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Evectin Pleckstrin homology (PH) domain There are 2 members of the evectin family (also called pleckstrin homology domain containing, family B): evt-1 (also called PLEKHB1) and evt-2 (also called PLEKHB2). evt-1 is specific to the nervous system, where it is expressed in photoreceptors and myelinating glia. evt-2 is widely expressed in both neural and nonneural tissues. Evectins possess a single N-terminal PH domain and a C-terminal hydrophobic region. evt-1 is thought to function as a mediator of post-Golgi trafficking in cells that produce large membrane-rich organelles. It is a candidate gene for the inherited human retinopathy autosomal dominant familial exudative vitreoretinopathy and a susceptibility gene for multiple sclerosis. evt-2 is essential for retrograde endosomal membrane transport from the plasma membrane (PM) to the Golgi. Two membrane trafficking pathways pass through recycling endosomes: a recycling pathway and a retrograde pathway that links the PM to the Golgi/ER. Its PH domain that is unique in that it specifically recognizes phosphatidylserine (PS), but not polyphosphoinositides. PS is an anionic phospholipid class in eukaryotic biomembranes, is highly enriched in the PM, and plays key roles in various physiological processes such as the coagulation cascade, recruitment and activation of signaling molecules, and clearance of apoptotic cells. PH domains are only found in eukaryotes. They 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.",