The RAC GTPase Cycle
RAC, a member of the family of RHO-like GTPases, cycles between a GDP- and a GTP-bound state. When GTP-bound, it interacts with various effector molecules that elicit downstream responses including notably actin cytoskeletal reorganisation. Multiple mechanisms control RAC activity including control of nucleotide binding and hydrolysis by GEFs (Guanine Nucleotide Exchange Factors) and GTPase Activating Proteins (GAPs) respectively, regulation of subcellular localisation, modulation of RAC protein levels, and post-translational modification including isoprenylation and as we and others have demonstrated ubiquitylation and SUMOylation (Castillo-Lluva et al. Oncogene 2013; Castillo-Lluva et al. Nat Cell Biol. 2010).