Tohru Kozasa

TL;DR: 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).

TL;DR: The GTPase activities of two G protein alpha subunits, Galpha12 and Galpha13, are stimulated by the Rho guanine nucleotide exchange factor p115 RhoGEF, which can directly link heterotrimeric G proteinalpha subunits to regulation of Rho.

TL;DR: It is demonstrated here that two RGS proteins, RGS4 and GAIP, also act as GAPs for Gq alpha, the G alpha protein responsible for activation of phospholipase C beta, and block activation by guanosine 5'-(3-O-thio) triphosphate-Gq alpha.

TL;DR: RGS4 stabilizes the transition state for GTP hydrolysis, as evidenced by its high affinity for the GDP-AlF4−-bound forms of Goα and Giα and its relatively low affinity forThe GTPγS- and GDP- bound forms of these proteins.

TL;DR: In vitro analysis revealed that GRK2 possesses weak GAP activity toward Gαq that is dependent on the presence of a G protein-coupled receptor, and data suggest that a subfamily of the GRKs may be bifunctional regulators of G Protein-Coupled receptors signaling operating directly on both receptors and G proteins.