Bacterial flagellin-specific chaperone FliS interacts with anti-sigma factor FlgM

J Bacteriol. 2014 Mar;196(6):1215-21. doi: 10.1128/JB.01278-13. Epub 2014 Jan 10.


Flagella are extracellular organelles that propel bacteria. Each flagellum consists of a basal body, a hook, and a filament. The major protein of the filament is flagellin. Induction of flagellin gene expression coincides with secretion of FlgM. The role of FlgM is to inhibit FliA (σ(28)), a flagellum-specific RNA polymerase responsible for flagellin transcription. To prevent premature polymerization of newly synthesized flagellin molecules, FliS, the flagellin-specific chaperone, binds flagellin and facilitates its export. In this study, the interaction between FlgM and FliS from Salmonella enterica serovar Typhimurium was characterized using gel shift, intrinsic tryptophan fluorescence, circular dichroism, limited proteolysis, and cross-linking. We have demonstrated that (i) FliS and FlgM interact specifically, forming a 1:1 complex, (ii) the FliS binding site on FlgM is proximal to or even overlaps the binding site for FliA, and (iii) FliA competes with FliS for FlgM binding.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / metabolism*
  • Circular Dichroism
  • Cross-Linking Reagents / metabolism
  • Electrophoretic Mobility Shift Assay
  • Fluorometry
  • Protein Binding
  • Protein Interaction Mapping*
  • Proteolysis
  • Salmonella typhimurium / metabolism*
  • Sigma Factor / metabolism


  • Bacterial Proteins
  • Cross-Linking Reagents
  • FliA protein, Bacteria
  • Sigma Factor
  • FlgM protein, Bacteria
  • FliS protein, Bacteria