Ral GEF with PH domain and SH3 binding motif 1 and 2 Pleckstrin homology (PH) domain
RalGPS1 (also called Ral GEF with PH domain and SH3 binding motif 1;RALGEF2/ Ral guanine nucleotide exchange factor 2; RalA exchange factor RalGPS1; Ral guanine nucleotide exchange factor RalGPS1A2; ras-specific guanine nucleotide-releasing factor RalGPS1) and RalGPS2 (also called Ral GEF with PH domain and SH3 binding motif 2; Ral-A exchange factor RalGPS2; ras-specific guanine nucleotide-releasing factor RalGPS22). They activate small GTPase Ral proteins such as RalA and RalB by stimulating the exchange of Ral bound GDP to GTP, thereby regulating various downstream cellular processes. Structurally they contain an N-terminal Cdc25-like catalytic domain, followed by a PXXP motif and a C-terminal PH domain. The Cdc25-like catalytic domain interacts with Ral and its PH domain ensures the correct membrane localization. Its PXXP motif is thought to interact with the SH3 domain of Grb2. 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.",