Exhibit 4.3 TWENTY-FIRST SUPPLEMENTAL INDENTURE This instrument was drafted by and should be returned to: Leslie P. Recht COUNTERPART NO. ___________ Defrees & Fiske 200 S. Michigan Avenue Suite 1100 Chicago, Illinois 60604-2480 (312) 372-4000...Supplemental Indenture • January 10th, 2002 • Alliant Energy Corp • Electric & other services combined
