RAS p21 protein activator (GTPase activating protein) family pleckstrin homology (PH) domain
RASAL1, GAP1(m), GAP1(IP4BP), and CAPRI are all members of the GAP1 family of GTPase-activating proteins. They contain N-terminal SH2-SH3-SH2 domains, followed by two C2 domains, a PH domain, a RasGAP domain, and a BTK domain. With the notable exception of GAP1(m), they all possess an arginine finger-dependent GAP activity on the Ras-related protein Rap1. They act as a suppressor of RAS enhancing the weak intrinsic GTPase activity of RAS proteins resulting in the inactive GDP-bound form of RAS, allowing control of cellular proliferation and differentiation. PH domains share little sequence conservation, but all have a common fold, which is electrostatically polarized. 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.",