title: Clustering of Escherichia coli type-1 fimbrial adhesins by using multimeric heptyl α-D-mannoside probes with a carbohydrate core.
abstract: Heptyl α-D-mannoside (HM) is a strong inhibitor of the FimH lectin that mediates the initial adhesion of the uropathogenic Escherichia coli (E. coli) to the bladder cells. We designed a set of multivalent HM ligands based on carbohydrate cores with structural valencies that range from 1 to 7. The chemical strategy used to construct the regular hydrophilic structures consisted of the repetition of a critical glucoside fragment. A primary amino group was grafted at the sugar reducing end to couple the multimers to a fluorescent label. A one-pot synthetic approach was developed to tether the ligands and the fluorescein isothiocyanate (FITC) probe to the scaffold simultaneously. Isothermal calorimetry with the monomeric FimH lectin revealed nanomolar affinities and saturation of all structurally available binding sites on the multivalent HM ligands. Direct titrations domain showed almost strict correlation of enthalpy-entropy compensation with increasing valency of the ligand, whereas reverse titration calorimetry demonstrated negative cooperativity between the first and the second binding site of the divalent heptyl mannoside. A multivalency effect was nevertheless observed by inhibiting the haemagglutination of type-1 piliated UTI89 E. coli, with a titer as low as 60 nM for the heptavalent HM ligand. An FITC-labeled HM trimer showed capture and cross-linking of living bacteria in solution, a phenomenon not previously described with low-valency ligands.
authors.affiliation: Laboratoire des Glucides UMR CNRS 6219, Institut de Chimie de Picardie, UFR des Sciences, Université de Picardie Jules Verne, 33 rue Saint-Leu, 80039 Amiens Cedex 1, France.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Almant
authors.forename: Vincent
authors.initials: V
authors.lastname: Moreau
authors.forename: José
authors.initials: J
authors.lastname: Kovensky
authors.forename: Julie
authors.initials: J
authors.lastname: Bouckaert
authors.forename: Sébastien G
authors.initials: SG
authors.lastname: Gouin
mesh_terms: D018830:Adhesins, Escherichia coli / Q000737:chemistry*; D002151:Calorimetry / Q000379:methods; D019277:Entropy; D004926:Escherichia coli / Q000737:chemistry*; D036781:Fimbriae Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry*; D016650:Fluorescein-5-isothiocyanate / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D006384:Hemagglutination; D008024:Ligands; D008362:Mannosides / Q000737:chemistry*; D017434:Protein Structure, Tertiary
chemical_list: D018830:Adhesins, Escherichia coli; D005456:Fluorescent Dyes; D008024:Ligands; D008362:Mannosides; C058769:fimH protein, E coli; D036781:Fimbriae Proteins; D016650:Fluorescein-5-isothiocyanate