Rho family members regulate the cytoskeleton, cell growth and transcription. There are two closely related isoforms of Rac (Rac1 and Rac2) which differ in primarily in their C-termini, where Rac1 contains polybasic amino acid residues while Rac2 is less basic. Rac has been implicated in regulation of the cytoskeleton, the mitogenic response, superoxide generation in both phagocytes and transformed cells, and in regulation of transcription. Its known direct targets include the NADPH oxidase and PAK (p21-Activated Kinase).