UNION ELECTRIC CO

Ameren, formed in 1997 and headquartered in St. Louis, Missouri, is a public utility holding company that primarily holds equity interests in its subsidiaries. Ameren's operations depend on distributions from its subsidiaries, which are separate legal entities. Its principal subsidiaries are Ameren Missouri, Ameren Illinois, and ATXI. Ameren Missouri operates a rate-regulated electric generation, transmission, and distribution business, as well as a rate-regulated natural gas distribution business, both within Missouri. Ameren Illinois operates rate-regulated electric transmission, electric distribution, and natural gas distribution businesses in Illinois. ATXI operates a FERC rate-regulated electric transmission business in the MISO region. Ameren has four business segments: Ameren Missouri, Ameren Illinois Electric Distribution, Ameren Illinois Natural Gas, and Ameren Transmission. The Ameren Missouri segment encompasses all operations of Ameren Missouri. The Ameren Illinois Electric Distribution segment covers the electric distribution business of Ameren Illinois. The Ameren Illinois Natural Gas segment includes the natural gas business of Ameren Illinois. The Ameren Transmission segment primarily combines the electric transmission businesses of Ameren Illinois and ATXI.