title: Flagellin polymerisation control by a cytosolic export chaperone.
abstract: Assembly of the long helical filament of the bacterial flagellum requires polymerisation of ca 20,000 flagellin (FliC) monomeric subunits into the growing structure extending from the cell surface. Here, we show that export of Salmonella flagellin is facilitated specifically by a cytosolic protein, FliS, and that FliS binds to the FliC C-terminal helical domain, which contributes to stabilisation of flagellin subunit interactions during polymerisation. Stable complexes of FliS with flagellin were assembled efficiently in vitro, apparently by FliS homodimers binding to FliC monomers. The data suggest that FliS acts as a substrate-specific chaperone, preventing premature interaction of newly synthesised flagellin subunits in the cytosol. Compatible with this view, FliS was able to prevent in vitro polymerisation of FliC into filaments.
authors.affiliation: Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.
authors.forename: F
authors.initials: F
authors.lastname: Auvray
authors.forename: J
authors.initials: J
authors.lastname: Thomas
authors.forename: G M
authors.initials: GM
authors.lastname: Fraser
authors.forename: C
authors.initials: C
authors.lastname: Hughes
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001704:Biopolymers / Q000737:chemistry / Q000378:metabolism; D002850:Chromatography, Gel; D003600:Cytosol / Q000737:chemistry*; D019281:Dimerization; D005407:Flagella / Q000737:chemistry / Q000378:metabolism; D005408:Flagellin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D008854:Microscopy, Electron; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D021122:Protein Subunits; D021381:Protein Transport; D012486:Salmonella typhimurium / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D012995:Solubility; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D001704:Biopolymers; D018832:Molecular Chaperones; D021122:Protein Subunits; D005408:Flagellin; C076734:FliS protein, Bacteria