Electric and gas services supplier, Ameren Corporation, has appointed Gregory Nelson as senior vice president and general counsel, effective March 2. He assumes the role from Steven Sullivan, who will become chairman, president and CEO of Ameren Energy Resources Company, Ameren's holding company for merchant generation and its energy marketing services.

Nelson, who has been with Ameren the last 15 years, most recently served as vice president and tax counsel, responsible for the federal, state and local tax compliance and planning functions for the Ameren group of corporations. He joined Ameren (then called Union Electric Company) in 1995 as manager of the tax department.

From 1988 through 1995, Nelson was associated with the Washington, D.C. office of the law firm Reid & Priest, where he represented investor-owned electric utilities and the Edison Electric Institute in taxation matters. Earlier in this career, he served as a trial attorney with the Tax Division of the Department of Justice, where he specialized in civil tax litigation.