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Bud emergence protein 3 (Bem3) Pleckstrin homology (PH) domain Bud emergence in Saccharomyces cerevisiae involves cell cycle-regulated reorganizations of cortical cytoskeletal elements and requires the action of the Rho-type GTPase Cdc42. Bem3 contains a RhoGAP domain and a PH domain. Though Bem3 and Bem2 both contain a RhoGAP, but only Bem3 is able to stimulate the hydrolysis of GTP on Cdc42. Bem3 is thought to be the GAP for Cdc42. 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.",