Ameren is a public utility holding company. Through its subsidiary, Union Electric Company, Co. operates a rate-regulated electric generation, transmission, and distribution business and a rate-regulated natural gas distribution business in Missouri. Through its subsidiary, Ameren Illinois Company, Co. operates rate-regulated electric transmission, electric distribution, and natural gas distribution businesses in Illinois. Through its Ameren Transmission Company of Illinois subsidiary, Co. operates a Federal Energy Regulatory Commission rate-regulated electric transmission business. Co. also has other subsidiaries that conduct other activities, such as providing shared services.