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Rho GTPase activating protein 2 Pleckstrin homology (PH) domain RhoGAP2 (also called RhoGap22 or ArhGap22) are involved in cell polarity, cell morphology and cytoskeletal organization. They activate a GTPase belonging to the RAS superfamily of small GTP-binding proteins. The encoded protein is insulin-responsive, is dependent on the kinase Akt, and requires the Akt-dependent 14-3-3 binding protein which binds sequentially to two serine residues resulting in regulation of cell motility. Members here contain an N-terminal PH domain followed by a RhoGAP domain and either a BAR or TATA Binding Protein (TBP) Associated Factor 4 (TAF4) domain. PH domains have diverse functions, but in general are involved in targeting proteins to the appropriate cellular location or in the interaction with a binding partner. They share little sequence conservation, but all have a common fold, which is electrostatically polarized. Less than 10% of PH domains bind phosphoinositide phosphates (PIPs) with high affinity and specificity. PH domains are distinguished from other PIP-binding domains by their specific high-affinity binding to PIPs with two vicinal phosphate groups: PtdIns(3,4)P2, PtdIns(4,5)P2 or PtdIns(3,4,5)P3 which results in targeting some PH domain proteins to the plasma membrane. A few display strong specificity in lipid binding. Any specificity is usually determined by loop regions or insertions in the N-terminus of the domain, which are not conserved across all PH domains. PH domains are found in cellular signaling proteins such as serine/threonine kinase, tyrosine kinases, regulators of G-proteins, endocytotic GTPases, adaptors, as well as cytoskeletal associated molecules and in lipid associated enzymes. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",