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Exchange Factor for ARF6 Pleckstrin homology (PH) domain EFA6 (also called PSD/pleckstrin and Sec7 domain containing) is an guanine nucleotide exchange factor for ADP ribosylation factor 6 (ARF6), which is involved in membrane recycling. EFA6 has four structurally related polypeptides: EFA6A, EFA6B, EFA6C and EFA6D. It consists of a N-terminal proline rich region (PR), a SEC7 domain, a PH domain, a PR, a coiled-coil region, and a C-terminal PR. The EFA6 PH domain regulates its association with the plasma membrane. EFA6 activates Arf6 through its Sec7 catalytic domain and modulates this activity through its C-terminal domain, which rearranges the actin cytoskeleton in fibroblastic cell lines. 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.",