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The fimbrial adhesin F17‐G of enterotoxigenic Escherichia coli has an immunoglobulin‐like lectin domain that binds N ‐acetylglucosamine
Author(s) -
Buts Lieven,
Bouckaert Julie,
De Genst Erwin,
Loris Remy,
Oscarson Stefan,
Lahmann Martina,
Messens Joris,
Brosens Elke,
Wyns Lode,
De Greve Henri
Publication year - 2003
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2003.03600.x
Subject(s) - fimbria , bacterial adhesin , biology , immunoglobulin domain , pilus , lectin , enterotoxigenic escherichia coli , microbiology and biotechnology , escherichia coli , pilin , biochemistry , receptor , gene , enterotoxin
Summary The F17‐G adhesin at the tip of flexible F17 fimbriae of enterotoxigenic Escherichia coli mediates binding to N ‐acetyl‐β‐ d ‐glucosamine‐presenting receptors on the microvilli of the intestinal epithelium of ruminants. We report the 1.7 Å 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 β‐strand G of the immunoglobulin‐like fold and provides new insights into pilus assembly, function and adhesion.