Receive Principal,
Premium and Interest and To Convert. Notwithstanding any other provision in this
Indenture, the Holder of any Security shall have the right, which is absolute
and unconditional, to receive payment of the principal of (and premium, if any)
and (subject to Section 3.07) interest on such Security on the respective Stated
Maturities expressed in such Security (or, in the case of redemption or
repurchase, on the Redemption Date or Repurchase Date, as the case may be) and
to convert such Security in accordance with Article XIII and to institute suit
for the enforcement of any such payment and right to convert, and such rights
shall not be impaired without the consent of such Holder.


<PAGE>   46
                                                                              40


              SECTION 5.09. Restoration of Rights and Remedies. If the Trustee
or any Holder has instituted any proceeding to enforce any right or remedy under
this Indenture and such proceeding has been discontinued or abandoned for any
reason, or has been determined adversely to the Trustee or to such Holder, then
and in every such case, subject to any determination in such proceeding, the
Company, the Trustee and the Holders shall be restored severally and
respectively to their former positions hereunder and thereafter all rights and
remedies of the Trustee and the Holders shall continue as though no such
proceeding had been instituted.

              SECTION 5.10. Rights and Remedies Cumulative. Except as otherwise
provided with respect to the replacement or payment of mutilated, destroyed,
lost or stolen Securities in the last paragraph of Section 3.06, no right or
remedy herein conferred upon or reserved to the Trustee or to the Holders is
intended to be exclusive of any other right or remedy, and every right and
remedy shall, to the extent permitted by law, be cumulative and in addition to
every other right and remedy given hereunder or now or hereafter existing at law
or in equity or otherwise. The assertion or employment of any right or remedy
hereunder, or otherwise, shall not prevent the concurrent assertion or
employment of any other appropriate right or remedy.

              SECTION 5.11. Delay or Omission Not Waiver. No delay or omission
of the Trustee or of any Holder of any Securities to exercise any right or
remedy accruing upon any Event of Default shall impair any such right or remedy
or constitute a waiver of any such Event of Default or an acquiescence therein.
Every right and remedy given by this Article V or by law to the Trustee or to
the Holders may be exercised from time to time, and as often as may be deemed
expedient, by the Trustee or by the Holders, as the case may be.

              SECTION 5.12. Control by Holders. The Holders of a majority in
principal amount of the Outstanding Securities shall have the right to direct
the time, method and place of conducting any proceeding for any remedy available
to the Trustee or exercising any trust or power conferred on the Trustee;
provided that

              (1) such direction shall not be in conflict with any rule of law
       or with this Indenture, and

              (2) the Trustee may take any other action deemed proper by the
       Trustee which is not inconsistent with such direction.

              SECTION 5.13. Waiver of Past Defaults. The Holders of not less
than a majority in principal amount of the Outstanding Securities may on behalf
of the Holders of all the Securities waive any past default hereunder and its
consequences, except a default

              (1) in the payment of the principal of (or premium, if any) or
       interest on any Security, or

              (2) in respect of a covenant or provision hereof which under
       Article IX cannot be modified or amended without the consent of the
       Holder of each Outstanding Security affected.


<PAGE>   47
                                                                              41


              Upon any such waiver, such default shall cease to exist, and any
Event of Default arising therefrom shall be deemed to have been cured, for every
purpose of this Indenture; but no such waiver shall extend to any subsequent or
other default or impair any right consequent thereon.

              SECTION 5.14. Undertaking for Costs. In any suit for the
enforcement of any right or remedy under this Indenture, or in any suit against
the Trustee for any action taken, suffered or omitted by it as Trustee, a court
may require any party litigant in such suit to file an undertaking to pay the
costs of such suit, and may assess costs against any such party litigant, having
due regard to the merits and good faith of the claims or defenses made by such
party litigant; provided, that this Section 5.14 shall not be deemed to
authorize any court to require such an undertaking or to make such an assessment
in any suit instituted by the Trustee or the Company or in any suit for the
enforcement of the right to convert any Security in accordance with Article
XIII.

              SECTION 5.15. Waiver of Usury, Stay or Extension Laws. The Company
covenants (to the extent that it may lawfully do so) that it will not at any
time insist upon, or plead, or in any manner whatsoever claim or take the
benefit or advantage of, any usury, stay or extension law wherever enacted, now
or at any time hereafter in force, which may affect the covenants or the
performance of this Indenture; and the Company (to the extent that it may
lawfully do so) hereby expressly waives all benefit or advantage of any such law
and covenants that it will not hinder, delay or impede the execution of any
power herein granted to the Trustee, but will suffer and permit the execution of
every such power as though no such law had been enacted.

                                   ARTICLE VI

                                   The Trustee

              SECTION 6.01. Certain Duties and Responsibilities. (a) Except
during the continuance of an Event of Default,

              (1) the Trustee undertakes to perform such duties and only such
       duties as are specifically set forth in this Indenture, and no implied
       covenants or obligations shall be read into this Indenture against the
       Trustee; and

              (2) in the absence of bad faith on its part, the Trustee may
       conclusively rely, as to the truth of the statements and the correctness
       of the opinions expressed therein, upon certificates or opinions
       furnished to the Trustee and conforming to the requirements of this
       Indenture; but in the case of any such certificates or opinions which by
       any provision hereof are specifically required to be furnished to the
       Trustee, the Trustee shall be under a duty to examine the same to
       determine whether or not they conform to the requirements of this
       Indenture.

              (b) In case an Event of Default has occurred and is continuing,
the Trustee shall exercise such of the rights and powers vested in it by this
Indenture, and use the same degree of care and skill in their exercise, as a
prudent person would exercise or use under the circumstances in the conduct of
his or her own affairs.


<PAGE>   48
                                                                              42


              (c) No provision of this Indenture shall be construed to relieve
the Trustee from liability for its own negligent action, its own negligent
failure to act, or its own willful misconduct, except that

              (1) this paragraph (c) shall not be construed to limit the effect
       of paragraph (a) of this Section;

              (2) the Trustee shall not be liable for any error of judgment made
       in good faith by a Responsible Officer, unless it shall be proved that
       the Trustee was negligent in ascertaining the pertinent facts;

              (3) the Trustee shall not be liable with respect to any action
       taken or omitted to be taken by it in good faith in accordance with the
       direction of the Holders of a majority in principal amount of the
       Outstanding Securities relating to the time, method and place of
       conducting any proceeding for any remedy available to the Trustee, or
       exercising any trust or power conferred upon the Trustee, under this
       Indenture; and

              (4) no provision of this Indenture shall require the Trustee to
       expend or risk its own funds or otherwise incur any financial liability
       in the performance of any of its duties hereunder, or in the exercise of
       any of its rights or powers.

              (d) Whether or not therein expressly so provided, every provision
of this Indenture relating to the conduct or affecting the liability of or
affording protection to the Trustee (as Trustee, Paying Agent, Authenticating
Agent or Security Registrar) shall be subject to the provisions of this Section.

              SECTION 6.02. Notice of Defaults. Within 90 days after the
occurrence of any default hereunder, the Trustee shall give the Holders, in the
manner provided in Section 1.06, notice of any default hereunder actually known
to a Responsible Officer of the Trustee; provided, however, that in the case of
any default of the character specified in Section 5.01(3), no such notice to
Holders shall be given until at least 30 days after the occurrence thereof. The
Trustee shall not be deemed to have notice of a default unless (i) the Trustee
has received written notice thereof from the Company or any Holder or (ii) a
Responsible Officer of the Trustee shall have actual knowledge thereof. For the
purpose of this Section, the term "default" means any event which is, or after
notice or lapse of time or both would become, an Event of Default.

              SECTION 6.03. Certain Rights of Trustee. Subject to the provisions
of Section 6.01:

              (a) the Trustee may conclusively rely and shall be protected in
       acting or refraining from acting upon any resolution, certificate,
       statement, instrument, opinion, report, notice, request, direction,
       consent, order, bond, debenture, note, other evidence of indebtedness or
       other paper or document believed by it to be genuine and to have been
       signed or presented by the proper party or parties;

              (b) any request or direction of the Company mentioned herein shall
       be sufficiently evidenced by a Company Request or Company Order and any
       resolution of the Board of Directors shall be sufficiently evidenced by a
       Board Resolution;


<PAGE>   49
                                                                              43


              (c) whenever in the administration of this Indenture the Trustee
       shall deem it desirable that a matter be proved or established prior to
       taking, suffering or omitting any action hereunder, the Trustee (unless
       other evidence be herein specifically prescribed) may require and, in the
       absence of bad faith on its part, conclusively rely upon an Officers'
       Certificate;

              (d) the Trustee may consult with counsel of its selection and the
       advice of such counsel or any Opinion of Counsel shall be full and
       complete authorization and protection in respect of any action taken,
       suffered or omitted by it hereunder in good faith and in reliance
       thereon;

              (e) the Trustee shall be under no obligation to exercise any of
       the rights or powers vested in it by this Indenture at the request or
       direction of any of the Holders pursuant to this Indenture, unless such
       Holders shall have offered to the Trustee security or indemnity
       satisfactory to the Trustee (which security or indemnity shall not be
       unreasonable) against the costs, expenses and liabilities which might be
       incurred by it in compliance with such request or direction;

              (f) the Trustee shall not be bound to make any investigation into
       the facts or matters stated in any resolution, certificate, statement,
       instrument, opinion, report, notice, request, direction, consent, order,
       bond, debenture, note, other evidence of indebtedness or other paper or
       document, but the Trustee, in its discretion, may make such further
       inquiry or investigation into such facts or matters as it may see fit,
       and, if the Trustee shall determine to make such further inquiry or
       investigation, it shall be entitled to examine the books, records and
       premises of the Company, personally or by agent or attorney; and

              (g) the Trustee may execute any of the trusts or powers hereunder
       or perform any duties hereunder either directly or by or through agents
       or attorneys and the Trustee shall not be responsible for any misconduct
       or negligence on the part of any agent or attorney appointed with due
       care by it hereunder.

              (h) no provision of this Indenture shall require the Trustee to
       expend or risk its own funds or otherwise incur any financial liability
       in the performance of any of its duties hereunder, or in the exercise of
       any of its rights or powers.

              SECTION 6.04. Not Responsible for Recitals or Issuance of
Securities. The recitals contained herein and in the Securities, except the
Trustee's certificates of authentication, shall be taken as the statements of
the Company, and neither the Trustee nor any Authenticating Agent assumes any
responsibility for their correctness. The Trustee makes no representations as to
the validity or sufficiency of this Indenture or of the Securities. Neither the
Trustee nor any Authenticating Agent shall be accountable for the use or
application by the Company of Securities or the proceeds thereof.

              SECTION 6.05. May Hold Securities. The Trustee, any Authenticating
Agent, any Paying Agent, any Security Registrar or any other agent of the
Company, in its individual or any other capacity, may become the owner or
pledgee of Securities and, subject to Section 6.08 and Section 6.13, may
otherwise deal with the Company with the same rights it would have if it were
not Trustee, Authenticating Agent, Paying Agent, Security Registrar or such
other agent.


<PAGE>   50
                                                                              44


              SECTION 6.06. Money Held in Trust. Money held by the Trustee in
trust hereunder need not be segregated from other funds except to the extent
required by law. The Trustee shall be under no liability for interest on any
money received by it hereunder except as otherwise agreed with the Company in
writing.

              SECTION 6.07. Compensation and Reimbursement. The Company
agrees:

              (1) to pay to the Trustee from time to time such compensation as
       shall be agreed in writing between the Company and the Trustee for all
       services rendered by it hereunder (which compensation shall not be
       limited by any provision of law in regard to the compensation of a
       trustee of an express trust);

              (2) except as otherwise expressly provided herein, to reimburse
       the Trustee upon its request for all reasonable expenses, disbursements
       and advances incurred or made by the Trustee in accordance with any
       provision of this Indenture (including the reasonable compensation and
       the expenses and disbursements of its agents and counsel), except any
       such expense, disbursement or advance as may be attributable to its
       negligence or willful misconduct;

              (3) to indemnify the Trustee for, and to hold it harmless against,
       any loss, liability or expense incurred without negligence or willful
       misconduct on its part, arising out of or in connection with the
       acceptance or administration of this trust, including the costs and
       expenses of defending itself against any claim (whether asserted by the
       Company, a Holder of Securities or any other Person) or liability in
       connection with the exercise or performance of any of its powers or
       duties hereunder. The Trustee shall notify the Company of any claim
       asserted against it for which it may seek indemnity;

              (4) all indemnifications and releases from liability granted
       hereunder to the Trustee shall extend to its officers, directors,
       employees, agents, successors and assigns;

              (5) when the Trustee incurs expenses or renders services after the
       occurrence of any Event of Default specified in Section 5.01, the
       expenses and the compensation for the services are intended to constitute
       expenses of administration under any bankruptcy, insolvency or similar
       laws; and

              (6) the obligations of the Company under this Section shall
       survive the satisfaction and discharge of this Indenture.

              SECTION 6.08. Disqualification; Conflicting Interests. If the
Trustee has or shall acquire a conflicting interest within the meaning of the
Trust Indenture Act, the Trustee shall either eliminate such interest or resign,
to the extent and in the manner provided by, and subject to the provisions of,
the Trust Indenture Act and this Indenture.

              SECTION 6.09. Corporate Trustee Required; Eligibility. There shall
at all times be a Trustee hereunder which shall be a corporation organized and
doing business under the laws of the United States, authorized under such laws
to exercise corporate trust powers, which shall have (or, in the case of a
corporation included in a bank holding company system, the related bank holding
company shall have) a combined


<PAGE>   51
                                                                              45


capital and surplus of at least U.S.$50,000,000, subject to supervision or
examination by Federal or State authority, in good standing and having an
established place of business or agency in the Borough of Manhattan, The City of
New York. If such corporation or related bank holding company publishes reports
of condition at least annually, pursuant to law or to the requirements of said
supervising or examining authority, then for the purposes of this Section, the
combined capital and surplus of such corporation or related bank holding company
shall be deemed to be its combined capital and surplus as set forth in its most
recent report of condition so published. If at any time the Trustee shall cease
to be eligible in accordance with the provisions of this Section, it shall
resign immediately in the manner and with the effect hereinafter specified in
this Article VI.

              SECTION 6.10. Resignation and Removal; Appointment of Successor.
(a) No resignation or removal of the Trustee and no appointment of a successor
Trustee pursuant to this Article shall become effective until the acceptance of
appointment by the successor Trustee in accordance with the applicable
requirements of Section 6.11.

              (b) The Trustee may resign at any time by giving written notice
thereof to the Company. If the instrument of acceptance by a successor Trustee
required by Section 6.11 shall not have been delivered to the Trustee within 30
days after the giving of such notice of resignation, the resigning Trustee may
petition any court of competent jurisdiction for the appointment of a successor
Trustee.

              (c) The Trustee may be removed at any time by Act of the Holders
of a majority in principal amount of the Outstanding Securities, delivered to
the Trustee and to the Company. If the instrument of acceptance by a successor
Trustee required by Section 6.11 shall not have been delivered to the Trustee
within 30 days after the giving of such notice of resignation, the resigning
Trustee may petition any court of competent jurisdiction for the appointment of
a successor Trustee.

              (d) If at any time:

              (1) the Trustee shall fail to comply with Section 6.08 after
       written request therefor by the Company or by any Holder who has been a
       bona fide Holder of a Security for at least six months, or

              (2) the Trustee shall cease to be eligible under Section 6.09 and
       shall fail to resign after written request therefor by the Company or by
       any such Holder, or

              (3) the Trustee shall become incapable of acting or shall be
       adjudged a bankrupt or insolvent or a receiver of the Trustee or of its
       property shall be appointed or any public officer shall take charge or
       control of the Trustee or of its property or affairs for the purpose of
       rehabilitation, conservation or liquidation,

then, in any such case, (i) the Company by a Board Resolution may remove the
Trustee, or (ii) subject to Section 5.14, any Holder who has been a bona fide
Holder of a Security for at least six months may, on behalf of himself and all
others similarly situated, petition any court of competent jurisdiction for the
removal of the Trustee and the appointment of a successor Trustee.

              (e) If the Trustee shall resign, be removed or become incapable of
acting, or if a vacancy shall occur in the office of Trustee for any cause, the
Company, by a


<PAGE>   52
                                                                              46


Board Resolution, shall promptly appoint a successor Trustee. If, within one
year after such resignation, removal or incapability, or the occurrence of such
vacancy, a successor Trustee shall be appointed by Act of the Holders of a
majority in principal amount of the Outstanding Securities delivered to the
Company and the retiring Trustee, the successor Trustee so appointed shall,
forthwith upon its acceptance of such appointment in accordance with the
applicable requirements of Section 6.11, become the successor Trustee and to
that extent supersede the successor Trustee appointed by the Company. If no
successor Trustee shall have been so appointed by the Company or the Holders and
accepted appointment in the manner required by Section 6.11, any Holder who has
been a bona fide Holder of a Security for at least six months may, on behalf of
himself and all others similarly situated, petition any court of competent
jurisdiction for the appointment of a successor Trustee.

              (f) The Company shall give notice of each resignation and each
removal of the Trustee and each appointment of a successor Trustee to all
Holders in the manner provided in Section 1.06. Each notice shall include the
name of the successor Trustee and the address of its Corporate Trust Office.

              SECTION 6.11. Acceptance of Appointment by Successor. Every
successor Trustee appointed hereunder shall execute, acknowledge and deliver to
the Company and to the retiring Trustee an instrument accepting such
appointment, and thereupon the resignation or removal of the retiring Trustee
shall become effective and such successor Trustee, without any further act, deed
or conveyance, shall become vested with all the rights, powers, trusts and
duties of the retiring Trustee; but, on the request of the Company or the
successor Trustee, such retiring Trustee shall, upon payment of its charges,
execute and deliver an instrument transferring to such successor Trustee all the
rights, powers and trusts of the retiring Trustee and shall duly assign,
transfer and deliver to such successor Trustee all property and money held by
such retiring Trustee hereunder. Upon request of any such successor Trustee, the
Company shall execute any and all instruments for more fully and certainly
vesting in and confirming to such successor Trustee all such rights, powers and
trusts.

              No successor Trustee shall accept its appointment unless at the
time of such acceptance such successor Trustee shall be qualified and eligible
under this Article VI.

              SECTION 6.12. Merger, Conversion, Consolidation or Succession to
Business. Any corporation into which the Trustee may be merged or converted or
with which it may be consolidated, or any corporation resulting from any merger,
conversion or consolidation to which the Trustee shall be a party, or any
corporation succeeding to all or substantially all the corporate trust business
of the Trustee, shall be the successor of the Trustee hereunder; provided such
corporation shall be otherwise qualified and eligible under this Article VI
without the execution or filing of any paper or any further act on the part of
any of the parties hereto. In case any Securities shall have been authenticated,
but not delivered, by the Trustee then in office, any successor by merger,
conversion or consolidation to such authenticating Trustee may adopt such
authentication and deliver the Securities so authenticated with the same effect
as if such successor Trustee had itself authenticated such Securities.

              SECTION 6.13. Preferential Collection of Claims Against Company.
If and when the Trustee shall be or become a creditor of the Company (or any
other obligor


<PAGE>   53
                                                                              47


upon the Securities), the Trustee shall be subject to the provisions of the
Trust Indenture Act regarding the collection of claims against the Company (or
any such other obligor).

              SECTION 6.14. Appointment of Authenticating Agent. The Trustee may
appoint an Authenticating Agent or Agents which shall be authorized to act on
behalf of the Trustee to authenticate Securities issued upon original issue and
upon exchange, registration of transfer, partial conversion, partial redemption,
or partial repurchase or pursuant to Section 3.06, and Securities so
authenticated shall be entitled to the benefits of this Indenture and shall be
valid and obligatory for all purposes as if authenticated by the Trustee
hereunder. Wherever reference is made in this Indenture to the authentication
and delivery of Securities by the Trustee or the Trustee's certificate of
authentication, such reference shall be deemed to include authentication and
delivery on behalf of the Trustee by an Authenticating Agent and a certificate
of authentication executed on behalf of the Trustee by an Authenticating Agent.
Each Authenticating Agent shall be acceptable to the Company and shall at all
times be a corporation organized and doing business under the laws of the United
States, authorized under such laws to act as Authenticating Agent, which shall
have (or, in the case of a corporation included in a bank holding company
system, the related bank holding company shall have) a combined capital and
surplus of not less than U.S.$50,000,000 and be subject to supervision or
examination by Federal or State authority. If such Authenticating Agent
publishes reports of condition at least annually, pursuant to law or to the
requirements of said supervising or examining authority, then, for the purposes
of this Section, the combined capital and surplus of such Authenticating Agent
or related bank holding company shall be deemed to be its combined capital and
surplus as set forth in its most recent report of condition so published. If at
any time an Authenticating Agent shall cease to be eligible in accordance with
the provisions of this Section, such Authenticating Agent shall resign
immediately in the manner and with the effect specified in this Section.

              Any corporation into which an Authenticating Agent may be merged
or converted or with which it may be consolidated, or any corporation resulting
from any merger, conversion or consolidation to which such Authenticating Agent
shall be a party, or any corporation succeeding to all or substantially all the
corporate agency or corporate trust business of an Authenticating Agent, shall
continue to be an Authenticating Agent; provided such corporation shall be
otherwise eligible under this Section, without the execution or filing of any
paper or any further act on the part of the Trustee or the Authenticating Agent.

              An Authenticating Agent may resign at any time by giving written
notice thereof to the Trustee and to the Company. The Trustee may at any time
terminate the agency of an Authenticating Agent by giving written notice thereof
to such Authenticating Agent and to the Company. Upon receiving such a notice of
resignation or upon such a termination, or in case at any time such
Authenticating Agent shall cease to be eligible in accordance with the
provisions of this Section 6.14, the Trustee may appoint a successor
Authenticating Agent which shall be acceptable to the Company and shall mail
written notice of such appointment by first-class mail, postage prepaid, to all
Holders as their names and addresses appear in the Security Register. Any
successor Authenticating Agent upon acceptance of its appointment hereunder
shall become vested with all the rights, powers and duties of its predecessor
hereunder, with like effect as if originally named as an Authenticating Agent.
No successor Authenticating Agent shall be appointed unless eligible under the
provisions of this Section 6.14.


<PAGE>   54
                                                                              48


              The Company agrees to pay to each Authenticating Agent from time
to time compensation for its services under this Section 6.14.

              If an appointment is made pursuant to this Section, the Securities
may have endorsed thereon, in addition to the Trustee's certificate of
authentication, an alternative certificate of authentication in the following
form:

              This is one of the Securities described in the within-mentioned
Indenture.

                                                  The Bank of New York
                                              -----------------------------
                                                      As Trustee


                                           By
                                             ------------------------------
                                                 As Authenticating Agent


                                           By
                                             ------------------------------
                                                  Authorized Signatory

              SECTION 6.15. Appointment of Co-Trustee. Subject to the
qualifications set forth in Section 6.09, the Trustee may appoint an additional
institution as a separate trustee or co-trustee. If the Trustee appoints an
additional institution as a separate trustee or co-trustee, each and every
remedy, power, fight, claim, demand, cause of action, immunity, estate, duty,
obligation, title, interest and lien expressed or intended by this Indenture to
be exercised by, vested in and conveyed by the Trustee with respect thereto
shall be exercisable by, vested in and conveyed to such separate trustee or
co-trustee, but only to the extent necessary to enable such separate trustee or
co-trustee to exercise such powers, rights and remedies, and every covenant and
obligation necessary for the exercise thereby by such separate trustee or
co-trustee shall run to and be enforceable by either of them. Should any
instrument in writing from the Company be required by the separate trustee or
co-trustee so appointed by the Trustee for more fully vesting in and confirming
to them such properties, rights, powers, trusts, duties and obligations, any and
all such instruments in writing shall, on request, be executed, acknowledged and
delivered by the Company. If any separate trustee or co-trustee, or a successor
to either, shall become incapable of acting or not qualified to act, resign or
be removed, all the estate, properties, rights, powers, trusts, duties and
obligations of such separate trustee or co-trustee, so far as permitted by law,
shall vest in and be exercised by the Trustee until the appointment of a
successor to such separate trustee or co-trustee. The appointment of any
separate trustee or co-trustee shall be subject to written approval of the
Company so long as no Event of Default has occurred and is continuing under this
Indenture.

                                   ARTICLE VII

                Holders' Lists and Reports by Trustee and Company

              SECTION 7.01. Company To Furnish Trustee Names and Addresses of
Holders. The Company will furnish or cause to be furnished to the Trustee


<PAGE>   55
                                                                              49


              (a) semi-annually, not more than 15 days after each Regular Record
       Date, a list, in such form as the Trustee may reasonably require, of the
       names and addresses of the Holders as of such Regular Record Date, and

              (b) at such other times as the Trustee may request in writing,
       within 30 days after the receipt by the Company of any such request, a
       list of similar form and content as of a date not more than 15 days prior
       to the time such list is furnished;

excluding from any such list names and addresses received by the Trustee in its
capacity as Security Registrar.

              SECTION 7.02. Preservation of Information; Communications to
Holders. (a) The Trustee shall preserve, in as current a form as is reasonably
practicable, the names and addresses of Holders contained in the most recent
list furnished to the Trustee as provided in Section 7.01 and the names and
addresses of Holders received by the Trustee in its capacity as Security
Registrar. The Trustee may destroy any list furnished to it as provided in
Section 7.01 upon receipt of a new list so furnished.

              (b) The rights of Holders to communicate with other Holders with
respect to their rights under this Indenture or under the Securities, and the
corresponding rights and duties of the Trustee, shall be as provided by the
Trust Indenture Act.

              (c) Every Holder of Securities, by receiving and holding the same,
agrees with the Company and the Trustee that neither the Company nor the Trustee
nor any agent of either of them shall be held accountable by reason of any
disclosure of information as to names and addresses of Holders made pursuant to
the Trust Indenture Act.

              SECTION 7.03. Reports by Trustee. (a) The Trustee shall transmit
to Holders within 60 days after May 15th of each year such reports concerning
the Trustee and its actions under this Indenture as may be required pursuant to
the Trust Indenture Act at the times and in the manner provided pursuant
thereto.

              (b) A copy of each such report shall, at the time of such
transmission to Holders, be filed by the Trustee with each stock exchange upon
which the Securities are listed, with the Commission, if applicable, and with
the Company. The Company will promptly notify the Trustee when the Securities
are listed on any stock exchange and of any delisting threrof.

              SECTION 7.04. Reports by Company. (a) The Company shall file with
the Trustee and the Commission, if applicable, and transmit to Holders, such
information, documents and other reports, and such summaries thereof, as may be
required pursuant to the Trust Indenture Act at the times and in the manner
provided pursuant to such Act; provided that any such information, documents or
reports required to be filed with the Commission pursuant to Section 13 or 15(d)
of the Exchange Act shall be filed with the Trustee within 15 days after the
same is so required to be filed with the Commission. Delivery of such reports,
information and documents to the Trustee is for informational purposes only, and
the Trustee's receipt of such shall not constitute constructive notice of any
information contained therein or determinable from


<PAGE>   56
                                                                              50


information contained therein, including the Company's compliance with any of
its covenants hereunder (as to which the Trustee is entitled to rely exclusively
on Officers' Certificates). Notwithstanding anything to the contrary contained
herein, the Trustee shall have no duty to review such documents for the purpose
of determining compliance with this Indenture.

              (b) The Company shall provide the Trustee with at least 30 days'
prior notice of any change in location of its principal executive offices or
other principal place of business.

                                  ARTICLE VIII

              Consolidation, Merger, Conveyance, Transfer or Lease

              SECTION 8.01. Company May Consolidate, etc., Only on Certain
Terms. The Company shall not consolidate with or merge into any other Person or,
directly or indirectly, convey, transfer, sell, lease or otherwise dispose of
all or substantially all of its properties and assets to any Person, and the
Company shall not permit any Person to consolidate with or merge into the
Company or convey, transfer, sell, lease or otherwise dispose of all or
substantially all of its properties and assets to the Company, unless:

              (1) in case the Company shall consolidate with or merge into
       another Person or convey, transfer or lease its properties and assets
       substantially as an entirety to any Person, the Person formed by such
       consolidation or into which the Company is merged or the Person which
       acquires by conveyance or transfer, or which leases, the properties and
       assets of the Company substantially as an entirety (i) shall be a
       corporation, partnership or trust, (ii) shall be an entity (A) organized
       and validly existing under the laws of the United States of America, any
       State thereof or the District of Columbia or (B) organized and validly
       existing under the laws of a jurisdiction outside of the United States of
       America, with its common stock, or American Depositary Shares
       representing such shares of common stock, traded on a national securities
       exchange in the United States of America or through Nasdaq and an average
       worldwide total market capitalization of its equity securities of at
       least U.S. $5 billion during the ten Trading Days immediately preceding
       the date of the Change in Control, and (iii) shall expressly assume, by
       an indenture supplemental hereto, executed and delivered to the Trustee,
       in form satisfactory to the Trustee, the due and punctual payment of the
       principal of (and premium, if any) and interest (including Additional
       Interest) on all the Securities and the performance or observance of
       every covenant of this Indenture on the part of the Company to be
       performed or observed and shall have provided for conversion rights in
       accordance with Article XIII;

              (2) immediately after giving effect to such transaction, no Event
       of Default, and no event which, after notice or lapse of time or both,
       would become an Event of Default, shall have happened and be continuing;
       and

              (3) the Company has delivered to the Trustee an Officers'
       Certificate and an Opinion of Counsel, each stating that such
       consolidation, merger, conveyance, transfer or lease and, if a
       supplemental indenture is required in connection with such


<PAGE>   57
                                                                              51


       transaction, such supplemental indenture comply with this Article VIII
       and that all conditions precedent herein provided for relating to such
       transaction have been complied with.

              SECTION 8.02. Successor Substituted. Upon any consolidation of the
Company with, or merger of the Company into, any other Person or any conveyance,
transfer or lease of the properties and assets of the Company substantially as
an entirety in accordance with Section 8.01, the successor Person formed by such
consolidation or into which the Company is merged or to which such conveyance,
transfer or lease is made shall succeed to, and be substituted for, and may
exercise every right and power of, the Company under this Indenture with the
same effect as if such successor Person had been named as the Company herein,
and thereafter, except in the case of a lease, the predecessor Person shall be
released from its obligations and covenants under this Indenture and the
Securities.

                                   ARTICLE IX

                             Supplemental Indentures

              SECTION 9.01. Supplemental Indentures Without Consent of Holders.
Without the consent of any Holders, the Company, when authorized by a Board
Resolution, and the Trustee, at any time and from time to time, may enter into
one or more indentures supplemental hereto, in form satisfactory to the Trustee,
for any of the following purposes:

              (1) to evidence the succession of another Person to the Company
       and the assumption by any such successor of the covenants of the Company
       herein and in the Securities; or

              (2) to add to the covenants of the Company for the equal and
       ratable benefit of the Holders, or to surrender any right or power herein
       conferred upon the Company; or

              (3) to secure the Company's obligations in respect of the
       Securities; or

              (4) to make provision with respect to the conversion rights of
       Holders pursuant to the requirements of Article XIII; or

              (5) to make any changes or modifications to this Indenture
       necessary in connection with the registration of any Transfer Restricted
       Securities under the Securities Act as contemplated by Section 10.11;
       provided that such action pursuant to this clause (5) shall not adversely
       affect the interests of the Holders of Securities; or

              (6) to cure any ambiguity, to correct or supplement any provision
       herein which may be inconsistent with any other provision herein, to
       correct or supplement any provision herein which limits, qualifies or
       conflicts with a provision of the Trust Indenture Act which is required
       under such Act to be a part of and govern this Indenture, in any case to
       the extent necessary to qualify this Indenture under the Trust Indenture
       Act, or to make any other provisions with respect to matters or


<PAGE>   58
                                                                              52


       questions arising under this Indenture which shall not be inconsistent
       with the provisions of this Indenture; provided that such action pursuant
       to this clause (6) shall not adversely affect the interests or legal
       rights of the Holders in any material respect.

              SECTION 9.02. Supplemental Indentures with Consent of Holders.
With the consent of the Holders of not less than a majority in principal amount
of the Outstanding Securities, by the Act of said Holders delivered to the
Company and the Trustee, the Company, when authorized by a Board Resolution, and
the Trustee may enter into an indenture or indentures supplemental hereto for
the purpose of adding any provisions to or changing in any manner or eliminating
any of the provisions of this Indenture or of modifying in any manner the rights
of the Holders under this Indenture; provided, however, that no such
supplemental indenture shall, without the consent of the Holder of each
Outstanding Security affected thereby,

              (1) change the Stated Maturity of the principal of, or any
       installment of interest on, any Security, or reduce the principal amount
       thereof or the rate of interest thereon or any premium payable upon the
       redemption thereof, or change the place of payment where, or the coin or
       currency in which, any Security or any premium or interest thereon is
       payable, or impair the right to institute suit for the enforcement of any
       such payment on or after the Stated Maturity thereof (or, in the case of
       redemption or repurchase, on or after the Redemption Date or Repurchase
       Date, as the case may be), or adversely affect the right to convert any
       Security as provided in Article XIII (except as permitted by Section
       9.01(4)), or modify the provisions of this Indenture with respect to the
       subordination of the Securities in a manner adverse to the Holders, or
       modify the redemption provisions in a manner adverse to the Holders, or
       modify the provisions relating to the Company's requirement to offer to
       repurchase Notes upon a Change in Control in a manner adverse to the
       Holders, or

              (2) modify any of the provisions of this Section 9.02, Section
       5.13 or Section 10.08, except to increase any such percentage or to
       provide that certain other provisions of this Indenture cannot be
       modified or waived without the consent of the Holder of each Outstanding
       Security affected thereby, or

              (3) modify the obligation of the Company to maintain an office or
       agency in the Borough of Manhattan, The City of New York pursuant to
       Section 10.02, or

              (4) modify any of the provisions of Section 10.09 or Section
       10.10, or

              (5) reduce the percentage in principal amount of the Outstanding
       Securities, the consent of whose Holders is required for any such
       supplemental indenture, or the consent of whose Holders is required for
       any waiver (of compliance with certain provisions of this Indenture or
       certain defaults hereunder and their consequences) provided for in this
       Indenture.

              It shall not be necessary for any Act of Holders under this
Section 9.02 to approve the particular form of any proposed supplemental
indenture, but it shall be sufficient if such Act shall approve the substance
thereof.


<PAGE>   59
                                                                              53


              SECTION 9.03. Execution of Supplemental Indentures. In executing,
or accepting the additional trusts created by, any supplemental indenture
permitted by this Article IX or the modifications thereby of the trusts created
by this Indenture, the Trustee shall receive, and (subject to Section 6.01 and
Section 6.03) shall be fully protected in relying upon, an Opinion of Counsel
stating that the execution of such supplemental indenture is authorized or
permitted by this Indenture, complies with its terms and will, upon the
execution and delivery thereof, be valid and binding upon the Company in
accordance with its terms. The Trustee may, but shall not be obligated to, enter
into any such supplemental indenture which affects the Trustee's own rights,
duties or immunities under this Indenture or otherwise.

              SECTION 9.04. Effect of Supplemental Indentures. Upon the
execution of any supplemental indenture under this Article, this Indenture shall
be modified in accordance therewith, and such supplemental indenture shall form
a part of this Indenture for all purposes; and every Holder of Securities
theretofore or thereafter authenticated and delivered hereunder shall be bound
thereby.

              SECTION 9.05. Conformity with Trust Indenture Act. Every
supplemental indenture executed pursuant to this Article shall conform to the
requirements of the Trust Indenture Act.

              SECTION 9.06. Reference in Securities to Supplemental Indentures.
Securities authenticated and delivered after the execution of any supplemental
indenture pursuant to this Article may, and shall if required by the Trustee,
bear a notation in form approved by the Trustee as to any matter provided for in
such supplemental indenture. If the Company shall so determine, new Securities
so modified as to conform, in the judgment of the Trustee and the Company, to
any such supplemental indenture may be prepared and executed by the Company and
authenticated and delivered by the Trustee in exchange for Outstanding
Securities.

                                    ARTICLE X

                                    Covenants

              SECTION 10.01. Payment of Principal, Premium and Interest. The
Company will duly and punctually pay the principal of (and premium, if any) and
interest on the Securities in accordance with the terms of the Securities and
this Indenture.

              SECTION 10.02. Maintenance of Office or Agency. The Company will
maintain in the Borough of Manhattan, The City of New York an office or agency
where Securities may be presented or surrendered for payment, where Securities
may be surrendered for registration of transfer or exchange, where Securities
may be surrendered for conversion and where notices and demands to or upon the
Company in respect of the Securities and this Indenture may be served. The
Company will give prompt written notice to the Trustee of the location, and any
change in the location, of such office or agency. If at any time the Company
shall fail to maintain any such required office or agency or shall fail to
furnish the Trustee with the address thereof, such presentations, surrenders,
notices and demands may be made or served at the Corporate Trust Office of the
Trustee or the office or agency of the Trustee in the Borough of Manhattan, The
City


<PAGE>   60
                                                                              54


of New York, and the Company hereby appoints the Trustee as its agent to receive
all such presentations, surrenders, notices and demands.

              The Company may also from time to time designate one or more other
offices or agencies (in or outside the Borough of Manhattan, The City of New
York) where the Securities may be presented or surrendered for any or all such
purposes and may from time to time rescind such designations; provided, however,
that no such designation or rescission shall in any manner relieve the Company
of its obligation to maintain an office or agency in the Borough of Manhattan,
The City of New York for such purposes. The Company will give prompt written
notice to the Trustee of any such designation or rescission and of any change in
the location of any such other office or agency.

              SECTION 10.03. Money for Security Payments To Be Held in Trust. If
the Company shall at any time act as its own Paying Agent, it will, on or before
each due date of the principal of (and premium, if any) or interest (together
with any Additional Interest in respect thereof) on any of the Securities,
segregate and hold in trust for the benefit of the Persons entitled thereto a
sum sufficient to pay the principal (and premium, if any) or interest (together
with any Additional Interest in respect thereof) so becoming due until such sums
shall be paid to such Persons or otherwise disposed of as herein provided and
will promptly notify the Trustee of its action or failure so to act.

              Whenever the Company shall have one or more Paying Agents, it
will, prior to each due date of the principal of (and premium, if any) or
interest (together with any Additional Interest in respect thereof) on any
Securities, deposit with a Paying Agent a sum sufficient to pay such amount,
such sum to be held in trust for the benefit of the Persons entitled to such
principal, premium, if any, or interest, and (unless such Paying Agent is the
Trustee) the Company will promptly notify the Trustee of its action or failure
so to act.

              The Company will cause each Paying Agent other than the Trustee to
execute and deliver to the Trustee an instrument in which such Paying Agent
shall agree with the Trustee, subject to the provisions of this Section 10.03,
that such Paying Agent will:

              (1) hold all sums held by it for the payment of the principal of,
       premium, if any, or interest on Securities in trust for the benefit of
       the Persons entitled thereto until such sums shall be paid to such
       Persons or otherwise disposed of as herein provided;

              (2) give the Trustee notice of any default by the Company (or any
       other obligor upon the Securities) in the making of any payment of
       principal, premium, if any, or interest; and

              (3) at any time during the continuance of any such default, upon
       the written request of the Trustee, forthwith pay to the Trustee all sums
       so held in trust by such Paying Agent.

              The Company may at any time, for the purpose of obtaining the
satisfaction and discharge of this Indenture or for any other purpose, pay, or
by Company Order direct any Paying Agent to pay, to the Trustee all sums held in
trust by the


<PAGE>   61
                                                                              55


Company or such Paying Agent, such sums to be held by the Trustee upon the same
trusts as those upon which such sums were held by the Company or such Paying
Agent; and, upon such payment by any Paying Agent to the Trustee, such Paying
Agent shall be released from all further liability with respect to such money.

              Any money deposited with the Trustee or any Paying Agent, or then
held by the Company, in trust for the payment of the principal of (and premium,
if any) or interest (together with any Additional Interest in respect thereof)
on any Security and remaining unclaimed for two years after such principal (and
premium, if any) or interest has become due and payable shall be paid to the
Company on Company Request, or (if then held by the Company) shall be discharged
from such trust; and the Holder of such Security shall thereafter, as an
unsecured general creditor, look only to the Company for payment thereof, and
all liability of the Trustee or such Paying Agent with respect to such trust
money, and all liability of the Company as trustee thereof, shall thereupon
cease; provided, however, that the Trustee or such Paying Agent, before being
required to make any such repayment, may at the expense of the Company cause to
be published once, in a newspaper published in the English language, customarily
published on each Business Day and of general circulation in the Borough of
Manhattan, The City of New York, notice that such money remains unclaimed and
that, after a date specified therein, which shall not be less than 30 days from
the date of such publication, any unclaimed balance of such money then remaining
will be repaid to the Company.

              SECTION 10.04. Statement by Officers as to Default. The Company
shall deliver to the Trustee, within 120 days after the end of each fiscal year
of the Company ending after the date hereof, an Officers' Certificate, stating
whether or not to the best knowledge of the signers thereof the Company is in
default in the performance and observance of any of the terms, provisions and
conditions of this Indenture (without regard to any period of grace or
requirement of notice provided hereunder) and, if the Company shall be in
default, specifying all such defaults and the nature and status thereof of which
they may have knowledge.

              SECTION 10.05. Existence. Subject to Article VIII, the Company
shall do or cause to be done all things necessary to preserve and keep in full
force and effect its existence, rights (charter and statutory) and franchises;
provided, however, that the Company shall not be required to preserve any such
right or franchise if the Board of Directors shall determine that the
preservation thereof is no longer desirable in the conduct of the business of
the Company and that the loss thereof is not disadvantageous in any material
respect to the Holders.

              SECTION 10.06. Maintenance of Properties. The Company shall cause
all properties used or useful in the conduct of its business or the business of
any Subsidiary to be maintained and kept in good condition, repair and working
order and supplied with all necessary equipment and shall cause to be made all
necessary repairs, renewals, replacements, betterments and improvements thereof,
all as in the judgment of the Company may be necessary so that the business
carried on in connection therewith may be properly and advantageously conducted
at all times; provided, however, that nothing in this Section 10.06 shall
prevent the Company from discontinuing the operation or maintenance of any of
such properties, or disposing of any of them, if such discontinuance or
disposition is, in the judgment of the Company, desirable in the conduct of its
business or the business of any Subsidiary and not disadvantageous in any
material respect to the Holders.


<PAGE>   62
                                                                              56


              SECTION 10.07. Payment of Taxes and Other Claims. The Company
shall pay or discharge or cause to be paid or discharged, before the same shall
become delinquent, (1) all taxes, assessments and governmental charges levied or
imposed upon the Company or any Subsidiary or upon the income, profits or
property of the Company or any Subsidiary, and (2) all lawful claims for labor,
materials and supplies which, if unpaid, might by law become a lien upon the
property of the Company or any Subsidiary; provided, however, that the Company
shall not be required to pay or discharge or cause to be paid or discharged any
such tax, assessment, charge or claim whose amount, applicability or validity is
being contested in good faith by appropriate proceedings.

              SECTION 10.08. Waiver of Certain Covenants. The Company may omit
in any particular instance to comply with any covenant or condition set forth in
Sections 10.05 to 10.07, inclusive, if before the time for such compliance the
Holders of at least a majority in principal amount of the Outstanding Securities
shall, by Act of such Holders, either waive such compliance in such instance or
generally waive compliance with such covenant or condition, but no such waiver
shall extend to or affect such covenant or condition except to the extent so
expressly waived, and, until such waiver shall become effective, the obligations
of the Company and the duties of the Trustee in respect of any such covenant or
condition shall remain in full force and effect.

              SECTION 10.09. Delivery of Certain Information. At any time when
the Company is not subject to Section 13 or 15(d) of the Exchange Act, upon the
request of a Holder or the holder of shares of Common Stock issued upon
conversion thereof, the Company shall promptly furnish or cause to be furnished
Rule 144A Information (as defined below) to such Holder or such holder of shares
of Common Stock issued upon conversion of Securities, or to a prospective
purchaser of any such security designated by any such Holder or holder, as the
case may be, to the extent required to permit compliance by such Holder or
holder with Rule 144A under the Securities Act in connection with the resale of
any such security. "Rule 144A Information" shall be such information as is
specified pursuant to Rule 144A(d)(4) under the Securities Act.

              SECTION 10.10. Resale of Certain Securities; Reporting Issuer.
During the period beginning on the last date of original issuance of the
Securities and ending on the date that is two years from such date, the Company
will not, and will use its best efforts not to permit any of its "affiliates"
(as defined under Rule 144 under the Securities Act or any successor provision
thereto) to, resell (x) any Securities which constitute "restricted securities"
under Rule 144 or (y) any securities into which the Securities have been
converted under this Indenture which constitute "restricted securities" under
Rule 144, that in either case have been reacquired by any of them. The Trustee
shall have no responsibility in respect of the Company's performance of its
agreement in the preceding sentence.

              SECTION 10.11. Registration Rights. (a) The Company agrees that
the Holders (and any Person that has a beneficial interest in a Security) from
time to time of Transfer Restricted Securities are entitled to the benefits of a
Registration Rights Agreement, dated as of June 25, 1999 (the "Registration
Rights Agreement"), executed by the Company. Pursuant to the Registration Rights
Agreement, the Company has agreed for the benefit of the Holders from time to
time of Transfer Restricted Securities, at the Company's expense, (i) to file
within 60 days after the first date of original issuance of the Securities, a
shelf registration statement (the "Shelf Registration


<PAGE>   63
                                                                              57


Statement") with the Commission with respect to resales of the Transfer
Restricted Securities, (ii) to use its best efforts to cause such Shelf
Registration Statement to be declared effective by the Commission not later than
120 days after the first date of original issuance of the Securities, and (iii)
to use its best efforts to maintain such Shelf Registration Statement
continuously effective under the Securities Act subject to and in accordance
with the terms of the Registration Rights Agreement.

              Additional interest (the "Additional Interest") with respect to
the Securities shall be assessed as follows if any of the following events occur
(each such event in clauses (i) through (iii) below being herein called a
"Registration Default"):

              (i) if on or prior to the 60th day after the first date of
       original issuance of the Securities the Shelf Registration Statement has
       not been filed with the Commission;

              (ii) if on or prior to the 120th day after the first date of
       original issuance of the Securities the Shelf Registration Statement has
       not been declared effective by the Commission; or

              (iii) if after the Shelf Registration Statement is declared
       effective (A) the Shelf Registration Statement thereafter ceases to be
       effective; or (B) the Shelf Registration Statement or the related
       prospectus ceases to be usable (in each case except as permitted in the
       Registration Rights Agreement) in connection with resales of Transfer
       Restricted Securities in accordance with and during the periods specified
       herein because either (1) any event occurs as a result of which the
       related prospectus forming part of such Shelf Registration Statement
       would include any untrue statement of a material fact or omit to state
       any material fact necessary to make the statements therein in the light
       of the circumstances under which they were made not misleading, or (2) it
       shall be necessary to amend such Shelf Registration Statement or
       supplement the related prospectus, to comply with the Securities Act or
       the Exchange Act or the respective rules thereunder.

              Additional Interest shall accrue on the Securities over and above
the interest set forth in the title of the Securities from and including the
date on which any such Registration Default shall occur, to but excluding the
date on which all such Registration Defaults have been cured, at a rate of 0.50%
per annum.

              (b) Any amounts of Additional Interest due pursuant to clause
(a)(i), (a)(ii) or (a)(iii) of this Section 10.11 shall be payable in cash on
the regular Interest Payment Dates. The amount of Additional Interest shall be
determined by multiplying the applicable Additional Interest rate by the
principal amount of the Securities, multiplied by a fraction, the numerator of
which is the number of days such Additional Interest rate was applicable during
such period (determined on the basis of a 360-day year comprised of twelve
30-day months), and the denominator of which is 360.

              Whenever in this Indenture there is mentioned, in any context, the
payment of the principal of, premium, if any, or interest on, or in respect of,
any Security, such mention shall be deemed to include mention of the payment of
Additional Interest provided for in this Section to the extent that, in such
context, Additional Interest are, were or would be payable in respect thereof
pursuant to the provisions of this


<PAGE>   64
                                                                              58


Section 10.11 and express mention of the payment of Additional Interest (if
applicable) in any provisions hereof shall not be construed as excluding
Additional Interest in those provisions hereof where such express mention is not
made.

                                   ARTICLE XI

                            Redemption of Securities

              SECTION 11.01. Right of Redemption. The Securities may be redeemed
at the election of the Company, as a whole or from time to time in part, at any
time on or after July 6, 2002, at the Redemption Prices specified in the form of
Security hereinbefore set forth, together with accrued interest to the
Redemption Date.

              SECTION 11.02. Applicability of Article. Redemption of Securities
at the election of the Company or otherwise, as permitted or required by any
provision of this Indenture, shall be made in accordance with such provision and
this Article XI.

              SECTION 11.03. Election to Redeem; Notice to Trustee. The election
of the Company to redeem any Securities pursuant to Section 11.01 shall be
evidenced by a Board Resolution. In case of any redemption at the election of
the Company, the Company shall, at least 45 days prior to the Redemption Date
fixed by the Company (unless a shorter notice shall be satisfactory to the
Trustee), notify the Trustee of such Redemption Date and of the principal amount
of Securities to be redeemed.

              SECTION 11.04. Selection by Trustee of Securities to Be Redeemed.
If less than all the Securities are to be redeemed, the particular Securities to
be redeemed shall be selected not less than 30 days or more than 60 days prior
to the Redemption Date by the Trustee, from the Outstanding Securities not
previously called for redemption, by lot or by such method as the Trustee shall
deem fair and appropriate in the circumstances and which may provide for the
selection for redemption of portions (equal to U.S.$1,000 or any integral
multiple thereof) of the principal amount of Securities of a denomination larger
than U.S.$1,000.

              If any Security selected for partial redemption is converted in
part before termination of the conversion right with respect to the portion of
the Security so selected, the converted portion of such Security shall be deemed
(so far as may be) to be the portion selected for redemption. Securities which
have been converted during a selection of Securities to be redeemed shall be
treated by the Trustee as Outstanding for the purpose of such selection.

              The Trustee shall promptly notify the Company and each Security
Registrar in writing of the Securities selected for redemption and, in the case
of any Securities selected for partial redemption, the principal amount thereof
to be redeemed.

              For all purposes of this Indenture, unless the context otherwise
requires, all provisions relating to the redemption of Securities shall relate,
in the case of any Securities redeemed or to be redeemed only in part, to the
portion of the principal amount of such Securities which has been or is to be
redeemed.


<PAGE>   65
                                                                              59


              SECTION 11.05. Notice of Redemption. Notice of redemption shall be
given by first-class mail, postage prepaid, mailed not less than 30 nor more
than 60 days prior to the Redemption Date, to each Holder of Securities to be
redeemed, at his address appearing in the Security Register.

              All notices of redemption shall describe the Securities, including
CUSIP number, and state:

              (1) the Redemption Date;

              (2) the Redemption Price;

              (3) if less than all the Outstanding Securities are to be
       redeemed, the identification (and, in the case of partial redemption of
       any Securities, the principal amounts) of the particular Securities to be
       redeemed;

              (4) that on the Redemption Date the Redemption Price shall become
       due and payable upon each such Security to be redeemed and that interest
       thereon shall cease to accrue on and after said date;

              (5) the conversion price, the date on which the right to convert
       the Securities to be redeemed will terminate and the place or places
       where such Securities may be surrendered for conversion; and

              (6) the place or places where such Securities are to be
       surrendered for payment of the Redemption Price.

              Notice of redemption of Securities to be redeemed at the election
of the Company shall be given by the Company or, at the Company's request, by
the Trustee in the name and at the expense of the Company, and shall be
irrevocable.

              SECTION 11.06. Deposit of Redemption Price. On or prior to any
Redemption Date, the Company shall deposit with the Trustee or with a Paying
Agent (or, if the Company is acting as its own Paying Agent, segregate and hold
in trust as provided in Section 10.03) an amount of money sufficient to pay the
Redemption Price of, and (except if the Redemption Date shall be an Interest
Payment Date) accrued interest on, all the Securities which are to be redeemed
on that date other than any Securities called for redemption on that date which
have been converted prior to the date of such deposit.

              If any Security called for redemption is converted, any money
deposited with the Trustee or with any Paying Agent or so segregated and held in
trust for the redemption of such Security shall (subject to any right of the
Holder of such Security or any Predecessor Security to receive interest as
provided in the last paragraph of Section 3.07) be paid to the Company as soon
as practicable upon Company Request or, if then held by the Company, shall be
released from such trust.

              SECTION 11.07. Securities Payable on Redemption Date. Notice of
redemption having been given as aforesaid, the Securities so to be redeemed
shall, on the Redemption Date, become due and payable at the Redemption Price
therein specified, and from and after such date (unless the Company shall
default in the payment of the


<PAGE>   66
                                                                              60


Redemption Price and accrued interest) such Securities shall cease to bear or
accrue any interest. Upon surrender of any such Security for redemption in
accordance with said notice, such Security shall be paid by the Company at the
Redemption Price, together with accrued interest to (but not including) the
Redemption Date; provided, however, that installments of interest whose Stated
Maturity is on or prior to the Redemption Date shall be payable to the Holders
of such Securities, or one or more Predecessor Securities, registered as such at
the close of business on the relevant Record Dates according to their terms and
the provisions of Section 3.07.

              If the Company shall fail to deposit the Redemption Price with the
Trustee and any Security called for redemption shall not be so paid upon
surrender thereof for redemption, the principal (and premium, if any) shall,
until paid, bear and accrue interest from the Redemption Date at the rate borne
by the Security.

              SECTION 11.08. Securities Redeemed in Part. Any Security which is
to be redeemed only in part shall be surrendered at an office or agency of the
Company designated for that purpose pursuant to Section 10.02 (with, if the
Company or the Trustee so requires, due endorsement by, or a written instrument
of transfer in form satisfactory to the Company and the Trustee duly executed
by, the Holder thereof or his attorney-in-fact duly authorized in writing), and
the Company shall execute, and the Trustee shall authenticate and deliver to the
Holder of such Security without service charge, a new Security or Securities, of
any authorized denomination as requested by such Holder, in aggregate principal
amount equal to and in exchange for the unredeemed portion of the principal
amount of the Security so surrendered.

              SECTION 11.09. Conversion Arrangement on Call for Redemption. In
connection with any redemption of Securities, the Company may arrange for the
purchase and conversion of any Securities by an agreement with one or more
investment bankers or other purchasers to purchase such Securities by paying to
the Trustee in trust for the Holders, on or before the Redemption Date, an
amount not less than the applicable Redemption Price, together with interest
accrued to the Redemption Date, of such Securities. Notwithstanding anything to
the contrary contained in this Article XI, the obligation of the Company to pay
the Redemption Price of such Securities, together with interest accrued to, but
excluding, the Redemption Date, shall be deemed to be satisfied and discharged
to the extent such amount is so paid by such purchasers. If such an agreement is
entered into, a copy of which shall be filed with the Trustee prior to the
Redemption Date, any Securities not duly surrendered for conversion by the
holders thereof may, at the option of the Company, be deemed, to the fullest
extent permitted by law, acquired by such purchasers from such holders and
(notwithstanding anything to the contrary contained in Article XIII) surrendered
by such purchasers for conversion, all as of immediately prior to the close of
business on the Redemption Date (and the right to convert any such Securities
shall be deemed to have been extended through such time), subject to payment of
the above amount as aforesaid. At the direction of the Company, the Trustee
shall hold and dispose of any such amount paid to it in the same manner as it
would monies deposited with it by the Company for the redemption of Securities.
Without the Trustee's prior written consent, no arrangement between the Company
and such purchasers for the purchase and conversion of any Securities shall
increase or otherwise affect any of the powers, duties, responsibilities or
obligations of the Trustee as set forth in this Indenture, and the Company
agrees to indemnify the Trustee from, and hold it harmless against, any loss,
liability or expense arising out of or in connection with any such arrangement
for the purchase and conversion of any Securities between the


<PAGE>   67
                                                                              61


Company and such purchasers to which the Trustee has not consented in writing,
including the costs and expenses incurred by the Trustee in the defense of any
claim or liability arising out of or in connection with the exercise or
performance of any of its powers, duties, responsibilities or obligations under
this Indenture. Nothing in the preceding sentence shall be deemed to limit the
rights and protections afforded to the Trustee in Article VI hereof, including,
but not limited to, the right to indemnification pursuant to Section 6.07.

                                   ARTICLE XII

                           Subordination of Securities

              SECTION 12.01. Securities Subordinate to Senior Indebtedness. The
Company covenants and agrees, and each Holder of a Security, by his acceptance
thereof, likewise covenants and agrees, that, to the extent and in the manner
hereinafter set forth in this Article XII, the indebtedness represented by the
Securities and the payment of the principal of (and premium, if any) and
interest on each and all of the Securities and all obligations of the Company
under this Indenture are hereby expressly made subordinate and subject in right
of payment to the prior payment in full of all Senior Indebtedness.

              SECTION 12.02. Payment over of Proceeds Upon Dissolution, Etc. In
the event of (a) any insolvency or bankruptcy case or proceeding, or any
receivership, liquidation, reorganization or other similar case or proceeding in
connection therewith, relative to the Company or to its creditors, as such, or
to its assets, or (b) any liquidation, dissolution or other winding-up of the
Company, whether voluntary or involuntary and whether or not involving
insolvency or bankruptcy, or (c) any assignment for the benefit of creditors or
any other marshalling of assets and liabilities of the Company, then and in any
such event the holders of Senior Indebtedness shall be entitled to receive
payment in full of all amounts due or to become due on or in respect of all
Senior Indebtedness, or provision shall be made for such payment in cash or cash
equivalents or otherwise in a manner satisfactory to the holders of Senior
Indebtedness, before the Holders of the Securities are entitled to receive any
payment on account of principal of (or premium, if any) or interest on the
Securities, and to that end the holders of Senior Indebtedness shall be entitled
to receive, for application to the payment thereof, any payment or distribution
of any kind or character, whether in cash, property or securities, which may be
payable or deliverable in respect of the Securities in any such case,
proceeding, dissolution, liquidation or other winding-up or event.

              In the event that, notwithstanding the foregoing provisions of
this Section 12.02, the Trustee or the Holder of any Security shall have
received any payment or distribution of assets of the Company prohibited by the
foregoing paragraph of any kind or character, whether in cash, property or
securities, before all Senior Indebtedness is paid in full or payment thereof
provided for, and if such fact shall, at or prior to the time of such payment or
distribution, have been made actually known to a Responsible Officer of the
Trustee or, as the case may be, such Holder, then and in such event such payment
or distribution shall be paid over or delivered forthwith to the trustee in
bankruptcy, receiver, liquidating trustee, custodian, assignee, agent or other
Person making payment or distribution of assets of the Company for application
to the payment of all Senior Indebtedness remaining unpaid, to the extent
necessary to pay all Senior


<PAGE>   68
                                                                              62


Indebtedness in full, after giving effect to any concurrent payment or
distribution to or for the holders of Senior Indebtedness.

              For purposes of this Article XII only, the words "cash, property
or securities" shall not be deemed to include shares of capital stock of the
Company as reorganized or readjusted, or securities of the Company or any other
corporation provided for by a plan of reorganization or readjustment which in
either case are subordinated in right of payment to all Senior Indebtedness
which may at the time be outstanding to substantially the same extent as, or to
a greater extent than, the Securities are so subordinated as provided in this
Article XII. The consolidation of the Company with, or the merger of the Company
into, another Person or the liquidation or dissolution of the Company following
the conveyance or transfer of its properties and assets substantially as an
entirety to another Person upon the terms and conditions set forth in Article
VIII shall not be deemed a dissolution, winding-up, liquidation, reorganization,
assignment for the benefit of creditors or marshalling of assets and liabilities
of the Company for the purposes of this Section 12.02 if the Person formed by
such consolidation or into which the Company is merged or which acquires by
conveyance or transfer such properties and assets substantially as an entirety,
as the case may be, shall, as a part of such consolidation, merger, conveyance
or transfer, comply with the conditions set forth in Article VIII.

              SECTION 12.03. No Payment When Senior Indebtedness in Default. (a)
In the event and during the continuation of any default in the payment of
principal of (or premium, if any) or interest on any Senior Indebtedness beyond
any applicable grace period with respect thereto (unless and until such payment
default shall have been cured or waived in writing by the holders of such Senior
Indebtedness), or (b) in the event any judicial proceeding shall be pending with
respect to any such default, then no payment shall be made by the Company on
account of principal of (or premium, if any) or interest on the Securities or on
account of the purchase or other acquisition of Securities (including pursuant
to Articles XI and XIII).

              In the event that, notwithstanding the foregoing, the Company
shall make any payment to the Trustee or the Holder of any Security prohibited
by the foregoing provisions of this Section 12.03, and if such fact shall, at or
prior to the time of such payment, have been made actually known to a
Responsible Officer of the Trustee or, as the case may be, such Holder, then and
in such event such payment shall be paid over and delivered forthwith to the
Company.

              The provisions of this Section 12.03 shall not apply to any
payment with respect to which Section 12.02 would be applicable.

              SECTION 12.04. Payment Permitted If No Default. Nothing contained
in this Article XII or elsewhere in this Indenture or in any of the Securities
shall prevent (a) the Company, at any time except during the pendency of any
case, proceeding, dissolution, liquidation or other winding-up, assignment for
the benefit of creditors or other marshalling of assets and liabilities of the
Company referred to in Section 12.02 or under the conditions described in
Section 12.03, from making payments at any time of principal of (and premium, if
any) or interest on the Securities, or (b) the application by the Trustee of any
money deposited with it hereunder to the payment of or on account of the
principal of (and premium, if any) or interest on the Securities or the
retention of such payment by the Holders, if, at the time of such application by
the Trustee, a


<PAGE>   69
                                                                              63


Responsible Officer of the Trustee did not have actual knowledge that such
payment would have been prohibited by the provisions of this Article XII.

              SECTION 12.05. Subrogation to Rights of Holders of Senior
Indebtedness. Subject to the payment in full of all Senior Indebtedness, and
until the Securities are paid in full, the Holders of the Securities shall be
subrogated (equally and ratably with the holders of all indebtedness of the
Company which by its express terms is subordinated to indebtedness of the
Company to substantially the same extent as the Securities are subordinated and
is entitled to like rights of subrogation) to the rights of the holders of such
Senior Indebtedness to receive payments and distributions of cash, property and
securities applicable to the Senior Indebtedness to the extent that payments and
distributions otherwise payable to Holders of Securities have been applied to
the payment of Senior Indebtedness as provided by this Article XII. For purposes
of such subrogation, no payments or distributions to the holders of the Senior
Indebtedness of any cash, property or securities to which the Holders of the
Securities or the Trustee would be entitled, except for the provisions of this
Article XII, and no payments over pursuant to the provisions of this Article XII
to the holders of Senior Indebtedness by Holders of the Securities or the
Trustee, shall, as among the Company, its creditors other than holders of Senior
Indebtedness and the Holders of the Securities, be deemed to be a payment or
distribution by the Company to or on account of the Senior Indebtedness.

              SECTION 12.06. Provisions Solely To Define Relative Rights. The
provisions of this Article XII are and are intended solely for the purpose of
defining the relative rights of the Holders of the Securities on the one hand
and the holders of Senior Indebtedness on the other hand. Nothing contained in
this Article XII or elsewhere in this Indenture or in the Securities is intended
to or shall

              (a) impair, as among the Company, its creditors other than holders
       of Senior Indebtedness and the Holders of the Securities, the obligation
       of the Company, which is absolute and unconditional (and which, subject
       to the rights under this Article XII of the holders of Senior
       Indebtedness, is intended to rank equally with all other general
       obligations of the Company), to pay to the Holders of the Securities the
       principal of (and premium, if any) and interest on the Securities as and
       when the same shall become due and payable in accordance with their
       terms; or

              (b) affect the relative rights against the Company of the Holders
       of the Securities and creditors of the Company other than the holders of
       Senior Indebtedness; or

              (c) prevent the Trustee or the Holder of any Security from
       exercising all remedies otherwise permitted by applicable law upon
       default under this Indenture, subject to the rights, if any, under this
       Article XII of the holders of Senior Indebtedness to receive cash,
       property and securities otherwise payable or deliverable to the Trustee
       or such Holder.

              SECTION 12.07. Trustee to Effectuate Subordination. Each Holder of
a Security by his acceptance thereof authorizes and directs the Trustee on his
behalf to take such action as may be necessary or appropriate to effectuate the
subordination provided in this Article XII and appoints the Trustee his
attorney-in-fact for any and all such purposes.


<PAGE>   70
                                                                              64


              SECTION 12.08. No Waiver of Subordination Provisions. No right of
any present or future holder of any Senior Indebtedness to enforce subordination
as herein provided shall at any time in any way be prejudiced or impaired by any
act or failure to act on the part of the Company or by any act or failure to
act, in good faith, by any such holder, or by any non-compliance by the Company
with the terms, provisions and covenants of this Indenture, regardless of any
knowledge thereof any such holder may have or be otherwise charged with.

              Without in any way limiting the generality of the foregoing
paragraph, the holders of Senior Indebtedness may, at any time and from time to
time, without the consent of or notice to the Trustee or the Holders of the
Securities, without incurring responsibility to the Holders of the Securities
and without impairing or releasing the subordination provided in this Article
XII or the obligations hereunder of the Holders of the Securities to the holders
of Senior Indebtedness, do any one or more of the following:

              (i) change the manner, place or terms of payment or extend the
       time of payment of, or renew or alter, Senior Indebtedness, or otherwise
       amend or supplement in any manner Senior Indebtedness or any instrument
       evidencing the same or any agreement under which Senior Indebtedness is
       outstanding;

              (ii) sell, exchange, release or otherwise deal with any property
       pledged, mortgaged or otherwise securing Senior Indebtedness;

              (iii) release any Person liable in any manner for the collection
       of Senior Indebtedness;

              (iv) exercise or refrain from exercising any rights against the
       Company and any other Person;

              (v) apply any and all sums received from time to time to the
       Senior Indebtedness.

              SECTION 12.09. Notice to Trustee. The Company shall give prompt
written notice to the Trustee of any fact known to the Company which would
prohibit the making of any payment to or by the Trustee in respect of the
Securities. Notwithstanding the provisions of this Article XII or any other
provision of this Indenture, the Trustee shall not be charged with knowledge of
the existence of any facts which would prohibit the making of any payment to or
by the Trustee in respect of the Securities, unless and until the Trustee shall
have received written notice thereof from the Company or a holder of Senior
Indebtedness or from any trustee therefor; and, prior to the receipt of any such
written notice, the Trustee, subject to the provisions of Section 6.01, shall be
entitled in all respects to assume that no such facts exist; provided, however,
that if the Trustee shall not have received the notice provided for in this
Section 12.09 at least two Business Days prior to the date upon which by the
terms hereof any money may become payable for any purpose (including, without
limitation, the payment of the principal of (and premium, if any) or interest on
any Security), then, anything herein contained to the contrary notwithstanding,
the Trustee shall have full power and authority to receive such money and to
apply the same to the purpose for which such money was received and shall not be
affected by any notice to the contrary which may be received by it within two
Business Days prior to such date.


<PAGE>   71
                                                                              65


              Subject to the provisions of Section 6.01, the Trustee shall be
entitled to rely on the delivery to it of a written notice by a Person
representing himself to be a holder of Senior Indebtedness (or a trustee
therefor) to establish that such notice has been given by a holder of Senior
Indebtedness (or a trustee therefor). In the event that the Trustee determines
in good faith that further evidence is required with respect to the right of any
Person as a holder of Senior Indebtedness to participate in any payment or
distribution pursuant to this Article XII, the Trustee may request such Person
to furnish evidence to the reasonable satisfaction of the Trustee as to the
amount of Senior Indebtedness held by such Person, the extent to which such
Person is entitled to participate in such payment or distribution and any other
facts pertinent to the rights of such Person under this Article XII, and if such
evidence is not furnished, the Trustee may defer any payment to such Person
pending judicial determination as to the right of such Person to receive such
payment.

              SECTION 12.10. Reliance on Judicial Order of Certificate of
Liquidating Agent. Upon any payment or distribution of assets of the Company
referred to in this Article XII, the Trustee, subject to the provisions of
Section 6.01, and the Holders of the Securities shall be entitled to rely upon
any order or decree entered by any court of competent jurisdiction in which such
insolvency, bankruptcy, receivership, liquidation, reorganization, dissolution,
winding up or similar case or proceeding is pending, or a certificate of the
trustee in bankruptcy, receiver, liquidating trustee, custodian, assignee for
the benefit of creditors, agent or other Person making such payment or
distribution, delivered to the Trustee or to the Holders of Securities, for the
purpose of ascertaining the Persons entitled to participate in such payment or
distribution, the holders of the Senior Indebtedness and other indebtedness of
the Company, the amount thereof or payable thereon, the amount or amounts paid
or distributed thereon and all other facts pertinent thereto or to this Article
XII.

              SECTION 12.11. Trustee Not Fiduciary for Holders of Senior
Indebtedness. The Trustee shall not be deemed to owe any fiduciary duty to the
holders of Senior Indebtedness and shall not be liable to any such holders if it
shall in good faith mistakenly pay over or distribute to Holders of Securities
or to the Company or to any other Person cash, property or securities to which
any holders of Senior Indebtedness shall be entitled by virtue of this Article
XII or otherwise.

              SECTION 12.12. Rights of Trustee as Holder of Senior Indebtedness;
Preservation of Trustee's Rights. The Trustee in its individual capacity shall
be entitled to all the rights set forth in this Article XII with respect to any
Senior Indebtedness which may at any time be held by it, to the same extent as
any other holder of Senior Indebtedness, and nothing in this Indenture shall
deprive the Trustee of any of its rights as such holder.

              Nothing in this Article XII shall apply to claims of, or payments
to, the Trustee under or pursuant to Section 6.07.

              SECTION 12.13. Article Applicable to Paying Agents. In case at any
time any Paying Agent other than the Trustee shall have been appointed by the
Company and be then acting hereunder, the term "Trustee" as used in this Article
XII shall in such case (unless the context otherwise requires) be construed as
extending to and including such Paying Agent within its meaning as fully for all
intents and purposes as if such Paying Agent were named in this Article XII in
addition to or in place of the Trustee;


<PAGE>   72
                                                                              66


provided, however, that Section 12.12 shall not apply to the Company or any
Affiliate of the Company if it or such Affiliate acts as Paying Agent.

              SECTION 12.14. Certain Conversions Deemed Payment. For the
purposes of this Article XII only, (1) the issuance and delivery of junior
securities upon conversion of Securities in accordance with Article XIII shall
not be deemed to constitute a payment or distribution on account of the
principal of or premium or interest on Securities or on account of the purchase
or other acquisition of Securities, and (2) the payment, issuance or delivery of
cash, property or securities (other than junior securities) upon conversion of a
Security shall be deemed to constitute payment on account of the principal of
such Security. For the purposes of this Section 12.14, the term "junior
securities" means (a) shares of any stock of any class of the Company and (b)
securities of the Company which are subordinated in right of payment to the
prior payment in full of all Senior Indebtedness which may be outstanding at the
time of issuance or delivery of such securities to substantially the same extent
as, or to a greater extent than, the Securities are so subordinated as provided
in this Article XII. Nothing contained in this Article XII or elsewhere in this
Indenture or in the Securities is intended to or shall impair, as among the
Company, its creditors other than holders of Senior Indebtedness and the Holders
of the Securities, the right, which is absolute and unconditional, of the Holder
of any Security to convert such Security in accordance with Article XIII.

                                  ARTICLE XIII

                            Conversion of Securities

              SECTION 13.01. Conversion Privilege and Conversion Price. Subject
to and upon compliance with the provisions of this Article XIII, at the option
of the Holder thereof, any Security or any portion of the principal amount
thereof which is U.S.$1,000 or an integral multiple of U.S.$1,000 may be
converted at the principal amount thereof, or of such portion thereof, into
fully paid and nonassessable shares of Common Stock of the Company at any time
following the latest date of original issuance of Securities at the conversion
price, determined as hereinafter provided, in effect at the time of conversion.
Such conversion right shall expire at the close of business on the Business Day
immediately preceding July 1, 2006, subject, in the case of conversion of any
Global Security, to any Applicable Procedures. In case a Security or portion
thereof is called for redemption at the election of the Company or the Holder
thereof exercised his right to require the Company to repurchase the Security,
such conversion right in respect of the Security or portion so called shall
expire at the close of business, New York or time, on the Business Day
immediately preceding the corresponding Redemption Date or Repurchase Date, as
the case may be, unless the Company defaults in making the payment due upon
redemption or repurchase, as the case may be (in each case subject as aforesaid
to any Applicable Procedures with respect to any Global Security).

              The price at which shares of Common Stock shall be delivered upon
conversion (herein called the "conversion price") shall be initially U.S.$52.20
per share of Common Stock. The conversion price shall be adjusted in certain
instances as provided in Section 13.04.

              In case the Company shall, by dividend or otherwise, declare or
make a distribution on its Common Stock referred to in paragraph (4) or (5) of
Section 13.04


<PAGE>   73
                                                                              67


(including, without limitation, dividends or distributions referred to in the
last sentence of paragraph (4) of Section 13.04), the Holder of each Security,
upon the conversion thereof pursuant to this Article XIII subsequent to the
close of business on the date fixed for the determination of shareholders
entitled to receive such distribution and prior to the effectiveness of the
conversion price adjustment in respect of such distribution pursuant to
paragraph (4) or (5) of Section 13.04, shall also be entitled to receive for
each share of Common Stock into which such Security is converted, the portion of
the evidences of indebtedness, shares of capital stock, securities, cash and
other property so distributed applicable to one share of Common Stock; provided,
however, that, at the election of the Company (whose election shall be evidenced
by a Board Resolution) with respect to all Holders so converting, the Company
may, in lieu of distributing to such Holder any portion of such distribution not
consisting of cash or securities of the Company, pay such Holder an amount in
cash equal to the fair market value thereof (as determined in good faith by the
Board of Directors, whose determination shall be conclusive and described in a
Board Resolution). If any conversion of a Security described in the immediately
preceding sentence occurs prior to the payment date for a distribution to
holders of Common Stock which the Holder of the Security so converted is
entitled to receive in accordance with the immediately preceding sentence, the
Company may elect (such election to be evidenced by a Board Resolution) to
distribute to such Holder a due bill for the evidences of indebtedness, shares
of capital stock, securities, cash or assets to which such Holder is so
entitled; provided that such due bill (i) meets any applicable requirements of
the principal national securities exchange or other market on which the Common
Stock is then traded and (ii) requires payment or delivery of such evidences of
indebtedness, shares of capital stock, securities, cash or assets no later than
the date of payment or delivery thereof to holders of Common Stock receiving
such distribution.

              SECTION 13.02. Exercise of Conversion Privilege. In order to
exercise the conversion privilege, the Holder of any Security to be converted
shall surrender such Security, duly endorsed or assigned to the Company or in
blank, at any office or agency maintained by the Company pursuant to Section
10.02, accompanied by (a) written notice (as set forth in Section 2.05 herein)
to the Company at such office or agency that the Holder elects to convert such
Security or, if less than the entire principal amount thereof is to be
converted, the portion thereof to be converted and (b) if shares or any portion
of such Security not to be converted are to be issued in the name of a Person
other than the Holder thereof, and the restrictions on transfer of such
Security, set forth in the first paragraph of Section 2.02 remain in effect, a
certification of the Holder as to compliance with such restrictions (as set
forth in Section 2.06).

              If the restrictions on transfer of a Security set forth in the
first paragraph of Section 2.02 remain in effect, all shares of Common Stock
delivered upon conversion thereof shall bear a restrictive legend substantially
in the form of such paragraph.

              Except as described in the last paragraph of Section 3.07, no
Holder of Securities will be entitled upon conversion thereof to any payment or
adjustment on account of accrued and unpaid interest thereon or on account of
dividends on the shares of Common Stock issued in connection therewith.
Securities surrendered for conversion during the period from the close of
business on any Regular Record Date to the opening of business on the
corresponding Interest Payment Date (except Securities called for redemption on
a Redemption Date within such period between and including such Regular Record
Date and such Interest Payment Date) must be accompanied by payment to the
Company in New York Clearing House Funds or other funds acceptable to the


<PAGE>   74
                                                                              68


Company of an amount equal to the interest payable on such Interest Payment Date
on the principal amount converted.

              Securities shall be deemed to have been converted immediately
prior to the close of business on the day of surrender of such Securities for
conversion in accordance with the foregoing provisions, and at such time the
rights of the Holders of such Securities as Holders shall cease, and the Person
or Persons entitled to receive the Common Stock issuable upon conversion shall
be treated for all purposes as the record holder or holders of such Common Stock
at such time. As promptly as practicable on or after the conversion date, the
Company shall issue and shall deliver at such office or agency a certificate or
certificates for the number of full shares of Common Stock issuable upon
conversion, together with payment in lieu of any fraction of a share as provided
in Section 13.03.

              In the case of any Security which is converted in part only, upon
such conversion the Company shall execute and the Trustee shall authenticate and
deliver to the Holder thereof, at the expense of the Company, a new Security or
Securities of authorized denominations in aggregate principal amount equal to
the unconverted portion of the principal amount of such Security. Any
requirements for notice, surrender or delivery of Securities pursuant to this
Article XIII shall, with respect to any Global Security, be subject to any
Applicable Procedures.

              SECTION 13.03. Fractions of Shares. No fractional shares of Common
Stock shall be issued upon conversion of Securities. If more than one Security
shall be surrendered for conversion at one time by the same Holder, the number
of full shares which shall be issuable upon conversion thereof shall be computed
on the basis of the aggregate principal amount of the Securities (or specified
portions thereof) so surrendered. Instead of any fractional share of Common
Stock which would otherwise be issuable upon conversion of any Security or
Securities (or specified portions thereof), the Company shall pay a cash
adjustment in respect of such fraction in an amount equal to the same fraction
of the Closing Price per share of the Common Stock at the close of business on
the day of conversion (or, if such day is not a Trading Day, on the Trading Day
immediately preceding such day) or, alternatively, the Company shall round up to
the next higher whole share.

              SECTION 13.04. Adjustment of Conversion Price. (1) In case the
Company shall pay or make a dividend or other distribution on its Common Stock
exclusively in Common Stock, the conversion price in effect at the opening of
business on the day next following the date fixed for the determination of
shareholders entitled to receive such dividend or other distribution shall be
reduced by multiplying such conversion price by a fraction of which the
numerator shall be the number of shares of Common Stock outstanding at the close
of business on the date fixed for such determination and the denominator shall
be the sum of such number of shares and the total number of shares constituting
such dividend or other distribution, such reduction to become effective
immediately after the opening of business on the day next following the date
fixed for such determination. For the purposes of this paragraph (1), the number
of shares of Common Stock at any time outstanding shall not include shares held
in the treasury of the Company but shall include shares issuable in respect of
scrip certificates issued in lieu of fractions of shares of Common Stock. The
Company shall not pay any dividend or make any distribution on shares of Common
Stock held in the treasury of the Company.


<PAGE>   75
                                                                              69


              (2) In case the Company shall pay or make a dividend or other
distribution on its Common Stock consisting exclusively of, or shall otherwise
issue to all holders of its Common Stock, rights, warrants or options entitling
the holders thereof to subscribe for or purchase shares of Common Stock at a
price per share less than the current market price per share (determined as
provided in paragraph (7) of this Section 13.04) of the Common Stock on the date
fixed for the determination of shareholders entitled to receive such rights,
warrants or options, the conversion price in effect at the opening of business
on the day following the date fixed for such determination shall be reduced by
multiplying such conversion price by a fraction of which the numerator shall be
the number of shares of Common Stock outstanding at the close of business on the
date fixed for such determination plus the number of shares of Common Stock
which the aggregate of the offering price of the total number of shares of
Common Stock so offered for subscription or purchase would purchase at such
current market price and the denominator shall be the number of shares of Common
Stock outstanding at the close of business on the date fixed for such
determination plus the number of shares of Common Stock so offered for
subscription or purchase, such reduction to become effective immediately after
the opening of business on the day following the date fixed for such
determination. For the purposes of this paragraph (2), the number of shares of
Common Stock at any time outstanding shall not include shares held in the
treasury of the Company but shall include shares issuable in respect of scrip
certificates issued in lieu of fractions of shares of Common Stock. The Company
shall not issue any rights, warrants or options in respect of shares of Common
Stock held in the treasury of the Company.

              (3) In case outstanding shares of Common Stock shall be subdivided
into a greater number of shares of Common Stock, the conversion price in effect
at the opening of business on the day following the day upon which such
subdivision becomes effective shall be proportionately reduced, and, conversely,
in case outstanding shares of Common Stock shall each be combined into a smaller
number of shares of Common Stock, the conversion price in effect at the opening
of business on the day following the day upon which such combination becomes
effective shall be proportionately increased, such reduction or increase, as the
case may be, to become effective immediately after the opening of business on
the day following the day upon which such subdivision or combination becomes
effective.

              (4) Subject to the last sentence of this paragraph (4), in case
the Company shall, by dividend or otherwise, distribute to all holders of its
Common Stock evidences of its indebtedness, shares of any class of capital
stock, securities, cash or property (excluding any rights, warrants or options
referred to in paragraph (2) of this Section 13.04, any dividend or distribution
paid exclusively in cash and any dividend or distribution referred to in
paragraph (1) of this Section 13.04), the conversion price shall be reduced so
that the same shall equal the price determined by multiplying the conversion
price in effect immediately prior to the effectiveness of the conversion price
reduction contemplated by this paragraph (4) by a fraction of which the
numerator shall be the current market price per share (determined as provided in
paragraph (7) of this Section 13.04) of the Common Stock on the date of such
effectiveness less the fair market value (as determined in good faith by the
Board of Directors, whose determination shall be conclusive and described in a
Board Resolution and shall, in the case of securities being distributed for
which prior thereto there is an actual or when issued trading market, be no less
than the value determined by reference to the average of the closing prices in
such market over the period specified in the succeeding sentence),


<PAGE>   76
                                                                              70


on the date of such effectiveness, of the portion of the evidences of
indebtedness, shares of capital stock, securities, cash and property so
distributed applicable to one share of Common Stock and the denominator shall be
such current market price per share of the Common Stock, such reduction to
become effective immediately prior to the opening of business on the day next
following the later of (a) the date fixed for the payment of such distribution
and (b) the date 20 days after the notice relating to such distribution is given
pursuant to Section 13.06(a) (such later date of (a) and (b) being referred to
as the "Reference Date"). If the Board of Directors determines the fair market
value of any distribution for purposes of this paragraph (4) by reference to the
actual or when issued trading market for any securities comprising such
distribution, it must in doing so consider the prices in such market over the
same period used in computing the current market price per share pursuant to
paragraph (7) of this Section. For purposes of this paragraph (4), any dividend
or distribution that includes shares of Common Stock or rights, warrants or
options to subscribe for or purchase shares of Common Stock shall be deemed
instead to be (a) a dividend or distribution of the evidences of indebtedness,
cash, property, shares of capital stock or securities other than such shares of
Common Stock or such rights, warrants or options (making any conversion price
reduction required by this paragraph (4)) immediately followed by (b) a dividend
or distribution of such shares of Common Stock or such rights (making any
further conversion price reduction required by paragraph (1) or (2) of this
Section 13.04, except (i) the Reference Date of such dividend or distribution as
defined in this paragraph (4) shall be substituted as "the date fixed for the
determination of shareholders entitled to receive such dividend or other
distributions", "the date fixed for the determination of shareholders entitled
to receive such rights, warrants or options" and "the date fixed for such
determination" within the meaning of paragraphs (1) and (2) of this Section
13.04 and (ii) any shares of Common Stock included in such dividend or
distribution shall not be deemed "outstanding at the close of business on the
date fixed for such determination" within the meaning of paragraph (1) of this
Section 13.04).

              (5) In case the Company shall, by dividend or otherwise, make a
distribution to all holders of its Common Stock exclusively in cash in an
aggregate amount that, together with (i) the aggregate amount of any other
distributions to all holders of its Common Stock made exclusively in cash within
the 12 months preceding the date of payment of such distribution and in respect
of which no conversion price adjustment pursuant to this paragraph (5) has been
made and (ii) the aggregate of any cash plus the fair market value (as
determined in good faith by the Board of Directors, whose determination shall be
conclusive and described in a Board Resolution), as of the expiration of the
tender or exchange offer referred to below, of consideration payable in respect
of any tender or exchange offer by the Company or a Subsidiary for all or any
portion of the Common Stock concluded within the 12 months preceding the date of
payment of such distribution and in respect of which no conversion price
adjustment pursuant to paragraph (6) of this Section 13.04 has been made,
exceeds 12.5% of the product of the current market price per share (determined
as provided in paragraph (7) of this Section 13.04) of the Common Stock on the
date fixed for shareholders entitled to receive such distribution times the
number of shares of Common Stock outstanding on such date, the conversion price
shall be reduced so that the same shall equal the price determined by
multiplying the conversion price in effect immediately prior to the
effectiveness of the conversion price reduction contemplated by this paragraph
(5) by a fraction of which the numerator shall be the current market price per
share (determined as provided in paragraph (7) of this Section 13.04) of the
Common Stock on the date of such effectiveness less the amount of cash so
distributed applicable to one share of


<PAGE>   77
                                                                              71


Common Stock and the denominator shall be such current market price per share of
the Common Stock, such reduction to become effective immediately prior to the
opening of business on the later of (a) the day following the date fixed for the
payment of such distribution and (b) the date 20 days after the notice relating
to such distribution is given pursuant to Section 13.06(a).

              (6) In case a successful tender or exchange offer made by the
Company or any Subsidiary for all or any portion of the Common Stock shall
involve an aggregate consideration having a fair market value (as determined in
good faith by the Board of Directors, whose determination shall be conclusive
and described in a Board Resolution) at the last time (the "Expiration Time")
tenders or exchanges may be made pursuant to such tender or exchange offer (as
it may be amended) that, together with (i) the aggregate of the cash plus the
fair market value (as determined in good faith by the Board of Directors, whose
determination shall be conclusive and described in a Board Resolution), as of
the expiration of the other tender or exchange offer referred to below, of
consideration payable in respect of any other tender or exchange offer by the
Company or a Subsidiary for all or any portion of the Common Stock concluded
within the preceding 12 months and in respect of which no conversion price
adjustment pursuant to this paragraph (6) has been made and (ii) the aggregate
amount of any distributions to all holders of the Common Stock made exclusively
in cash within the preceding 12 months and in respect of which no conversion
price adjustment pursuant to paragraph (5) of this Section 13.04 has been made,
exceeds 12.5% of the product of the current market price per share (determined
as provided in paragraph (7) of this Section 13.04) of the Common Stock on the
Expiration Time times the number of shares of Common Stock outstanding
(including any tendered shares) on the Expiration Time, the conversion price
shall be reduced (but not increased) so that the same shall equal the price
determined by multiplying the conversion price in effect immediately prior to
the Expiration Time by a fraction of which the numerator shall be (i) the
product of the current market price per share (determined as provided in
paragraph (7) of this Section 13.04) of the Common Stock at the Expiration Time
times the number of shares of Common Stock outstanding (including any tendered
or exchanged shares) at the Expiration Time minus (ii) the fair market value
(determined as aforesaid) of the aggregate consideration payable to shareholders
based on the acceptance (up to any maximum specified in the terms of the tender
or exchange offer) of all shares validly tendered or exchanged and not withdrawn
as of the Expiration Time (the shares deemed so accepted, up to any such
maximum, being referred to as the "Purchased Shares") and the denominator shall
be the product of (i) such current market price per share at the Expiration Time
times (ii) such number of outstanding shares at the Expiration Time less the
number of Purchased Shares, such reduction to become effective immediately prior
to the opening of business on the day following the Expiration Time.

              (7) For the purpose of any computation under this paragraph and
paragraphs (2), (4) and (5) of this Section 13.04, the current market price per
share of Common Stock on any date in question shall be deemed to be the average
of the daily Closing Prices for the 5 consecutive Trading Days selected by the
Company commencing not more than 20 Trading Days before, and ending not later
than, the date in question; provided, however, that (i) if the "ex" date (as
hereinafter defined) for any event (other than the issuance or distribution
requiring such computation) that requires an adjustment to the conversion price
pursuant to paragraph (1), (2), (3), (4), (5) or (6) above ("Other Event")
occurs on or after the 20th Trading Day prior to the date in question and prior
to the "ex" date for the issuance or distribution requiring such computation
(the "Current


<PAGE>   78
                                                                              72


Event"), the Closing Price for each Trading Day prior to the "ex" date for such
Other Event shall be adjusted by multiplying such Closing Price by the same
fraction by which the conversion price is so required to be adjusted as a result
of such Other Event, (ii) if the "ex" date for any Other Event occurs after the
"ex" date for the Current Event and on or prior to the date in question, the
Closing Price for each Trading Day on and after the "ex" date for such Other
Event shall be adjusted by multiplying such Closing Price by the reciprocal of
the fraction by which the conversion price is so required to be adjusted as a
result of such Other Event, (iii) if the "ex" date for any Other Event occurs on
the "ex" date for the Current Event, one of those events shall be deemed for
purposes of clauses (i) and (ii) of this proviso to have an "ex" date occurring
prior to the "ex" date for the other event, and (iv) if the "ex" date for the
Current Event is on or prior to the date in question, after taking into account
any adjustment required pursuant to clause (ii) of this proviso, the Closing
Price for each Trading Day on or after such "ex" date shall be adjusted by
adding thereto the amount of any cash and the fair market value on the date in
question (as determined in good faith by the Board of Directors in a manner
consistent with any determination of such value for purposes of paragraph (4) or
(5) of this Section 13.04, whose determination shall be conclusive and described
in a Board Resolution) of the portion of the rights, warrants, options,
evidences of indebtedness, shares of capital stock, securities, cash or property
being distributed applicable to one share of Common Stock. For the purpose of
any computation under paragraph (6) of this Section 13.04, the current market
price per share of Common Stock on any date in question shall be deemed to be
the average of the daily Closing Prices for the 5 consecutive Trading Days
selected by the Company commencing on or after the latest (the "Commencement
Date") of (i) the date 20 Trading Days before the date in question, (ii) the
date of commencement of the tender or exchange offer requiring such computation
and (iii) the date of the last amendment, if any, of such tender or exchange
offer involving a change in the maximum number of shares for which tenders are
sought or a change in the consideration offered, and ending not later than the
date of the Expiration Time of such tender or exchange offer (or, if such
Expiration Time occurs before the close of trading on a Trading Day, not later
than the Trading Day immediately preceding the date of such Expiration Time);
provided, however, that if the "ex" date for any Other Event (other than the
tender or exchange offer requiring such computation) occurs on or after the
Commencement Date and on or prior to the date of the Expiration Time for the
tender or exchange offer requiring such computation, the Closing Price for each
Trading Day prior to the "ex" date for such Other Event shall be adjusted by
multiplying such Closing Price by the same fraction by which the conversion
price is so required to be adjusted as a result of such other event. For
purposes of this paragraph, the term "ex" date, (i) when used with respect to
any issuance or distribution, means the first date on which the Common Stock
trades regular way on the relevant exchange or in the relevant market from which
the Closing Price was obtained without the right to receive such issuance or
distribution, (ii) when used with respect to any subdivision or combination of
shares of Common Stock, means the first date on which the Common Stock trades
regular way on such exchange or in such market after the time at which such
subdivision or combination becomes effective, and (iii) when used with respect
to any tender or exchange offer means the first date on which the Common Stock
trades regular way on such exchange or in such market after the Expiration Time
of such tender or exchange offer.

              (8) The Company may make such reductions in the conversion price,
in addition to those required by paragraphs (1), (2), (3), (4), (5) and (6) of
this Section, as it considers to be advisable in order that any event treated
for Federal income tax purposes


<PAGE>   79
                                                                              73


as a dividend of stock or stock rights shall not be taxable to the recipients,
or to diminish the amount of such tax payable.

              (9) No adjustment in the conversion price shall be required unless
such adjustment would require an increase or decrease of at least 1% in the
conversion price; provided, however, that any adjustments which by reason of
this paragraph (9) are not required to be made shall be carried forward and
taken into account in any subsequent adjustment.

              (10) In the event that the Company distributes rights or warrants
(other than those referred to in paragraph (2) above) pro rata to holders of
Common Stock, so long as any such rights or warrants have not expired or been
redeemed by the Company, the Company shall make proper provision so that the
Holder of any Security surrendered for conversion will be entitled to receive
upon such conversion, in addition to the Conversion Shares, a number of rights
and warrants to be determined as follows: (i) if such conversion occurs on or
prior to the date for the distribution to the holders of rights or warrants of
separate certificates evidencing such rights or warrants (the "Distribution
Date"), the same number of rights or warrants to which a holder of a number of
shares of Common Stock equal to the number of Conversion Shares is entitled at
the time of such conversion in accordance with the terms and provisions of and
applicable to the rights or warrants, and (ii) if such conversion occurs after
such Distribution Date, the same number of rights or warrants to which a holder
of the number of shares of Common Stock into which the principal amount of such
Security so converted was convertible immediately prior to such Distribution
Date would have been entitled on such Distribution Date in accordance with the
terms and provisions of and applicable to the rights or warrants.

              SECTION 13.05. Notice of Adjustments of Conversion Price. Whenever
the conversion price is adjusted as herein provided:

              (a) the Company shall compute the adjusted conversion price in
       accordance with Section 13.04 and shall prepare a certificate signed by
       the Treasurer of the Company setting forth the adjusted conversion price
       and showing in reasonable detail the facts upon which such adjustment is
       based, and such certificate shall forthwith be filed (with a copy to the
       Trustee) at each office or agency maintained for the purpose of
       conversion of Securities pursuant to Section 10.02; and

              (b) a notice stating that the conversion price has been adjusted
       and setting forth the adjusted conversion price shall forthwith be
       required, and as soon as practicable after it is required, such notice
       shall be mailed by the Company to all Holders at their last addresses as
       they shall appear in the Security Register.

              SECTION 13.06. Notice of Certain Corporate Action. In case:

              (a) the Company shall declare a dividend (or any other
       distribution) on its Common Stock that would require a conversion price
       adjustment pursuant to paragraph (5) of Section 13.04; or

              (b) the Company shall authorize the granting to all holders of its
       Common Stock of rights, warrants or options to subscribe for or purchase
       any shares of capital


<PAGE>   80
                                                                              74


       stock of any class or of any other rights (excluding rights distributed
       pursuant to any shareholder rights plan); or

              (c) of any reclassification of the Common Stock of the Company
       (other than a subdivision or combination of its outstanding shares of
       Common Stock), or of any consolidation or merger to which the Company is
       a party and for which approval of any shareholders of the Company is
       required, or of the sale or transfer of all or substantially all of the
       assets of the Company; or

              (d) of the voluntary or involuntary dissolution, liquidation or
       winding, up of the Company; or

              (e) the Company or any Subsidiary of the Company shall commence a
       tender or exchange offer for all or a portion of the Company's
       outstanding shares of Common Stock (or shall amend any such tender or
       exchange offer);

then the Company shall cause to be filed at each office or agency maintained for
the purpose of conversion of Securities pursuant to Section 10.02, and shall
cause to be mailed to all Holders at their last addresses as they shall appear
in the Security Register, at least 20 days (or 10 days in any case specified in
clause (a) or (b) above) prior to the applicable record, effective or expiration
date hereinafter specified, a notice stating (x) the date on which a record is
to be taken for the purpose of such dividend, distribution or granting of
rights, warrants or options, or, if a record is not to be taken, the date as of
which the holders of Common Stock of record to be entitled to such dividend,
distribution, rights, warrants or options are to be determined, or (y) the date
on which such reclassification, consolidation, merger, sale, transfer,
dissolution, liquidation or winding up is expected to become effective, and the
date as of which it is expected that holders of Common Stock of record shall be
entitled to exchange their shares of Common Stock for securities, cash or other
property deliverable upon such reclassification, consolidation, merger, sale,
transfer, dissolution, liquidation or winding up, or (z) the date on which such
tender offer commenced, the date on which such tender offer is scheduled to
expire unless extended, the consideration offered and the other material terms
thereof (or the material terms of any amendment thereto).

              SECTION 13.07. Company to Reserve Common Stock. The Company shall
at all times reserve and keep available, free from preemptive rights, out of its
authorized but unissued Common Stock, solely for the purpose of effecting the
conversion of Securities, the whole number of shares of Common Stock then
issuable upon the conversion in full of all outstanding Securities.

              SECTION 13.08. Taxes on Conversions. The Company will pay any and
all taxes that may be payable in respect of the issue or delivery of shares of
Common Stock on conversion of Securities pursuant hereto. The Company shall not,
however, be required to pay any tax which may be payable in respect of any
transfer involved in the issue and delivery of shares of Common Stock in a name
other than that of the Holder of the Security or Securities to be converted, and
no such issue or delivery shall be made unless and until the Person requesting
such issue has paid to the Company the amount of any such tax, or has
established to the satisfaction of the Company that such tax has been paid.


<PAGE>   81
                                                                              75


              SECTION 13.09. Covenant as to Common Stock. The Company covenants
that all shares of Common Stock which may be issued upon conversion of
Securities will upon issue be newly issued (and not treasury shares) and be duly
authorized, validly issued, fully paid and nonassessable and, except as provided
in Section 13.08, the Company will pay all taxes, liens and charges with respect
to the issue thereof.

              SECTION 13.10. Cancellation of Converted Securities. All
Securities delivered for conversion shall be delivered to the Trustee to be
cancelled by or at the direction of the Trustee, which shall dispose of the same
as provided in Section 3.09.

              SECTION 13.11. Provisions in Case of Reclassification,
Consolidation, Merger or Sale of Assets. In the event that the Company shall be
a party to any transaction (including without limitation any (i)
recapitalization or reclassification of the Common Stock (other than a change in
par value, or from par value to no par value, or from no par value to par value,
or as a result of a subdivision or combination of the Common Stock), (ii) any
consolidation of the Company with, or merger of the Company into, any other
person. any merger of another person into the Company (other than a merger which
does not result in a reclassification, conversion, exchange or cancellation of
outstanding shares of Common Stock of the Company), (iii) any sale or transfer
of all or substantially all of the assets of the Company, or (iv) any other
transaction) pursuant to which the Common Stock is converted into the right to
receive other securities, cash or other property, then lawful provision shall be
made as part of the terms of such transaction whereby the Holder of each
Security then outstanding shall have the right thereafter to convert such
Security only into (subject to funds being legally available for such purpose
under applicable law at the time of such conversion) the kind and amount of
securities, cash and other property receivable upon such transaction by a holder
of the number of shares of Common Stock into which such Security might have been
converted immediately prior to such transaction. The Company or the person
formed by such consolidation or resulting from such merger or which acquired
such assets or which acquired the Company's shares, as the case may be, shall
execute and deliver to the Trustee a supplemental indenture establishing such
rights. Such supplemental indenture shall provide for adjustments which, for
events subsequent to the effective date of such supplemental indenture, shall be
as nearly equivalent as may be practicable to the adjustments provided for in
this Article. The above provisions of this Section 13.11 shall similarly apply
to successive transactions of the foregoing type.

                                   ARTICLE XIV

                           Right to Require Repurchase

              SECTION 14.01. Right to Require Repurchase. In the event that
there shall occur a Change in Control (as defined in Section 14.06), then each
Holder shall have the right, at such Holder's option, to require the Company,
subject to the provisions of Section 12.03, to purchase all or any designated
part of such Holder's Securities on the date (the "Repurchase Date") fixed by
the Company that is not less than 30 days nor more than 45 days after the date
the Company gives notice of the Change in Control as contemplated in Section
14.02(a) at a price (the "Repurchase Price") equal to 100% of the principal
amount thereof, together with accrued and unpaid interest through the Repurchase
Date. Such right to require the repurchase of Securities shall not continue


<PAGE>   82
                                                                              76


after a discharge of the Company from its obligations with respect to the
Securities in accordance with Article IV. Any requirements for notice, surrender
or delivery of Securities pursuant to this Article XIV shall, with respect to
any Global Security, be subject to any Applicable Procedures.

              SECTION 14.02. Notice, Method of Exercising Repurchase Right. (a)
On or before the 15th day after the Company knows or reasonably should know a
Change in Control has occurred, the Company, or at the written request of the
Company, the Trustee (in the name and at the expense of the Company), shall give
notice of the occurrence of the Change in Control and of the repurchase right
set forth herein arising as a result thereof by first-class mail, postage
prepaid, or by telefacsimile with written acknowledgment of transmittal to each
Holder of the Securities at such Holder's address appearing in the Security
Register. The Company shall also deliver a copy of such notice of a repurchase
right to the Trustee.

              Each notice of a repurchase right shall state:

              (1) the Repurchase Date,

              (2) the date by which the repurchase right must be exercised,

              (3) the Repurchase Price, and

              (4) the instructions a Holder must follow to exercise its
      repurchase right.

              No failure of the Company to give the foregoing notice shall limit
any Holder's right to exercise a repurchase right. The Trustee shall have no
affirmative obligation to determine if there shall have occurred a Change in
Control.

              (b) To exercise a repurchase right, a Holder shall deliver to the
Company (or an agent designated by the Company for such purpose in the notice
referred to in (a) above) and to the Trustee on or before the 30th day after the
date of transmittal of the notice referred to in (a) above (i) written notice of
the Holder's exercise of such right, which notice shall set forth the name of
the Holder, the principal amount of the Security or Securities (or portion of a
Security) to be repurchased, and a statement that an election to exercise the
repurchase right is being made thereby, and (ii) the Security or Securities with
respect to which the repurchase right is being exercised, duly endorsed for
transfer to the Company. Such written notice shall be irrevocable. If the
Repurchase Date falls between any Regular Record Date and the corresponding
succeeding Interest Payment Date, Securities to be repurchased must be
accompanied by payment from the Holder of an amount equal to the interest
thereon which the registered Holder thereof is to receive on such Interest
Payment Date.

              (c) In the event a repurchase right shall be exercised in
accordance with the terms hereof, the Company shall on the Repurchase Date pay
or cause to be paid in cash to the Holder thereof the Repurchase Price of the
Security or Securities as to which the repurchase right had been exercised.

              SECTION 14.03. Deposit of Repurchase Price. On or prior to the
Repurchase Date, the Company shall deposit with the Trustee or with a Paying
Agent (or, if the Company is acting as its own Paying Agent, segregate and hold
in trust as provided


<PAGE>   83
                                                                              77


in Section 10.03) an amount of money sufficient to pay the Repurchase Price of
the Securities which are to be repaid on the Repurchase Date.

              SECTION 14.04. Securities Not Repurchased on Repurchase Date. If
any Security surrendered for repurchase shall not be so paid on the Repurchase
Date, the principal of such Security shall, until paid, bear interest from the
Repurchase Date at a rate borne by such Security.

              SECTION 14.05. Securities Repurchased in Part. Any Security which
is to be repurchased only in part shall be surrendered at any office or agency
of the Company designated for that purpose pursuant to Section 10.02 (with, if
the Company or the Trustee so requires, due endorsement by, or written
instrument of transfer in form satisfactory to the Company and the Trustee duly
executed by, the Holder thereof or his attorney duly authorized in writing), and
the Company shall execute, and the Trustee shall authenticate and deliver to the
Holder of such Security without service charge, a new Security or Securities of
any authorized denomination as requested by such Holder, in aggregate principal
amount equal to and in exchange for the unrepurchased portion of the principal
of the Security so surrendered.

              SECTION 14.06. Certain Definitions. For purposes of this Article:
The term "Beneficial Owner" shall be determined in accordance with Rules 13d-3
and 13d-5 promulgated by the Commission under the Exchange Act, or any successor
provision thereto, except that a Person shall be deemed to have "beneficial
ownership" of all shares that such Person has the right to acquire, whether such
right is exercisable immediately or only after the passage of time.

              A "Change in Control" shall be deemed to have occurred at such
time as (a) any Person, or any Persons acting together in a manner which would
constitute a "group" (a "Group") for purposes of Section 13(d) of the Exchange
Act, or any successor provision thereto, together with any Affiliates thereof,
(i) become the Beneficial Owners, directly or indirectly, of capital stock of
the Company, entitling such Person or Persons and its or their Affiliates to
exercise more than 50% of the total voting power of all classes of the Company's
capital stock entitled to vote generally in the election of directors or (ii)
shall succeed in having sufficient of its or their nominees (who are not
supported by a majority of the then current Board of Directors of the Company)
elected to the Board of Directors of the Company such that such nominees, when
added to any existing directors remaining on the Board of Directors of the
Company after such election who are Affiliates of or acting in concert with any
such Persons, shall constitute a majority of the Board of Directors of the
Company, (b) the Company shall be a party to any transaction pursuant to which
the Common Stock is converted into the right to receive other securities (other
than common stock), cash and/or property (or the Company, by dividend, tender or
exchange offer or otherwise, distributes other securities, cash and/or property
to holders of Common Stock) and the value of all such securities, cash and/or
property distributed in such transaction and any other transaction effected
within the 12 months preceding consummation of such transaction (as determined
in good faith by the Board of Directors, whose determination shall be conclusive
and described in a Board Resolution) is more than 50% of the average of the
daily Closing Prices for the five consecutive Trading Days ending on the Trading
Day immediately preceding the date of such transaction (or, if earlier, the
Trading Day immediately preceding the "ex" date (as defined in paragraph (7) of
Section 13.04) for such transaction) or (c) the Company shall consolidate with
or merge into any other


<PAGE>   84
                                                                              78


Person or sell, convey, transfer or lease its properties and assets
substantially as an entirety to any Person other than a Subsidiary, or any other
Person shall consolidate with or merge into the Company (other than, in the case
of this clause (c), pursuant to any consolidation or merger where Persons who
are shareholders of the Company immediately prior thereto become the Beneficial
Owners of shares of capital stock of the surviving company entitling such
Persons to exercise more than 50% of the total voting power of all classes of
such surviving company's capital stock entitled to vote generally in the
election of directors).

              Notwithstanding the foregoing, a "Change in Control" will be
deemed not to have occurred (i) if the Closing Price of the Common Stock for any
five Trading Days during the ten Trading Days immediately preceding the Change
in Control is at least equal to 105% of the conversion price in effect
immediately preceding the Change in Control or (ii) if at least 90% of the
consideration (excluding cash payments for fractional shares or cash payments
for appraisal rights) received or to be received by the shareholders of the
Company in the transaction or transactions constituting the Change in Control
consists of (x) shares of common stock or securities convertible into such
shares of common stock, of an entity organized and validly existing under the
laws of the United States of America, any State thereof or the District of
Columbia the common stock of which is, or upon issuance will be, traded on a
national securities exchange in the United States of America or through Nasdaq
or (y) shares of common stock of an entity organized and validly existing under
the laws of a jurisdiction outside of the United States of America, or American
Depositary Shares representing such shares of common stock, that are, or upon
issuance will be, traded on a national securities exchange in the United States
of America or through Nasdaq, if such entity has an average worldwide total
market capitalization of its equity securities of at least U.S. $5 billion
during the ten Trading Days immediately preceding the date of the Change in
Control.

                                   ARTICLE XV

                       Defeasance and Covenant Defeasance

              SECTION 15.01. Company's Option to Effect Defeasance or Covenant
Defeasance. The Company may at its option by Board Resolution, at any time,
elect to have either Section 15.02 or Section 15.03 applied to the Outstanding
Securities upon compliance with the conditions set forth below in this Article
XV.

              SECTION 15.02. Defeasance and Discharge. Upon the Company's
exercise of the option provided in Section 15.01 applicable to this Section, the
Company shall be deemed to have been discharged from its obligations with
respect to the Outstanding Securities (other than those specified below), the
Holders and any holders of Senior Indebtedness, and the provisions of Article
XII hereof shall cease to be effective, on the date the conditions set forth
below are satisfied (hereinafter, "defeasance"). For this purpose, such
defeasance means that the Company shall be deemed to have paid and discharged
the entire indebtedness represented by the Outstanding Securities, the Company
shall be deemed to have satisfied all their other obligations under such
Securities and this Indenture insofar as such Securities are concerned (and the
Trustee, at the expense of the Company, shall execute proper instruments
acknowledging the same), except for the following which shall survive until
otherwise terminated or discharged hereunder: (A) the rights of Holders of such
Securities to receive, solely from the trust


<PAGE>   85
                                                                             79


fund described in Section 15.04 and as more fully set forth in such Section,
payments in respect of the principal of, premium, if any and interest on such
Securities when such payments are due, (B) the Company's obligations with
respect to such Securities under Sections 3.04, 3.05, 3.06, 10.02, 10.03, 10.11,
Article XIII and Article XIV, (C) the rights, powers, trusts, duties and
immunities of the Trustee hereunder and (D) this Article XV. Subject to
compliance with this Article XV, the Company may exercise its option under this
Section 15.02 notwithstanding the prior exercise of its option under Section
15.03.

              SECTION 15.03. Covenant Defeasance. Upon the Company's exercise of
the option provided in Section 15.01 applicable to this Section, (i) the Company
shall be released from its obligations under Section 10.06 and Section 10.07,
(ii) the occurrence of an event specified in Section 5.01(4) (with respect to
either of Section 10.06 or Section 10.07) or 5.01(5) shall not be deemed to be
an Event of Default and (iii) the provisions of Article XII hereof shall cease
to be effective on and after the date the conditions set forth below are
satisfied (hereinafter, "covenant defeasance"). For this purpose, such covenant
defeasance means that the Company may omit to comply with and shall have no
liability in respect of any term, condition or limitation set forth in any such
Section or Article, whether directly or indirectly by reason of any reference
elsewhere herein to any such Section or Article or by reason of any reference in
any such Section or Article to any other provision herein or in any other
document, but the remainder of this Indenture and such Securities shall be
unaffected thereby.

              SECTION 15.04. Conditions to Defeasance or Covenant Defeasance.
The following shall be the conditions to application of either Section 15.02 or
Section 15.03 to the then Outstanding Securities:

              (1) The Company shall irrevocably have deposited or caused to be
       deposited with the Trustee (or another trustee satisfying the
       requirements of Section 6.09 who shall agree to comply with the
       provisions of this Article XV applicable to it) as trust funds in trust
       for the purpose of making the following payments, specifically pledged as
       security for, and dedicated solely to, the benefit of the Holders of such
       Securities, (A) money in an amount, or (B) U.S. Government Obligations
       which through the scheduled payment of principal and interest in respect
       thereof in accordance with their terms will provide, not later than one
       day before the due date of any payment, money in an amount, or (C) a
       combination thereof, sufficient, in the written opinion of a nationally
       recognized firm of independent public accountants expressed in a written
       certification thereof delivered to the Trustee, to pay and discharge, and
       which shall be applied by the Trustee (or other qualifying trustee) to
       pay and discharge, the principal of, premium, if any, and each
       installment of interest on the Securities on the Stated Maturity of such
       principal or installment of interest in accordance with the terms of this
       Indenture and of such Securities. For this purpose, "U.S. Government
       Obligations" means securities that are (x) direct obligations of the
       United States of America for the payment of which its full faith and
       credit is pledged or (y) obligations of a Person controlled or supervised
       by and acting as an agency or instrumentality of the United States of
       America the payment of which is unconditionally guaranteed as a full
       faith and credit obligation by the United States of America, which, in
       either case, are not callable or redeemable at the option of the issuer
       thereof, and shall also include a depository receipt issued by a bank (as
       defined in Section 3(a)(2) of the Securities Act) as custodian with
       respect to any such U.S. Government Obligation or a specific


<PAGE>   86
                                                                              80


       payment of principal of or interest on any such U.S. Government
       Obligation held by such custodian for the account of the holder of such
       depository receipt; provided that (except as required by law) such
       custodian is not authorized to make any deduction from the amount payable
       to the holder of such depository receipt from any amount received by the
       custodian in respect of the U.S. Government Obligation or the specific
       payment of principal of or interest on the U.S. Government Obligation
       evidenced by such depository receipt.

              (2) In the case of an election under Section 15.02, the Company
       shall have delivered to the Trustee an Opinion of Counsel stating that
       (x) the Company has received from, or there has been published by, the
       Internal Revenue Service a ruling, or (y) since the date of this
       Indenture there has been a change in the applicable Federal income tax
       law, in either case to the effect that, and based thereon such opinion
       shall confirm that, the Holders of the Outstanding Securities will not
       recognize gain or loss for Federal income tax purposes as a result of
       such deposit, defeasance and discharge and will be subject to Federal
       income tax on the same amount, in the same manner and at the same times
       as would have been the case if such deposit, defeasance and discharge had
       not occurred.

              (3) In the case of an election under Section 15.03, the Company
       shall have delivered to the Trustee an Opinion of Counsel to the effect
       that the Holders of the Outstanding Securities will not recognize gain or
       loss for Federal income tax purposes as a result of such deposit and
       covenant defeasance and will be subject to Federal income tax on the same
       amount, in the same manner and at the same times as would have been the
       case if such deposit and covenant defeasance had not occurred.

              (4) The Company shall have delivered to the Trustee an Officers'
       Certificate to the effect that the Securities, if then listed on any
       securities exchange, will not be delisted as a result of such deposit.

              (5) Such defeasance or covenant defeasance shall not cause the
       Trustee to have a conflicting interest as defined in Section 6.08 and for
       purposes of the Trust Indenture Act with respect to any securities of the
       Company.

              (6) At the time of such deposit: (A) no default in the payment of
       all or a portion of principal of (or premium, if any) or interest on or
       other obligations in respect of any Senior Indebtedness shall have
       occurred and be continuing, and no event of default with respect to any
       Senior Indebtedness shall have occurred and be continuing and shall have
       resulted in such Senior Indebtedness becoming or being declared due and
       payable prior to the date on which it would otherwise have become due and
       payable and (B) no other event with respect to any Senior Indebtedness
       shall have occurred and be continuing permitting (after notice or the
       lapse of time, or both) the holders of such Senior Indebtedness (or a
       trustee on behalf of the holders thereof) to declare such Senior
       Indebtedness due and payable prior to the date on which it would
       otherwise have become due and payable, or, in the case of either clause
       (A) or clause (B) above, each such default or event of default shall have
       been cured or waived or shall have ceased to exist.

              (7) No Event of Default or event which with notice or lapse of
       time or both would become an Event of Default shall have occurred and be
       continuing on


<PAGE>   87
                                                                              81


       the date of such deposit or, insofar as subsections 5.01(6) and (7) are
       concerned, at any time during the period ending on the 121st day after
       the date of such deposit (it being understood that this condition shall
       not be deemed satisfied until the expiration of such period).

              (8) Such defeasance or covenant defeasance shall not result in a
       breach or violation of, or constitute a default under, any other
       agreement or instrument to which the Company is a party or by which it is
       bound.

              (9) The Company shall have delivered to the Trustee an Officers'
       Certificate and an Opinion of Counsel, each stating that all conditions
       precedent provided for relating to either the defeasance under Section
       15.02 or the covenant defeasance under Section 15.03 (as the case may be)
       have been complied with.

              (10) Such defeasance or covenant defeasance shall not result in
       the trust arising from such deposit constituting an investment company as
       defined in the Investment Company Act of 1940, as amended, or such trust
       shall be qualified under such act or exempt from regulation thereunder.

              SECTION 15.05. Deposited Money and U.S. Government Obligations to
Be Held in Trust; Other Miscellaneous Provisions. Subject to the provisions of
the last paragraph of Section 10.03, all money and U.S. Government Obligations
(including the proceeds thereof) deposited with the Trustee (or other qualifying
trustee collectively, for purposes of this Section 15.05, the "Trustee")
pursuant to Section 15.04 in respect of the Securities shall be held in trust
and applied by the Trustee, in accordance with the provisions of such Securities
and this Indenture, to the payment, either directly or through any Paying Agent
(including the Company acting as its own Paying Agent) as the Trustee may
determine, to the Holders of such Securities, of all sums due and to become due
thereon in respect of principal, premium, if any, and interest. Money so held in
trust shall not be subject to the provisions of Article XII.

              The Company shall pay and indemnify the Trustee against any tax,
fee or other charge imposed on or assessed against the U.S. Government
Obligations deposited pursuant to Section 15.04 or the principal and interest
received in respect thereof other than any such tax, fee or other charge which
by law is for the account of the Holders of the Outstanding Securities.

              Anything in this Article XV to the contrary notwithstanding, the
Trustee shall deliver or pay to the Company from time to time upon Company
Request any money or U.S. Government Obligations held by it as provided in
Section 15.04 which, in the opinion of a nationally recognized firm of
independent public accountants expressed in a written certification thereof
delivered to the Trustee, are in excess of the amount thereof which would then
be required to be deposited to effect an equivalent defeasance or covenant
defeasance.

              SECTION 15.06. Reinstatement. If the Trustee or the Paying Agent
is unable to apply any money in accordance with Section 15.02 or 15.03 by reason
of any order or judgment of any court or governmental authority enjoining,
restraining or otherwise prohibiting such application, then the Company's
obligations under this Indenture and the Securities shall be revived and
reinstated as though no deposit had occurred pursuant to this Article XV until
such time as the Trustee or Paying Agent is


<PAGE>   88
                                                                             82


permitted to apply all such money in accordance with Section 15.02 or 15.03;
provided, however, that if the Company makes any payment of principal of,
premium, if any, or interest on any Security following the reinstatement of its
obligations, the Company shall be subrogated to the rights of the Holders of
such Securities to receive such payment from the money held by the Trustee or
the Paying Agent.

                                   ARTICLE XVI

                                    Immunity

              SECTION 16.01. Personal Immunity of Incorporators, Shareholders,
Directors and Officers. No recourse for the payment of the principal of or
interest on the Securities, and no . recourse under or upon any obligation,
covenant or agreement contained in this Indenture or in any indenture
supplemental hereto, or in the Securities, or because of any indebtedness
evidenced thereby, shall be had against any incorporator, or against any past,
present or future shareholder, officer or director, as such, of the Company or
any successor corporation, either directly or through the Company or any
successor corporation, under any rule of law, statute or constitutional
provision or by the enforcement of any assessment or by any legal or equitable
proceeding or otherwise, all such liability being expressly waived and released
by the acceptance of the Securities by the Holders thereof and as part of the
consideration for the issue of the Securities. Each and every Holder of the
Securities, by receiving and holding the same, agrees to the provisions of this
Section 16.01 and waives and releases any and all such recourse, claim and
liability.



<PAGE>   1
EXHIBIT 4.2
- -----------


                               Up to $125,000,000

                           Human Genome Sciences, Inc.

             5-1/2% Convertible Subordinated Notes due July 1, 2006

                          REGISTRATION RIGHTS AGREEMENT

                                                                   June 25, 1999

Credit Suisse First Boston Corporation
Eleven Madison Avenue
New York, New York  10010-3629

Dear Sirs:

              Human Genome Sciences, Inc., a Delaware corporation (the
"Company"), proposes to issue and sell to Credit Suisse First Boston Corporation
("CSFBC"), (the "Initial Purchaser"), upon the terms set forth in a purchase
agreement of even date herewith (the "Purchase Agreement"), $100,000,000
aggregate principal amount (plus up to an additional $25,000,000 principal
amount to cover over-allotments, if any) of 5-1/2% Convertible Subordinated
Notes Due July 1, 2006 (the "Notes") of the Company. The Notes will be
convertible into shares of Common Stock, par value $0.01 per share, of the
Company (the "Common Stock") at the conversion price set forth in the Offering
Circular dated June 22, 1999. The Notes will be issued pursuant to an Indenture,
dated as of June 25, 1999 (the "Indenture"), between the Company and The Bank of
New York (the "Trustee"). As an inducement to the Initial Purchaser to enter
into the Purchase Agreement and in satisfaction of a condition to the Initial
Purchaser's obligations thereunder, the Company agrees with the Initial
Purchaser, (i) for the benefit of the Initial Purchaser and (ii) for the benefit
of the holders of the Notes and the Common Stock issuable upon conversion of the
Notes (collectively, the "Securities") from time to time until such time as such
Securities have been sold pursuant to a Shelf Registration Statement (as defined
below) (each of the foregoing a "Holder" and together the "Holders"), as
follows:

              1. Shelf Registration. The Company shall take the following
actions:

              (a) The Company shall, at its cost, prepare and, as promptly as
practicable (but in no event more than 60 days after so required or requested
pursuant to this Section 1) file with the Securities and Exchange Commission
(the "Commission") and thereafter shall use its best efforts to cause to be
declared


<PAGE>   2
                                                                               2


effective as soon as practicable a registration statement on Form S-3 (the
"Shelf Registration Statement") covering the offer and sale of the Transfer
Restricted Securities (as defined in Section 5 hereof) by the Holders thereof
from time to time in accordance with the methods of distribution set forth in
the Shelf Registration Statement and Rule 415 under the Securities Act of 1933,
as amended (the "Securities Act") (hereinafter, the "Shelf Registration");
provided, however, that no Holder (other than the Initial Purchaser) shall be
entitled to have the Securities held by it covered by such Shelf Registration
Statement unless such Holder agrees in writing to be bound by all the provisions
of this Agreement applicable to such Holder.

              (b) The Company shall use its best efforts to keep the Shelf
Registration Statement continuously effective, in order to permit the prospectus
included therein to be lawfully delivered by the Holders of the relevant
Securities, for a period of two years (or for such longer period if extended
pursuant to Section 2(h) below) from the date of its effectiveness or such
shorter period that will terminate when all the Securities covered by the Shelf
Registration Statement (i) have been sold pursuant thereto or (ii) may be sold
pursuant to Rule 144(k) under the Securities Act (or any successor rule
therefore), assuming for this purpose that the Holders thereof are not
affiliates of the Company (in any such case, such period being called the "Shelf
Registration Period"). The Company shall be deemed not to have used its best
efforts to keep the Shelf Registration Statement effective during the requisite
period if it voluntarily takes any action that would result in Holders of
Securities covered thereby not being able to offer and sell such Securities
during that period, unless (i) such action is required by applicable law or (ii)
upon the occurrence of any event contemplated by paragraph 2(b)(v) below, such
action is taken by the Company in good faith and for valid business reasons and
the Company thereafter complies with the requirements of paragraph 2(h).

              (c) Notwithstanding any other provisions of this Agreement to the
contrary, the Company shall cause the Shelf Registration Statement and the
related prospectus and any amendment or supplement thereto, as of the effective
date of the Shelf Registration Statement, amendment or supplement, (i) to comply
in all material respects with the applicable requirements of the Securities Act
and the rules and regulations of the Commission and (ii) not to contain any
untrue statement of a material fact or omit to state a material fact required to
be stated therein or necessary to make the statements therein, in light of the
circumstances under which they were made, not misleading.


<PAGE>   3
                                                                               3


              2. Registration Procedures. In connection with the Shelf
Registration contemplated by Section 1 hereof the following provisions shall
apply:

              (a) The Company shall (i) furnish to the Initial Purchaser, prior
to the filing thereof with the Commission, a copy of the Shelf Registration
Statement and each amendment thereof and each amendment or supplement, if any,
to the prospectus included therein and, in the event that an Initial Purchaser
(with respect to any portion of an unsold allotment from the original offering)
is participating in the Shelf Registration Statement, shall use its best efforts
to reflect in each such document, when so filed with the Commission, such
comments as the Initial Purchaser reasonably may propose; and (ii) include the
names of the Holders who propose to sell Securities pursuant to the Shelf
Registration Statement, as selling security holders.

              (b) The Company shall give written notice to the Initial Purchaser
and the Holders (which notice pursuant to clauses (ii)-(v) hereof shall be
accompanied by an instruction to suspend the use of the prospectus until the
requisite changes have been made):

              (i) when the Shelf Registration Statement or any amendment thereto
       has been filed with the Commission and when the Shelf Registration
       Statement or any post-effective amendment thereto has become effective;

              (ii) of any request by the Commission for amendments or
       supplements to the Shelf Registration Statement or the prospectus
       included therein or for additional information;

              (iii) of the issuance by the Commission of any stop order
       suspending the effectiveness of the Shelf Registration Statement or the
       initiation of any proceedings for that purpose;

              (iv) of the receipt by the Company or its legal counsel of any
       notification with respect to the suspension of the qualification of the
       Securities for sale in any jurisdiction or the initiation or threatening
       of any proceeding for such purpose; and

              (v) of the happening of any event or circumstance that would
       require the Company to make changes in the Shelf Registration Statement
       or the prospectus in order that the Shelf Registration Statement or the
       prospectus do not contain an untrue statement of a material fact nor omit
       to state a material fact required to be stated therein or necessary to
       make the statements therein (in the case of the

<PAGE>   4
                                                                               4


       prospectus, in light of the circumstances under which they were made) not
       misleading, which written notice need not provide any detail as to the
       nature of such event.

              (c) The Company shall make every reasonable effort to obtain the
withdrawal, at the earliest possible time, of any order suspending the
effectiveness of the Shelf Registration Statement.

              (d) The Company shall furnish to each Holder of Securities
included within the coverage of the Shelf Registration, without charge, at least
one copy of the Shelf Registration Statement and any post-effective amendment
thereto, including financial statements and schedules, and, if the Holder so
requests in writing, all exhibits thereto (including those, if any, incorporated
by reference).

              (e) The Company shall, during the Shelf Registration Period,
deliver to each Holder of Securities included within the coverage of the Shelf
Registration Statement, without charge, as many copies of the prospectus
(including each preliminary prospectus) included in the Shelf Registration
Statement and any amendment or supplement thereto as such person may reasonably
request. The Company consents, subject to the provisions of this Agreement, to
the use of the prospectus or any amendment or supplement thereto by each of the
selling Holders in connection with the offering and sale of the Securities
covered by the prospectus, or any amendment or supplement thereto, included in
the Shelf Registration Statement.

              (f) Prior to any public offering of the Securities, pursuant to
the Shelf Registration Statement, the Company shall register or qualify or
cooperate with the Holders of the Securities included therein and their
respective counsel in connection with the registration or qualification of such
Securities for offer and sale under the securities or "blue sky" laws of such
states of the United States as any such Holder reasonably requests in writing
and do any and all other acts or things necessary or advisable to enable the
offer and sale in such jurisdictions of the Securities covered by the Shelf
Registration Statement; provided, however, that the Company shall not be
required to (i) qualify generally to do business in any jurisdiction where it is
not then so qualified or (ii) take any action which would subject it to general
service of process or to taxation in any jurisdiction where it is not then so
subject.

              (g) The Company shall cooperate with the Holders of the Securities
to facilitate the timely preparation and delivery of certificates representing
the Securities to be sold pursuant to the Shelf Registration Statement free of
any restrictive legends and in such denominations and registered in such names
as


<PAGE>   5
                                                                               5


the Holders may request a reasonable period of time prior to sales of the
Securities pursuant to the Shelf Registration Statement.

              (h) Upon the occurrence of any event contemplated by paragraphs
(ii) through (v) of Section 2(b) above during the period for which the Company
is required to maintain an effective Shelf Registration Statement, the Company
shall, as required hereby, prepare and file a post-effective amendment to the
Shelf Registration Statement or an amendment or supplement to the related
prospectus and any other required document so that, as thereafter delivered to
Holders or purchasers of Securities, the prospectus will not contain an untrue
statement of a material fact or omit to state any material fact required to be
stated therein or necessary to make the statements therein, in light of the
circumstances under which they were made, not misleading. If the Company
notifies the Initial Purchaser and the Holders in accordance with paragraphs
(ii) through (v) of Section 2(b) above to suspend the use of the prospectus
until the requisite changes to the prospectus have been made, then the Initial
Purchaser and the Holders shall suspend use of such prospectus and the period of
effectiveness of the Shelf Registration Statement provided for in Section 1(b)
above shall be extended by the number of days from and including the date of
giving such notice to and including the date when the Initial Purchaser and the
Holders shall have received such amended or supplemented prospectus pursuant to
this Section 2(h). Any such amendment, supplement or document will be prepared
and filed as promptly as practicable under the circumstances, as determined in
good faith by the Company, it being understood that the Company may have bona
fide reasons to delay such preparation and filing for a period which may not in
any event exceed 60 days.

              (i) Not later than the effective date of the Shelf Registration
Statement, the Company will provide CUSIP numbers for the Notes and the Common
Stock registered under the Shelf Registration Statement, and provide the Trustee
with printed certificates for such Notes, in form eligible for deposit with The
Depository Trust Company.

              (j) The Company will comply with all rules and regulations of the
Commission to the extent and so long as they are applicable to the Shelf
Registration and will make generally available to its security holders (or
otherwise provide in accordance with Section 11(a) of the Securities Act) an
earnings statement satisfying the provisions of Section 11(a) of the Securities
Act, no later than 45 days after the end of a 12-month period (or 90 days, if
such period is a fiscal year) beginning with the first month of the Company's
first fiscal quarter commencing after the effective date of the Shelf
Registration Statement, which statement shall cover such 12-month period.


<PAGE>   6
                                                                               6


              (k) The Company shall cause the Indenture to be qualified under
the Trust Indenture Act of 1939, as amended (the "Trust Indenture Act"), in a
timely manner and containing such changes, if any, as shall be necessary for
such qualification. In the event that such qualification would require the
appointment of a new trustee under the Indenture, the Company shall appoint a
new trustee thereunder pursuant to the applicable provisions of the Indenture.

              (l) The Company may require each Holder of Securities to be sold
pursuant to the Shelf Registration Statement to furnish to the Company such
information regarding the Holder and the distribution of the Securities as the
Company may from time to time reasonably require for inclusion in the Shelf
Registration Statement, and the Company may exclude from such registration the
Securities of any Holder that fails to furnish such information within a
reasonable time after receiving such request.

              (m) The Company shall enter into such customary agreements
(including, if requested, an underwriting agreement in customary form) and take
all other actions, if any, as any Holder shall reasonably request in order to
facilitate the disposition of the Securities pursuant to the Shelf Registration,
provided, however, that the Company shall not be required to facilitate an
underwritten offering pursuant to the Shelf Registration Statement by any
Holders unless the offering relates to at least $50,000,000 principal amount of
the Notes or the equivalent number of shares of Common Stock into which such
Notes are convertible.

              (n) The Company shall (i) make reasonably available for inspection
by the Holders of the Securities, any underwriter participating in any
distribution pursuant to the Shelf Registration Statement and any attorney,
accountant or other agent retained by the Holders of the Securities or any such
underwriter all relevant financial and other records, pertinent corporate
documents and properties of the Company and (ii) cause the Company's officers,
directors, employees, accountants and auditors to supply all relevant
information reasonably requested by the Holders of the Securities or any such
underwriter, attorney, accountant or agent in connection with the Shelf
Registration Statement, in each case, as shall be reasonably necessary to enable
such persons, to conduct a reasonable investigation within the meaning of
Section 11 of the Securities Act; provided, however, that the foregoing
inspection and information gathering (i) shall be coordinated on behalf of the
Initial Purchaser by you and on behalf of the other parties, by one counsel
designated by and on behalf of the other parties as described in Section 3
hereof.


<PAGE>   7
                                                                               7


              (o) The Company, if requested by any Holder of Securities covered
by Shelf Registration Statement, shall cause (i) its counsel (which may include
the Company's general counsel for one or more of the opinions) to deliver an
opinion and updates thereof relating to the Securities in customary form
addressed to such Holders, and the managing underwriters, if any, thereof, and
dated, in the case of the initial opinion, the effective date of such Shelf
Registration Statement (it being agreed that the matters to be covered by such
opinion shall include, without limitation, the due incorporation and good
standing of the Company; the qualification of the Company to transact business
as a foreign corporation; the due authorization, execution and delivery of the
relevant agreement of the type referred to in Section 2(m) hereof; the due
authorization, execution, authentication and issuance, and the validity and
enforceability, of the applicable Securities; the absence of material legal or
governmental proceedings involving the Company; the absence of governmental
approvals required to be obtained in connection with the Shelf Registration
Statement, the offering and sale of the applicable Securities, or any agreement
of the type referred to in Section 2(m) hereof; the compliance as to form of
such Shelf Registration Statement and any documents incorporated by reference
therein and of the Indenture with the requirements of the Securities Act and the
Trust Indenture Act, respectively; and, as of the date of the opinion and as of
the effective date of the Shelf Registration Statement or most recent
post-effective amendment thereto, as the case may be, the absence from such
Shelf Registration Statement and the prospectus included therein, as then
amended or supplemented, and from any documents incorporated by reference
therein of an untrue statement of a material fact or the omission to state
therein a material fact required to be stated therein or necessary to make the
statements therein not misleading (in the case of any such documents, in the
light of the circumstances existing at the time that such documents were filed
with the Commission under the Securities Exchange Act of 1934, as amended (the
"Exchange Act")), (ii) its officers to execute and deliver all customary
documents and certificates and updates thereof requested by any underwriters of
the applicable Securities or counsel for the Holders and (iii) its independent
public accountants and the independent public accountants with respect to any
other entity for which financial information is provided in the Shelf
Registration Statement to provide to the selling Holders of the applicable
Securities and any underwriter therefor a comfort letter in customary form and
covering matters of the type customarily covered in comfort letters in
connection with primary underwritten offerings, subject to receipt of
appropriate documentation as contemplated, and only if permitted, by Statement
of Auditing Standards No. 72.


<PAGE>   8
                                                                               8


              (p) The Company shall use its best efforts to take all other steps
necessary to effect the registration of the Securities covered by the Shelf
Registration Statement contemplated hereby.

              3. Registration Expenses. The Company shall bear all fees and
expenses incurred in connection with the performance of its obligations under
Sections 1 through 2 hereof (including the reasonable fees and expenses, if any,
of Cravath, Swaine & Moore, counsel for the Initial Purchaser, incurred in
connection with the Shelf Registration), whether or not the Shelf Registration
Statement is filed or becomes effective, and shall bear or reimburse the Holders
of the Securities covered by the Shelf Registration for the reasonable fees and
disbursements of one firm of counsel designated by the Holders of a majority in
principal amount of the Securities covered by the Shelf Registration Statement
(provided that Holders of Common Stock issued upon the conversion of the Notes
shall be deemed to be Holders of the aggregate principal amount of Notes from
which such Common Stock was converted) to act as counsel for the Holders in
connection therewith.

              4. Indemnification. (a) The Company agrees to indemnify and hold
harmless each Holder and each person, if any, who controls such Holder within
the meaning of the Securities Act or the Exchange Act (each Holder and such
controlling persons are referred to collectively as the "Indemnified Parties")
from and against any losses, claims, damages or liabilities, joint or several,
or any actions in respect thereof (including, but not limited to, any losses,
claims, damages, liabilities or actions relating to purchases and sales of the
Securities) to which each Indemnified Party becomes subject under the Securities
Act, the Exchange Act or otherwise, insofar as such losses, claims, damages,
liabilities or actions arise out of or are based upon any untrue statement or
alleged untrue statement of a material fact contained in the Shelf Registration
Statement or prospectus, including any document incorporated by reference
therein, or in any amendment or supplement thereto or in any preliminary
prospectus relating to the Shelf Registration, or arise out of, or are based
upon, the omission or alleged omission to state therein a material fact required
to be stated therein or necessary to make the statements therein not misleading,
and shall reimburse, as incurred, the Indemnified Parties for any legal or other
expenses reasonably incurred by them in connection with investigating or
defending any such loss, claim, damage, liability or action in respect thereof;
provided, however, that (i) the Company shall not be liable in any such case to
the extent that such loss, claim, damage or liability arises out of or is based
upon any untrue statement or alleged untrue statement or omission or alleged
omission made in the Shelf Registration Statement or prospectus or in any
amendment or supplement thereto


<PAGE>   9
                                                                               9


or in any preliminary prospectus relating to the Shelf Registration in reliance
upon and in conformity with written information pertaining to such Holder and
furnished to the Company by or on behalf of such Holder specifically for
inclusion therein and (ii) with respect to any untrue statement or omission or
alleged untrue statement or omission made in any preliminary prospectus relating
to the Shelf Registration Statement, the indemnity agreement contained in this
subsection (a) shall not inure to the benefit of any Holder from whom the person
asserting any such losses, claims, damages or liabilities purchased the
Securities concerned, to the extent that a prospectus relating to such
Securities was required to be delivered by such Holder under the Securities Act
in connection with such purchase and any such loss, claim, damage or liability
of such Holder results from the fact that there was not sent or given to such
person, at or prior to the written confirmation of the sale of such Securities
to such person, a copy of the final prospectus if the Company had previously
furnished copies thereof to such Holder; provided further, however, that this
indemnity agreement will be in addition to any liability which the Company may
otherwise have to such Indemnified Party.

              The Company shall also indemnify the underwriters, their officers
and directors and each person who controls such underwriters within the meaning
of the Securities Act or the Exchange Act to the same extent as provided above
with respect to the indemnification of the Holders if requested by such Holders.

              (b) Each Holder, severally and not jointly, will indemnify and
hold harmless the Company, its officers and directors and each person, if any,
who controls the Company within the meaning of the Securities Act or the
Exchange Act from and against any losses, claims, damages or liabilities or any
actions in respect thereof, to which the Company or any such controlling person
may become subject under the Securities Act, the Exchange Act or otherwise,
insofar as such losses, claims, damages, liabilities or actions arise out of or
are based upon any untrue statement or alleged untrue statement of a material
fact contained in a Shelf Registration Statement or prospectus or in any
amendment or supplement thereto or in any preliminary prospectus relating to a
Shelf Registration, or arise out of or are based upon the omission or alleged
omission to state therein a material fact necessary to make the statements
therein not misleading, but in each case only to the extent that the untrue
statement or omission or alleged untrue statement or omission was made in
reliance upon and in conformity with written information pertaining to such
Holder and furnished to the Company by or on behalf of such Holder specifically
for inclusion therein; and, subject to the limitation set forth immediately
preceding this clause, shall reimburse, as incurred, the Company for any legal
or other expenses reasonably incurred by the Company or any such


<PAGE>   10
                                                                              10


controlling person in connection with investigating or defending any loss,
claim, damage, liability or action in respect thereof. This indemnity agreement
will be in addition to any liability which such Holder may otherwise have to the
Company or any of its controlling persons.

              (c) Promptly after receipt by an indemnified party under this
Section 4 of notice of the commencement of any action or proceeding (including a
governmental investigation), such indemnified party will, if a claim in respect
thereof is to be made against the indemnifying party under this Section 4,
notify the indemnifying party of the commencement thereof; but the omission so
to notify the indemnifying party will not, in any event, relieve the
indemnifying party from any obligations to any indemnified party other than the
indemnification obligation provided in subsections (a) or (b) above. In case any
such action is brought against any indemnified party, and it notifies the
indemnifying party of the commencement thereof, the indemnifying party will be
entitled to participate therein and, to the extent that it may wish, jointly
with any other indemnifying party similarly notified, to assume the defense
thereof, with counsel reasonably satisfactory to such indemnified party (who
shall not, except with the consent of the indemnified party, be counsel to the
indemnifying party), and after notice from the indemnifying party to such
indemnified party of its election so to assume the defense thereof the
indemnifying party will not be liable to such indemnified party under this
Section 4 for any legal or other expenses, other than reasonable costs of
investigation, subsequently incurred by such indemnified party in connection
with the defense thereof. No indemnifying party shall, without the prior written
consent of the indemnified party, effect any settlement of any pending or
threatened action in respect of which any indemnified party is or could have
been a party and indemnity could have been sought hereunder by such indemnified
party unless such settlement includes an unconditional release of such
indemnified party from all liability on any claims that are the subject matter
of such action.

              (d) If the indemnification provided for in this Section 4 is
unavailable or insufficient to hold harmless an indemnified party under
subsections (a) or (b) above, then each indemnifying party shall contribute to
the amount paid or payable by such indemnified party as a result of the losses,
claims, damages or liabilities (or actions in respect thereof) referred to in
subsections (a) or (b) above (i) in such proportion as is appropriate to reflect
the relative benefits received by the indemnifying party or parties on the one
hand and the indemnified party on the other from the registration of the
Securities, pursuant to the Shelf Registration, or (ii) if the allocation
provided by the foregoing clause (i) is not permitted by


<PAGE>   11
                                                                              11


applicable law, in such proportion as is appropriate to reflect not only the
relative benefits referred to in clause (i) above but also the relative fault of
the indemnifying party or parties on the one hand and the indemnified party on
the other in connection with the statements or omissions that resulted in such
losses, claims, damages or liabilities (or actions in respect thereof) as well
as any other relevant equitable considerations. The relative fault of the
parties shall be determined by reference to, among other things, whether the
untrue or alleged untrue statement of a material fact or the omission or alleged
omission to state a material fact relates to information supplied by the Company
on the one hand or such Holder or such other indemnified party, as the case may
be, on the other, and the parties' relative intent, knowledge, access to
information and opportunity to correct or prevent such statement or omission.
The amount paid by an indemnified party as a result of the losses, claims,
damages or liabilities referred to in the first sentence of this subsection (d)
shall be deemed to include any legal or other expenses reasonably incurred by
such indemnified party in connection with investigating or defending any action
or claim which is the subject of this subsection (d). Notwithstanding any other
provision of this Section 4(d), the Holders shall not be required to contribute
any amount in excess of the amount by which the net proceeds received by such
Holders from the sale of the Securities pursuant to the Shelf Registration
Statement exceeds the amount of damages which such Holders have otherwise been
required to pay by reason of such untrue or alleged untrue statement or omission
or alleged omission. No person guilty of fraudulent misrepresentation (within
the meaning of Section 11(f) of the Securities Act) shall be entitled to
contribution from any person who was not guilty of such fraudulent
misrepresentation. For purposes of this paragraph (d), each person, if any, who
controls such indemnified party within the meaning of the Securities Act or the
Exchange Act shall have the same rights to contribution as such indemnified
party and each person, if any, who controls the Company within the meaning of
the Securities Act or the Exchange Act shall have the same rights to
contribution as the Company.

              (e) The agreements contained in this Section 4 shall survive the
sale of the Securities pursuant to the Shelf Registration Statement and shall
remain in full force and effect, regardless of any termination or cancellation
of this Agreement or any investigation made by or on behalf of any indemnified
party.

              5. Additional Interest Under Certain Circumstances. (a) Additional
interest (the "Additional Interest") with respect to the Notes shall be assessed
as follows if any of the following events occur (each such event in clauses (i)
through (iii) below being herein called a "Registration Default"):


<PAGE>   12
                                                                              12


              (i) if on or prior to the 60th day after the first date of
       original issuance of the Notes, the Shelf Registration Statement has not
       been filed with the Commission;

              (ii) if on or prior to the 120th day after the first date of
       original issuance of the Notes, the Shelf Registration Statement has not
       been declared effective by the Commission; or

              (iii) if after the Shelf Registration Statement is declared
       effective (A) the Shelf Registration Statement thereafter ceases to be
       effective; or (B) the Shelf Registration Statement or the related
       prospectus ceases to be usable in connection with resales of Transfer
       Restricted Securities (as defined below) during the periods specified
       herein because either (1) any event occurs as a result of which the
       related prospectus forming part of such Shelf Registration Statement
       would include any untrue statement of a material fact or omit to state
       any material fact necessary to make the statements therein in the light
       of the circumstances under which they were made not misleading, or (2) it
       shall be necessary to amend such Shelf Registration Statement or
       supplement the related prospectus, to comply with the Securities Act or
       the Exchange Act or the respective rules thereunder.

              Additional Interest shall accrue on the Notes over and above the
interest set forth in the title of the Notes from and including the date on
which any such Registration Default shall occur, to but excluding the date on
which all such Registration Defaults have been cured, at a rate of 0.50% per
annum.

              (b) A Registration Default referred to in Section 5(a)(iii)(B)
shall be deemed not to have occurred and be continuing in relation to the Shelf
Registration Statement or the related prospectus if (i) such Registration
Default has occurred solely as a result of (x) the filing of a post-effective
amendment to the Shelf Registration Statement to incorporate annual audited
financial information with respect to the Company where such post-effective
amendment is not yet effective and needs to be declared effective to permit
Holders to use the related prospectus or (y) other material events, with respect
to the Company that would need to be described in the Shelf Registration
Statement or the related prospectus and (ii) in the case of clause (y), the
Company is proceeding in good faith to amend or supplement the Shelf
Registration Statement and related prospectus to describe such events as
required by paragraph 2(h) hereof; provided, however, that in any case if such
Registration Default occurs for a continuous period in excess of 60 days,
Additional Interest shall be payable in accordance with the above


<PAGE>   13
                                                                              13


paragraph from the day such Registration Default occurs until such Registration
Default is cured.

              (c) Any amounts of Additional Interest due pursuant to clause
(a)(i), (a)(ii) or (a)(iii) of this Section 5 will be payable in cash on the
regular interest payment dates with respect to the Notes. The amount of
Additional Interest will be determined by multiplying the applicable Additional
Interest rate by the principal amount of the Notes, multiplied by a fraction,
the numerator of which is the number of days such Additional Interest rate was
applicable during such period (determined on the basis of a 360-day year
comprised of twelve 30-day months), and the denominator of which is 360. The
indebtedness represented by the Additional Interest shall be subordinated in
right of payment to all existing and future Senior Indebtedness (as defined in
the Indenture) as and to the same extent as the Notes.

              (d) "Transfer Restricted Securities" means each Security until (i)
the date on which such Security has been effectively registered under the
Securities Act and disposed of in accordance with the Shelf Registration
Statement or (ii) the date on which such Security is distributed to the public
pursuant to Rule 144 under the Securities Act or is saleable pursuant to Rule
144(k) under the Securities Act.

              6. Rules 144 and 144A. The Company shall use its best efforts to
file the reports required to be filed by it under the Securities Act and the
Exchange Act in a timely manner and, if at any time the Company is not required
to file such reports, it will, upon the request of any Holder, make publicly
available other information so long as necessary to permit sales of their
securities pursuant to Rules 144 and 144A. The Company covenants that it will
take such further action as any Holder of Securities may reasonably request, all
to the extent required from time to time to enable such Holder to sell Transfer
Restricted Securities without registration under the Securities Act within the
limitations of the exemptions provided by Rules 144 and 144A (including the
requirements of Rule 144A(d)(4)). The Company will provide a copy of this
Agreement to prospective purchasers of Securities identified to the Company by
the Initial Purchaser upon request. Upon the request of any Holder, the Company
shall deliver to such Holder a written statement as to whether it has complied
with such requirements. Notwithstanding the foregoing, nothing in this Section 6
shall be deemed to require the Company to register any of its securities
pursuant to the Exchange Act.

              7. Underwritten Registrations. If any of the Transfer Restricted
Securities covered by the Shelf Registration are to be sold in an underwritten
offering, the investment banker or investment bankers and manager or managers
that will administer


<PAGE>   14
                                                                              14


the offering ("Managing Underwriters") will be selected by the Holders of a
majority in aggregate principal amount of such Transfer Restricted Securities to
be included in such offering (provided that Holders of Common Stock issued upon
conversion of Notes shall not be deemed Holders of Common Stock, but shall be
deemed to be Holders of the aggregate principal amount of Notes from which such
Common Stock was converted).

              No person may participate in any underwritten registration
hereunder unless such person (i) agrees to sell such person's Transfer
Restricted Securities on the basis reasonably provided in any underwriting
arrangements approved by the persons entitled hereunder to approve such
arrangements and (ii) completes and executes all questionnaires, powers of
attorney, indemnities, underwriting agreements and other documents reasonably
required under the terms of such underwriting arrangements.

              8. Miscellaneous. (a) Amendments and Waivers. The provisions of
this Agreement may not be amended, modified or supplemented, and waivers or
consents to departures from the provisions hereof may not be given, except by
the Company and the written consent of the Holders of a majority in principal
amount of the Securities (provided that Holders of Common Stock issued upon
conversion of Notes shall not be deemed Holders of Common Stock, but shall be
deemed to be Holders of the aggregate principal amount of Notes from which such
Common Stock was converted) affected by such amendment, modification,
supplement, waiver or consents.

              (b) Notices. All notices and other communications provided for or
permitted hereunder shall be made in writing by hand delivery, first-class mail,
facsimile transmission, or air courier which guarantees overnight delivery:

              (1) if to a Holder, at the most current address given by such
       Holder to the Company;

              (2) if to the Initial Purchaser, at its address as follows:

                   Credit Suisse First Boston Corporation
                   Eleven Madison Avenue
                   New York, NY 10010-3629
                   Fax No.:  (212) 325-8278
                   Attention:  Transactions Advisory Group


<PAGE>   15
                                                                              15


            with a copy to:

                      Cravath, Swaine & Moore
                      Worldwide Plaza
                      825 Eighth Avenue
                      New York, NY 10019
                      Fax No.:  (212) 474-3700
                      Attention:  Robert Rosenman, Esq.

                 (3) if to the Company, at its address as follows:

                      Human Genome Sciences, Inc.
                      9410 Key West Avenue
                      Rockville, MD 20850
                      Fax No.:  (301) 309-8439
                      Attention:  James H. Davis, Esq.

            with a copy to:

                      Piper & Marbury L.L.P.
                      36 South Charles Street
                      Baltimore, Maryland 21201
                      Fax No.:  (410) 539-0489
                      Attention:  R. W. Smith, Jr., Esq.

              All such notices and communications shall be deemed to have been
duly given: at the time delivered by hand, if personally delivered; three
business days after being deposited in the mail, postage prepaid, if mailed;
when receipt is acknowledged by recipient's facsimile machine operator, if sent
by facsimile transmission; and on the day delivered, if sent by overnight air
courier guaranteeing next day delivery.

              (c) No Inconsistent Agreements. The Company has not, as of the
date hereof, entered into, nor shall it, on or after the date hereof, without
the prior consent of CSFBC, enter into, any agreement with respect to its
securities that is inconsistent with the rights granted to the Holders herein or
otherwise conflicts with the provisions hereof.

              (d) Successors and Assigns. This Agreement shall be binding upon
the Company and its successors and assigns.

              (e) Counterparts. This Agreement may be executed in any number of
counterparts and by the parties hereto in separate counterparts, each of which
when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement.


<PAGE>   16
                                                                              16


              (f) Headings. The headings in this Agreement are for convenience
of reference only and shall not limit or otherwise affect the meaning hereof.

              (g) Governing Law. THIS AGREEMENT SHALL BE GOVERNED BY, AND
CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK WITHOUT REGARD
TO PRINCIPLES OF CONFLICTS OF LAWS.

              By the execution and delivery of this Agreement, the Company
submits to the nonexclusive jurisdiction of any federal or state court in the
State of New York.

              (h) Severability. If any one or more of the provisions contained
herein, or the application thereof in any circumstance, is held invalid, illegal
or unenforceable, the validity, legality and enforceability of any such
provision in every other respect and of the remaining provisions contained
herein shall not be affected or impaired thereby.

              (i) Securities Held by the Company. Whenever the consent or
approval of Holders of a specified percentage of principal amount of Securities
is required hereunder, Securities held by the Company or its affiliates (other
than subsequent Holders of Securities if such subsequent Holders are deemed to
be affiliates solely by reason of their holdings of such Securities)




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