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Stomatal Closure Related Actin-Binding Protein 1 Pleckstrin homology-like domain SCAB1 is an actin-binding protein that interacts with actin filaments and regulates stomatal movement. SCAB1 is composed of an actin-binding domain, two coiled-coil (CC) domains, and a fused immunoglobulin (Ig) and PH (Ig-PH) domain. SCAB1 homologs are widely present, often in multiple copies (three in Arabidopsis), in plants including eudicots, monocots, ferns and mosses, but are not found in algae and non-plant species. The C-terminal PH domain binds weakly with inositol phosphates via an atypical basic surface patch. SCAB1 forms a dimeric structure via its coiled-coil domains. 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.",