Toll-like receptor 5 recognizes a conserved site on flagellin required for protofilament formation and bacterial motility

Nat Immunol. 2003 Dec;4(12):1247-53. doi: 10.1038/ni1011. Epub 2003 Nov 16.


Toll-like receptor 5 (TLR5) recognizes bacterial flagellin and activates host inflammatory responses. In this study, we examine the nature of the TLR5-flagellin interaction. With deletional, insertional and alanine-scanning mutagenesis, we precisely mapped the TLR5 recognition site on flagellin to a cluster of 13 amino acid residues that participate in intermolecular interactions within flagellar protofilaments and that are required for bacterial motility. The recognition site is buried in the flagellar filament, and monomeric flagellin, but not the filamentous molecule, stimulated TLR5. Finally, flagellin coprecipitated with TLR5, indicating close physical interaction between the molecules. These studies demonstrate the exquisite ability of the innate immune system to precisely target a conserved site on flagellin that is essential for bacterial motility.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alanine
  • Amino Acid Sequence
  • Animals
  • Binding Sites
  • CHO Cells
  • Cricetinae
  • Cricetulus
  • Flagella / chemistry
  • Flagella / physiology
  • Flagella / ultrastructure
  • Flagellin / chemistry
  • Flagellin / genetics
  • Flagellin / metabolism*
  • Flagellin / ultrastructure
  • Humans
  • Membrane Glycoproteins / chemistry
  • Membrane Glycoproteins / physiology*
  • Mice
  • Microscopy, Electron
  • Molecular Sequence Data
  • Point Mutation
  • Polymerase Chain Reaction
  • Protein Structure, Quaternary
  • Receptors, Cell Surface / chemistry
  • Receptors, Cell Surface / physiology*
  • Toll-Like Receptor 5
  • Toll-Like Receptors


  • Membrane Glycoproteins
  • Receptors, Cell Surface
  • TLR5 protein, human
  • Toll-Like Receptor 5
  • Toll-Like Receptors
  • Flagellin
  • Alanine