RhoGAP_ARHGAP21: RhoGAP (GTPase-activator protein [GAP] for Rho-like small GTPases) domain of ArhGAP21-like proteins. ArhGAP21 is a multi-domain protein, containing RhoGAP, PH and PDZ domains, and is believed to play a role in the organization of the cell-cell junction complex. It has been shown to function as a GAP of Cdc42 and RhoA, and to interact with alpha-catenin and Arf6. 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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