RhoGAP_GMIP_PARG1: RhoGAP (GTPase-activator protein [GAP] for Rho-like small GTPases) domain of GMIP (Gem interacting protein) and PARG1 (PTPL1-associated RhoGAP1). GMIP plays important roles in neurite growth and axonal guidance, and interacts with Gem, a member of the RGK subfamily of the Ras small GTPase superfamily, through the N-terminal half of the protein. GMIP contains a C-terminal RhoGAP domain. GMIP inhibits RhoA function, but is inactive towards Rac1 and Cdc41. PARG1 interacts with Rap2, also a member of the Ras small GTPase superfamily whose exact function is unknown, and shows strong preference for Rho. Small GTPases cluster into distinct families, and all act as molecular switches, active in their GTP-bound form but inactive when GDP-bound. The Rho family of GTPases activates effectors involved in a wide variety of developmental processes, including regulation of cytoskeleton formation, cell proliferation and the JNK signaling pathway. GTPases generally have a low intrinsic GTPase hydrolytic activity but there are family-specific groups of GAPs that enhance the rate of GTP hydrolysis by several orders of magnitude.
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