Flagellin polymerisation control by a cytosolic export chaperone

J Mol Biol. 2001 Apr 27;308(2):221-9. doi: 10.1006/jmbi.2001.4597.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Biopolymers / chemistry
  • Biopolymers / metabolism
  • Chromatography, Gel
  • Cytosol / chemistry*
  • Dimerization
  • Flagella / chemistry
  • Flagella / metabolism
  • Flagellin / chemistry*
  • Flagellin / genetics
  • Flagellin / metabolism*
  • Flagellin / ultrastructure
  • Microscopy, Electron
  • Molecular Chaperones / genetics
  • Molecular Chaperones / metabolism*
  • Protein Binding
  • Protein Subunits
  • Protein Transport
  • Salmonella typhimurium / cytology
  • Salmonella typhimurium / genetics
  • Salmonella typhimurium / metabolism*
  • Sequence Deletion
  • Solubility
  • Substrate Specificity


  • Bacterial Proteins
  • Biopolymers
  • Molecular Chaperones
  • Protein Subunits
  • Flagellin
  • FliS protein, Bacteria