Members of the Rho （or ARH） protein family and other Ras-related small GTP-binding proteins are involved in various cellular procedures， such as cell cytoskeletal organization， secretion， proliferation， and signaling. The GTPBPs are active only in the GTP-bound state. At least 3 types of proteins firmly regulate cycling between the GTP-bound and GDP-bound states: GDP-dissociation inhibitors （GDIs）， GTPase-activating proteins （GAPs） and guanine nucleotide-releasing factors （GRFs）. ARHGDIB and the other GDIs lower the level of GDP dissociation from Ras-like GTPases.
