The fimbrial adhesin F17-G of enterotoxigenic Escherichia coli has an immunoglobulin-like lectin domain that binds N-acetylglucosamine

Mol Microbiol. 2003 Aug;49(3):705-15. doi: 10.1046/j.1365-2958.2003.03600.x.


The F17-G adhesin at the tip of flexible F17 fimbriae of enterotoxigenic Escherichia coli mediates binding to N-acetyl-beta-D-glucosamine-presenting receptors on the microvilli of the intestinal epithelium of ruminants. We report the 1.7 A resolution crystal structure of the lectin domain of F17-G, both free and in complex with N-acetylglucosamine. The monosaccharide is bound on the side of the ellipsoid-shaped protein in a conserved site around which all natural variations of F17-G are clustered. A model is proposed for the interaction between F17-fimbriated E. coli and microvilli with enhanced affinity compared with the binding constant we determined for F17-G binding to N-acetylglucosamine (0.85 mM-1). Unexpectedly, the F17-G structure reveals that the lectin domains of the F17-G, PapGII and FimH fimbrial adhesins all share the immunoglobulin-like fold of the structural components (pilins) of their fimbriae, despite lack of any sequence identity. Fold comparisons with pilin and chaperone structures of the chaperone/usher pathway highlight the central role of the C-terminal beta-strand G of the immunoglobulin-like fold and provides new insights into pilus assembly, function and adhesion.

Publication types

  • Comparative Study

MeSH terms

  • Acetylglucosamine / metabolism*
  • Adhesins, Bacterial / chemistry*
  • Adhesins, Bacterial / metabolism
  • Adhesins, Escherichia coli / chemistry*
  • Adhesins, Escherichia coli / metabolism
  • Amino Acid Sequence
  • Animals
  • Bacterial Adhesion / physiology*
  • Binding Sites
  • Carbohydrate Metabolism
  • Crystallography, X-Ray
  • Escherichia coli / metabolism*
  • Escherichia coli / physiology
  • Escherichia coli Proteins / chemistry*
  • Escherichia coli Proteins / metabolism
  • Fimbriae Proteins / chemistry
  • Fimbriae Proteins / metabolism
  • Fimbriae, Bacterial / metabolism*
  • Kinetics
  • Lectins / chemistry*
  • Lectins / metabolism
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Binding
  • Protein Conformation
  • Protein Folding
  • Protein Structure, Tertiary
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Structure-Activity Relationship
  • Substrate Specificity


  • Adhesins, Bacterial
  • Adhesins, Escherichia coli
  • Escherichia coli Proteins
  • F17-G protein, E coli
  • Lectins
  • PapG protein, E coli
  • fimH protein, E coli
  • Fimbriae Proteins
  • Acetylglucosamine