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                                                                    Exhibit 4.12

                         UNION ELECTRIC CAPITAL TRUST I
                                 TRUST AGREEMENT

      THIS TRUST AGREEMENT, dated as of June 17, 2002, is by and among (i)
Union Electric Company, a Missouri corporation (the "Depositor"), (ii) The Bank
of New York (Delaware), a Delaware banking corporation, as Delaware trustee (the
"Trustee"), and (iii) Jerre E. Birdsong, as administrator (the "Administrator").
The Depositor, the Trustee and the Administrator hereby agree as follows:

      1. The trust created hereby (the "Trust") shall be known as "Union
Electric Capital Trust I".

      2. The Depositor hereby assigns, transfers, conveys and sets over to the
Trust the sum of $10. Such amount shall constitute the initial trust estate. The
Trustee hereby declares that it will hold the trust estate for the Depositor
subject to the terms hereof.

      3. It is the intention of the parties hereto that the Trust created
hereby constitutes a business trust under Chapter 38 of Title 12 of the
Delaware Code, 12 Del. C. Sections 3801 et seq. (the "Business Trust Act"),
and that this document constitutes the governing instrument of the Trust.

      4. The Trustee is hereby authorized and directed to execute and file a
certificate of trust with the Delaware Secretary of State in accordance with the
provisions of the Business Trust Act.

      5. The Depositor, the Trustee, the Administrator and others will enter
into an amended and restated Trust Agreement, satisfactory to each such party
and substantially in the form to be included as an exhibit to the Registration
Statement on Form S-3 (the "1933 Act Registration Statement") referred to below,
or in such other form as the Depositor, the Trustee, the Administrator and the
other parties thereto may approve, to provide for the contemplated operation of
the Trust created hereby and the issuance of Trust Preferred Securities and
Trust Common Securities referred to therein. Prior to the execution and delivery
of such amended and restated Trust Agreement, the Trustee and the Administrator
shall not have any duty or obligation hereunder or with respect to the trust
estate, except as otherwise required by applicable law or as may be necessary to
obtain, prior to such execution and delivery, any licenses, consents or
approvals required by applicable law or otherwise. Notwithstanding the
foregoing, the Trustee and the Administrator may take all actions deemed proper
as are necessary to effect the transactions contemplated herein.

      6. The Depositor, the Trustee and the Administrator hereby authorize and
direct the Depositor, as the sponsor of the Trust, (i) to file with the
Securities and Exchange Commission (the "Commission") and to execute, in the
case of the 1933 Act Registration Statement and 1934 Act Registration Statement
(as herein defined), on behalf of the Trust, (a) the 1933 Act Registration
Statement, including pre-effective or post-effective amendments to such
Registration Statement, relating to the registration under the Securities Act of
1933, as amended (the "1933 Act"), of the Trust Preferred Securities of the
Trust, (b) any preliminary prospectus or prospectus or supplement thereto
relating to the Trust Preferred Securities required to be filed pursuant to Rule
424 under the 1933 Act, and (c) a Registration Statement on Form 8-A or other


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appropriate form (the "1934 Act Registration Statement") (including all
pre-effective and post-effective amendments thereto) relating to the
registration of the Trust Preferred Securities of the Trust under Section
12(b) of the Securities Exchange Act of 1934, as amended; (ii) to file with
any national securities exchange and execute on behalf of the Trust a listing
application and all other applications, statements, certificates, agreements
and other instruments as shall be necessary or desirable to cause the Trust
Preferred Securities to be listed on such exchange; (iii) to file and execute
on behalf of the Trust such applications, reports, surety bonds, irrevocable
consents, appointments of attorney for service of process and other papers
and documents as shall be necessary or desirable to register the Trust
Preferred Securities under the securities or "Blue Sky" laws of such
jurisdictions as the Depositor, on behalf of the Trust, may deem necessary or
desirable; (iv) to execute, deliver and perform letters or documents to, or
instruments for filing with, a depository relating to the Trust Preferred
Securities; and (v) to execute, deliver and perform on behalf of the Trust,
an underwriting agreement with the Depositor and the underwriter or
underwriters of the Trust Preferred Securities of the Trust. In the event
that any filing referred to in clauses (i) through (iii) above is required by
the rules and regulations of the Commission, any national securities exchange
or state securities or Blue Sky laws to be executed on behalf of the Trust by
the Trustee or the Administrator, the Trustee, in its capacity as a trustee
of the Trust, and the Administrator, in its capacity as an administrator of
the Trust, are hereby authorized and directed to join in any such filing and
to execute on behalf of the Trust any and all of the foregoing, it being
understood that the Trustee, in its capacity as trustee of the Trust, shall
not be required to join in any such filing or execute on behalf of the Trust
any such document unless required by the rules and regulations of the
Commission, any national securities exchange or state securities or Blue Sky
laws. In connection with all of the foregoing, the Trustee, solely in its
capacity as trustee of the Trust, and the Depositor hereby constitute and
appoint Jerre E. Birdsong as its true and lawful attorney-in-fact and agent,
with full power of substitution and resubstitution for the Depositor or in
the Depositor's name, place and stead, in any and all capacities, to sign any
and all amendments (including all pre-effective and post-effective
amendments) to the 1933 Act Registration Statement and the 1934 Act
Registration Statement and to file the same, with all exhibits thereto, and
any other documents in connection therewith, with the Commission, granting
unto said attorney-in-fact and agent full power and authority to do and
perform each and every act and thing requisite and necessary to be done in
connection therewith, as fully to all intents and purposes as the Depositor
might or could do in person, hereby ratifying and confirming all that said
attorney-in-fact and agent or his respective substitute or substitutes, shall
do or cause to be done by virtue hereof.

      7. This Trust Agreement may be executed in one or more counterparts.

      8. The number of trustees initially shall be one (1) and thereafter the
number of trustees shall be such number as shall be fixed from time to time by a
written instrument signed by the Depositor, who may increase or decrease the
number of trustees; provided, however, that, to the extent required by the
Business Trust Act, one trustee shall either be a natural person who is a
resident of Delaware or, if not a natural person, an entity which has its
principal place of business in the State of Delaware and otherwise meets the
requirements of applicable Delaware law. Subject to the foregoing, the Depositor
is entitled to appoint or remove without cause any trustee at any time. Any
trustee may resign upon thirty (30) days' prior written notice to the Depositor.


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      9. The Bank of New York (Delaware), in its capacity as trustee of the
Trust, shall be a trustee of the Trust for the sole purpose of satisfying the
requirements of Section 3807(a) of the Business Trust Act.

      10. The Depositor hereby agrees, to the fullest extent permitted by
applicable law, to (i) reimburse the Trustee and the Administrator for all
reasonable expenses (including reasonable fees and expenses of counsel and other
experts) and (ii) indemnify, defend and hold harmless the Trustee and the
Administrator and any of the officers, directors, employees and agents of the
Trustee or the Administrator (the "Indemnified Persons") from and against any
and all losses, damages, liabilities, claims, actions, suits, costs, expenses,
disbursements (including the reasonable fees and expenses of counsel), taxes and
penalties of any kind and nature whatsoever (collectively, "Expenses"), to the
extent that such Expenses arise out of or are imposed upon or asserted at any
time against such Indemnified Persons with respect to the performance of this
Trust Agreement, the creation, operation or termination of the Trust or the
transactions contemplated hereby; provided, however, that the Depositor shall
not be required to indemnify any Indemnified Person for any Expenses which are a
result of the willful misconduct, bad faith or gross negligence of such
Indemnified Person.

      11. This Trust Agreement shall be governed by, and construed in accordance
with, the laws of the State of Delaware (without regard to conflict of laws
principles).



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      IN WITNESS WHEREOF, the parties hereto, intending to be legally bound,
have caused this Trust Agreement to be duly executed as of the date first
written above.


                                    UNION ELECTRIC COMPANY,
                                    as Depositor


                                    By:   /s/ JERRE E. BIRDSONG
                                          ------------------------------
                                          Name:  JERRE E. BIRDSONG
                                          Title: Vice President and Treasurer

                                    THE BANK OF NEW YORK (DELAWARE),
                                    as Delaware trustee


                                    By:   /s/ WILLIAM L. LEWIS
                                          ------------------------------
                                          Name:  WILLIAM L. LEWIS
                                          Title: Senior Vice President

                                    JERRE E. BIRDSONG,
                                    as Administrator

                                    /s/ JERRE E. BIRDSONG
                                    -------------------------------





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