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ArfGAP with SH3 domain, ankyrin repeat and PH domain Pleckstrin homology (PH) domain ASAPs (ASAP1, ASAP2, and ASAP3) function as an Arf-specific GAPs, participates in rhodopsin trafficking, is associated with tumor cell metastasis, modulates phagocytosis, promotes cell proliferation, facilitates vesicle budding, Golgi exocytosis, and regulates vesicle coat assembly via a Bin/Amphiphysin/Rvs domain. ASAPs contain an NH2-terminal BAR domain, a tandem PH domain/GAP domain, three ankyrin repeats, two proline-rich regions, and a COOH-terminal Src homology 3 (SH3) 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.",