RAC3 is a member of the Rac subfamily of the Rho small G proteins. This protein is a small (~21 kDa) monomeric GTP-binding protein, and is an important component of intracellular signalling pathway, including the control of cell growth, cytoskeletal reorganization, and the activation of protein kinases. Recombinant human RAC3 protein was expressed in E.coli and purified by using conventional chromatography techniques.