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

TitleThe fimbrial adhesin F17-G of enterotoxigenic Escherichia coli has an immunoglobulin-like lectin domain that binds N-acetylglucosamine.
Publication TypeJournal Article
Year of Publication2003
AuthorsButs, L., J. Bouckaert, E. De Genst, R. Loris, S. Oscarson, M. Lahmann, J. Messens, E. Brosens, L. Wyns, and H. De Greve
JournalMol Microbiol
Volume49
Issue3
Pagination705-15
Date Published2003 Aug
ISSN0950-382X
KeywordsAcetylglucosamine, Adhesins, Bacterial, Adhesins, Escherichia coli, Amino Acid Sequence, Animals, Bacterial Adhesion, Binding Sites, Carbohydrate Metabolism, Crystallography, X-Ray, Escherichia coli, Escherichia coli Proteins, Fimbriae Proteins, Fimbriae, Bacterial, Kinetics, Lectins, 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
Abstract

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.

Alternate JournalMol. Microbiol.
PubMed ID12864853
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