RhoGAP_chimaerin: RhoGAP (GTPase-activator protein [GAP] for Rho-like small GTPases) domain of chimaerins. Chimaerins are a family of phorbolester- and diacylglycerol-responsive GAPs specific for the Rho-like GTPase Rac. Chimaerins exist in two alternative splice forms that each contain a C-terminal GAP domain, and a central C1 domain which binds phorbol esters, inducing a conformational change that activates the protein; one splice form is lacking the N-terminal Src homology-2 (SH2) domain. 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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