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                                                                    EXHIBIT 4.12

                        UNION ELECTRIC CAPITAL TRUST ___
                                 TRUST AGREEMENT

     THIS TRUST AGREEMENT, dated as of ______________, 200_, is by and between
(i) Union Electric Company, a Missouri corporation (the "Depositor"), (ii) [name
of Delaware trustee], a Delaware banking corporation, as Delaware trustee (the
"Delaware Trustee"), and (iii) [name of administrative trustee], as
administrative trustee (the "Administrative Trustee," and together with the
Delaware Trustee, the "Trustees"). The Depositor and the Trustees hereby agree
as follows:

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

     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
Trustees hereby declare that they 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. ss. 3801 ET SEQ. (the "Business Trust Act"), and that this document
constitutes the governing instrument of the Trust.

     4.  The Trustees are 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 Trustees 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 Trustees and the Depositor 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
Trustees 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 Trustees may take all actions deemed proper as are necessary
to effect the transactions contemplated herein.

     6.  The Depositor and the Trustees 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,

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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 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; and (iv) 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 Trustees, the Trustees, in their capacity as trustees 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 [name
of Delaware 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, each of the Trustees, solely in its capacity as
trustee of the Trust, and the Depositor hereby constitutes and appoints [     ],
and each of them severally, 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 two (2) 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

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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.

     9.  [Name of Delaware trustee], in its capacity as trustee of the Trust,
shall not have any of the powers or duties of the Trustees as set forth herein
and 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. 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:
                                               ---------------------------

                                            [NAME OF DELAWARE TRUSTEE],
                                            as Delaware trustee, and not in its
                                            individual capacity

                                         By:

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

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

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