4djg
From Proteopedia
Crystal structure of the coiled-coil 1 domain of actin-binding protein SCAB1
Structural highlights
Function[SCAB1_ARATH] Plant-specific actin binding protein that bundles and stabilizes microfilaments (MFs). Has no nucleation or capping activity. Regulates MF reorganization during stomatal closure. The binding to F-actin is insensitive to Ca(2+) and pH. Binds weakly to inositol phosphates (PubMed:22356912).[1] [2] Publication Abstract from PubMedSCAB1 is a novel plant-specific actin-binding protein that binds, bundles, and stabilizes actin filaments and regulates stomatal movement. Here, we dissected the structure and function of SCAB1 by structural and biochemical approaches. We show that SCAB1 is composed of an actin-binding domain, two coiled-coil (CC) domains, and a fused immunoglobulin and pleckstrin homology (Ig-PH) domain. We determined crystal structures for the CC1 and Ig-PH domains at 1.9 and 1.7 A resolution, respectively. The CC1 domain adopts an antiparallel helical hairpin that further dimerizes into a four-helix bundle. The CC2 domain also mediates dimerization. At least one of the coiled coils is required for actin binding, indicating that SCAB1 is a bivalent actin cross-linker. The key residues required for actin binding were identified. The PH domain lacks a canonical basic phosphoinositide-binding pocket but can bind weakly to inositol phosphates via a basic surface patch, implying the involvement of inositol signaling in SCAB1 regulation. Our results provide novel insights into the functional organization of SCAB1. Plant actin-binding protein SCAB1 is dimeric actin cross-linker with atypical pleckstrin homology domain.,Zhang W, Zhao Y, Guo Y, Ye K J Biol Chem. 2012 Apr 6;287(15):11981-90. Epub 2012 Feb 22. PMID:22356912[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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