?
Sesquipedalian family Pleckstrin homology (PH) domain The sesquipedalian family has 2 mammalian members: Ses1 and Ses2, which are also callled 7 kDa inositol polyphosphate phosphatase-interacting protein 1 and 2. They play a role in endocytic trafficking and are required for receptor recycling from endosomes, both to the trans-Golgi network and the plasma membrane. Members of this family form homodimers and heterodimers. Sesquipedalian interacts with inositol polyphosphate 5-phosphatase OCRL-1 (INPP5F) also known as Lowe oculocerebrorenal syndrome protein, a phosphatase enzyme that is involved in actin polymerization and is found in the trans-Golgi network and INPP5B. Sesquipedalian contains a single PH 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.",