Background: Escherichia coli strains adhere to the normally sterile human uroepithelium using type 1 pili, that are long, hairy surface organelles exposing a mannose-binding FimH adhesin at the tip. A small percentage of adhered bacteria can successfully invade bladder cells, presumably via pathways mediated by the high-mannosylated uroplakin-Ia and a3b1 integrins found throughout the uroepithelium. Invaded bacteria replicate and mature into dense, biofilm-like inclusions in preparation of fluxing and of infection of neighbouring cells, being the major cause of the troublesome recurrent urinary tract infections. Methodology/Principal Findings:We demonstrate that a-D-mannose based inhibitors of FimH not only block bacterial adhesion on uroepithelial cells but also antagonize invasion and biofilm formation. Heptyl a-D-mannose prevents binding of type 1-piliated E. coli to the human bladder cell line 5637 and reduces both adhesion and invasion of the UTI89 cystitis isolate instilled in mouse bladder via catheterization. Heptyl a-D-mannose also specifically inhibited biofilm formation at micromolar concentrations. The structural basis of the great inhibitory potential of alkyl and aryl a-D-mannosides was elucidated in the crystal structure of the FimH receptor-binding domain in complex with oligomannose-3. FimH interacts with Mana1,3Manb1,4GlcNAcb1,4GlcNAc in an extended binding site. The interactions along the a1,3 glycosidic bond and the first b1,4 linkage to the chitobiose unit are conserved with those of FimH with butyl a-D-mannose. The strong stacking of the central mannose with the aromatic ring of Tyr48 is congruent with the high affinity found for synthetic inhibitors in which this mannose is substituted for by an aromatic group.Conclusions/Significance: The potential of ligand-based design of antagonists of urinary tract infections is ruled by the structural mimicry of natural epitopes and extends into blocking of bacterial invasion, intracellular growth and capacity to fluxing and of recurrence of the infection.

The crystal structures of cadmium/cadmium and zinc/calcium concanavalin A (con A) at pH 5.0 and pH 6.15, respectively, were determined. The structure of cadmium/cadmium con A con®rms that the secondary Cd 2+ -binding site S3 is empty at pH 5. The metal-binding sites S1 and S2 are only very slightly affected by the substitution with cadmium. On the other hand, S1 and S2 and most of the protein surface of zinc/calcium con A at pH 6.15 differ from other fully metal-bound and carbohydrate-free structures. Most of these structural differences at the protein surface are a result of the interplay between metal binding, protonation and crystal packing. This interplay is expressed by relative rotations and translations of the con A units in alternative crystal packings and participation in space-group conversions inside crystals in situ. The particular crystal packing of zinc/calcium con A creates a novel zinc-binding site S4. The Zn 2+ ion in S4 ligates two aspartates from one tetramer and a histidine from a symmetryrelated tetramer.

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