p115 RhoGEF, a GTPase Activating Protein for Gα 12 and Gα 13

Members of the regulators of G protein signaling (RGS) family stimulate the intrinsic guanosine triphosphatase (GTPase) activity of the α subunits of certain heterotrimeric guanine nucleotide–binding proteins (G proteins). The guanine nucleotide exchange factor (GEF) for Rho, p115 RhoGEF, has an amino-terminal region with similarity to RGS proteins. Recombinant p115 RhoGEF and a fusion protein containing the amino terminus of p115 had specific activity as GTPase activating proteins toward the α subunits of the G proteins G 12 and G 13 , but not toward members of the G s , G i , or G q subfamilies of Gα proteins. This GEF may act as an intermediary in the regulation of Rho proteins by G 13 and G 12 .