In mammals, Rac exists as three isoforms, Rac1, Rac2 and Rac3, which are highly similar in sequence. Rac and Cdc42 play key signaling roles in cytoskeletal reorganization, membrane trafficking, transcriptional regulation, cell growth and development. GTP binding stimulates the activity of Rac/Cdc42, and the hydrolysis of GTP to GDP through the proteins intrinsic GTPase activity, rendering it inactive.
