2llf | pdb_00002llf
Sixth Gelsolin-like domain of villin in 5 mM CaCl2
Structural highlights
FunctionVILI_CHICK Epithelial cell-specific Ca(2+)-regulated actin-modifying protein that modulates the reorganization of microvillar actin filaments. Plays a role in the actin nucleation, actin filament bundle assembly, actin filament capping and severing. Binds phosphatidylinositol 4,5-bisphosphate (PIP2) and lysophosphatidic acid (LPA); binds LPA with higher affinity than PIP2. Binding to LPA increases its phosphorylation by SRC and inhibits all actin-modifying activities. Binding to PIP2 inhibits actin-capping and -severing activities but enhances actin-bundling activity. Regulates the intestinal epithelial cell morphology, cell invasion, cell migration and apoptosis. Protects against apoptosis induced by dextran sodium sulfate (DSS) in the gastrointestinal epithelium. Appears to regulate cell death by maintaining mitochondrial integrity. Enhances hepatocyte growth factor (HGF)-induced epithelial cell motility, chemotaxis and wound repair (By similarity). Its actin-bundling activity is inhibited by tropomyosin.[1] [2] Publication Abstract from PubMedVillin is a gelsolin-like cytoskeleton regulator localized in the brush border at the apical end of epithelial cells. Villin regulates microvilli by bundling F-actin at low calcium levels and severing it at high calcium levels. The villin polypeptide consists of six gelsolin-like repeats (V1-V6) and the unique, actin binding C-terminal headpiece domain (HP). Villin modular fragment V6-HP requires calcium to stay monomeric and bundle F-actin. Our data show that isolated V6 is monomeric and does not bind F-actin at any level of calcium. We propose that the 40-residue unfolded V6-to-HP linker can be a key regulatory element in villin's functions such as its interactions with F-actin. Here we report a calcium-bound solution nuclear magnetic resonance (NMR) structure of V6, which has a gelsolin-like fold with the long alpha-helix in the extended conformation. Intrinsic tryptophan fluorescence quenching reveals two-Kd calcium binding in V6 (Kd1 of 22 muM and Kd2 of 2.8 mM). According to our NMR data, the conformation of V6 responds the most to micromolar calcium. We show that the long alpha-helix and the adjacent residues form the calcium-sensitive elements in V6. These observations are consistent with the calcium activation of F-actin severing by villin analogous to the gelsolin helix-straightening mechanism. Gelsolin-like activation of villin: calcium sensitivity of the long helix in domain 6.,Fedechkin SO, Brockerman J, Pfaff DA, Burns L, Webb T, Nelson A, Zhang F, Sabantsev AV, Melnikov AS, McKnight CJ, Smirnov SL Biochemistry. 2013 Nov 12;52(45):7890-900. doi: 10.1021/bi400699s. Epub 2013 Oct , 29. PMID:24070253[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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