St. Louis-based Ameren Corporation has announced plans to purchase the parent of Central Illinois Light Company for $541-Million from AES Corporation. Ameren, already the largest electric provider in Missouri through its AmerenUE subsidiary, will operate Central Illinois Light when the deal closes in about a year. Under terms of the deal, Ameren will also assume $859-Million in debt. The buyout still has to be approved by several regulatory agencies, including the Illinois Commerce Commission and the Federal Energy Regulatory Commission. Ameren currently provides service though its subsidiaries to about 1.8-Million customers in Missouri and Illinois.