Probing the receptor recognition site of the FimH adhesin by fimbriae-displayed FimH-FocH hybrids.

Thomas Borch Knudsen, Per Klemm

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Type 1 fimbriae are surface organelles of Escherichia coli which mediate D-mannose-sensitive binding to different host surfaces.This binding is conferred by the minor fimbrial component FimH. The binding domain of the FimH adhesin has been studied byconstructing hybrids of FimH and a homologous protein, FocH, originating from F1C fimbriae. F1C fimbriae do not bind toD-mannosides or confer agglutination of any known types of erythrocytes or yeast. It was previously shown that the FocHprotein can be readily substituted by the FimH adhesin, resulting in hybrid fimbriae with the same binding characteristics as type1 fimbriae. The receptor binding of fimbriae-presented chimeric FimH-FocH hybrids was studied. FimH-FocH fusionsencompassing 72% of the N-terminus of FimH fused to the complementary sector of FocH conferred agglutination oferythrocytes and yeast cells at a comparable level to FimH. Surprisingly, it was also found that similar fusions containingbetween 56 and 66% FimH still conferred binding to yeast cells, D-mannose-BSA and D-mannose-beads but did not give riseto agglutination. The receptor binding capacity of fusions containing 50% or less of the FimH N-terminal region was virtuallyabolished. The results point to the presence of a D-mannose-receptor-binding core domain in FimH, the affinity of which ismodulated by other sectors of the protein to enable binding to extended mannose-containing targets.
Original languageEnglish
JournalMicrobiology 1998 Jul;144 ( Pt 7):1919-29
Issue number7
Pages (from-to)1919-29
Publication statusPublished - 1998

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