Document:

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                                                                   EXHIBIT 4.14

                                FIRST SUPPLEMENT

                                       to

                          JUNIOR SUBORDINATED INDENTURE

                                      among

                        AMERICAN MUTUAL HOLDING COMPANY,

                           AMERUS LIFE HOLDINGS, INC.

                                       and

                      WILMINGTON TRUST COMPANY, as Trustee

                          Date as of September 20, 2000

<PAGE>   2

                          FIRST SUPPLEMENTAL INDENTURE

     This FIRST SUPPLEMENTAL INDENTURE (this "First Supplemental Indenture") is
made as of the 20th day of September, 2000, among AMERICAN MUTUAL HOLDING
COMPANY, an Iowa mutual insurance holding company ("AMHC"), AMERUS LIFE
HOLDINGS, INC., an Iowa insurance holding company (the "Company"), and
WILMINGTON TRUST COMPANY, as Trustee (the "Trustee").

                                   WITNESSETH:

     WHEREAS, the Company and the Trustee executed and delivered an Indenture,
dated as of February 3, 1997 (the "Indenture"), providing for the issuance by
the Company of unsecured 8.85% junior subordinated debentures, series A;

     WHEREAS, AMHC has executed a Plan of Conversion, dated as of December 17,
1999, pursuant to which AMHC will convert from a mutual insurance holding
company into a stock holding company;

     WHEREAS, the Company and AMHC have executed and delivered an Agreement and
Plan of Merger, dated December 17, 1999, pursuant to which the Company will
merge with and into AMHC, with AMHC as the surviving company (the "Merger");

     WHEREAS, AMHC desires to assume the obligations of the Company under the
Indenture;

     WHEREAS, this First Supplemental Indenture is being executed pursuant to
the requirements of Article Eight of the Indenture, as authorized by Article
Nine of the Indenture and without the consent of the Holders;

     WHEREAS, the execution and delivery by the Company of this Supplemental
Indenture have been duly authorized by Board Resolution and all other action
required to make this First Supplemental Indenture a valid and binding
instrument has been duly taken and performed; and

     WHEREAS, concurrently with the execution and delivery of this First
Supplemental Indenture, the Company is delivering to the Trustee an Officers'
Certificate and an Opinion of Counsel, each stating that the Merger and this
First Supplemental Indenture complies with Article Eight and that all conditions
precedent to the consummation of the Merger under this Indenture have been met.

     NOW, THEREFORE, the parties agree as follows:

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                                   ARTICLE ONE
                                   ASSUMPTION

     SECTION 101. AMHC hereby assumes the due and punctual payment of the
principal of (and premium, if any) and interest (including any Additional
Interest) on all the Securities and the performance or observance of every
covenant of this Indenture and the Securities on the part of the Company to be
performed or observed.

                                   ARTICLE TWO
                                  MISCELLANEOUS

     SECTION 201. Definitions. For all purposes of this First Supplemental
Indenture, except as otherwise herein expressly provided, the definitions, terms
and expressions used herein shall have the same meanings as corresponding
definitions, terms and expressions used in the Indenture.

     SECTION 202. Continuance of Indenture. This First Supplemental Indenture
supplements the Indenture and shall be a part of and subject to all the terms
thereof. The Indenture, as supplemented and amended by this First Supplemental
Indenture, is in all respects ratified and confirmed, and the Indenture and this
First Supplemental Indenture shall be read, taken and construed as one and the
same instrument.

     SECTION 203. Concerning the Trustee. The Trustee accepts the amendment of
the Indenture effected by this First Supplemental Indenture and agrees to
execute the trust created by the Indenture, as hereby amended, but only upon the
terms and conditions set forth in the Indenture, as hereby amended, including
the terms and provisions defining and limiting the liabilities and
responsibilities of the Trustee, which terms and provisions shall in like manner
define and limit its liabilities in the performance of the trust created by the
Indenture, as hereby amended.

     SECTION 204. Governing Law. This First Supplemental Indenture shall be
governed by and construed in accordance with the laws of the State of New York
without regard to the principles of conflicts of laws.

     SECTION 2.05. Counterparts. This First Supplemental Indenture may be
executed in any number of counterparts, each of which when so executed shall be
deemed to be an original, and all of such counterparts shall together constitute
one and the same instrument.

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     IN WITNESS WHEREOF, the parties hereto have caused this Indenture to be
duly executed, and their respective corporate seals to be hereunto affixed and
attested, all as of the day and year first written above.

                                            AMERICAN MUTUAL HOLDING COMPANY

                                            By: /s/ Roger K. Brooks
                                                -------------------------------
                                                Name:  Roger K. Brooks
                                                Title: Chairman, President and
                                                       Chief Executive Officer

Attest:

/s/ James A. Smallenberger
--------------------------
Name:  James A. Smallenberger
Title: Senior Vice President and Secretary

                                            AMERUS LIFE HOLDINGS, INC.

                                            By: /s/ Roger K. Brooks
                                                -------------------------------
                                                Name:  Roger K. Brooks
                                                Title: Chairman, President and
                                                       Chief Executive Officer

Attest:

/s/ James A. Smallenberger
--------------------------
Name:  James A. Smallenberger
Title: Senior Vice President and Secretary

                                            WILMINGTON TRUST COMPANY

                                            By: /s/ Roseline K. Mancy
                                                -------------------------------
                                                Name:  Roseline K. Mancy
                                                Title: Assistant Vice President

Attest:

-----------------------------------
Name:
Title:<PAGE>   1
                                                                   EXHIBIT 4.15

                       ASSIGNMENT AND ASSUMPTION AGREEMENT

                                       to

                      AMENDED AND RESTATED TRUST AGREEMENT

                                     between

                         AMERICAN MUTUAL HOLDING COMPANY

                                       and

                           AMERUS LIFE HOLDINGS, INC.

                            Dated September 20, 2000

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                       ASSIGNMENT AND ASSUMPTION AGREEMENT

     This ASSIGNMENT AND ASSUMPTION AGREEMENT ("Agreement"), dated the 20th day
of September, 2000, is entered into by and between AMERICAN MUTUAL HOLDING
COMPANY, an Iowa mutual insurance holding company ("AMHC") and AMERUS LIFE
HOLDINGS, INC., an Iowa insurance holding company, ("AmerUs"). Capitalized terms
used herein without definition shall have the meanings assigned to such terms in
the Trust Agreement (as defined below).

                                   WITNESSETH:

     WHEREAS, AmerUs and Wilmington Trust Company, a banking corporation duly
organized and existing under the laws of Delaware, as trustee (the "Property
Trustee"), entered into a Trust Agreement, dated as of October 4, 1996 (the
"Original Trust Agreement"), to establish a business trust pursuant to the
Delaware Business Trust Act;

     WHEREAS, AmerUs, the Property Trustee, the Administrative Trustees named
therein, and several Holders as defined therein entered into an Amended and
Restated Trust Agreement (the "Trust Agreement"), dated as of February 3, 1997,
to provide for, among other provisions, the issuance and sale of the Capital
Securities by the Trust pursuant to the Underwriting Agreement;

     WHEREAS, AMHC has executed a Plan of Conversion, dated as of December 17,
1999, pursuant to which AMHC will convert from a mutual insurance holding
company into a stock holding company;

     WHEREAS, AMHC and AmerUs have entered into an Agreement and Plan of Merger,
dated December 17, 1999, pursuant to which the Depositor will merge with and
into AMHC, with AMHC as the surviving company (the "Merger");

     WHEREAS, AmerUs desires to assign and transfer its rights and obligations
under the Trust Agreement to AMHC;

     WHEREAS, AMHC desires to accept and acquire the rights and obligations of
AmerUs under the Trust Agreement;

     WHEREAS, this Assumption Agreement is being executed pursuant to Section
10.07 of the Trust Agreement; and

     WHEREAS, as required by Section 10.07 of the Trust Agreement, the Merger is
permitted under Article Eight of the Indenture.

     NOW, THEREFORE, the parties agree as follows:

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1.   Assignment. Upon the execution of this Agreement by the parties hereto,
     AmerUs does hereby assign and transfer to AMHC all of AmerUs' rights and
     obligations under the Trust Agreement.

2.   Assumption. Upon the execution of this Agreement by the parties hereto,
     AMHC does hereby absolutely and irrevocably accept the foregoing assignment
     and hereby assumes to be solely responsible for and to perform, as
     successor, AmerUs' obligations under the Trust Agreement.

3.   Effectiveness. This Agreement shall become effective as of the Effective
     Time (as defined in the Agreement and Plan of Merger referred to above) of
     the Merger.

4.   Binding Effect; Assigns. This Agreement shall be binding upon, and shall
     enure to the benefit of, the parties hereto and their respective successors
     and assigns.

5.   Execution in Counterparts. This Agreement may be executed in two or more
     counterparts, each of which will be deemed to be an original, but all of
     which together will constitute one and the same agreement.

6.   Governing Law. This Agreement will be governed by and interpreted in
     accordance with the internal laws of the State of New York, without giving
     effect to principles of conflicts of laws.

     IN WITNESS WHEREOF, the parties hereto have executed and delivered this
Agreement as of the date set forth above.

                                            AMERICAN MUTUAL HOLDING COMPANY

                                            By: /s/ Roger K. Brooks
                                                -------------------------------
                                                Name:  Roger K. Brooks
                                                Title: Chairman, President and
                                                       Chief Executive Officer

                                            AMERUS LIFE HOLDINGS, INC.

                                            By: /s/ Roger K. Brooks
                                                -------------------------------
                                                Name:  Roger K. Brooks
                                                Title: Chairman, President and
                                                       Chief Executive Officer

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