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Structural basis of tropism of Escherichia coli to the bladder during urinary tract infection.

Molecular microbiology (2002-05-16)
Chia-Suei Hung, Julie Bouckaert, Danielle Hung, Jerome Pinkner, Charlotte Widberg, Anthony DeFusco, C Gale Auguste, Robert Strouse, Solomon Langermann, Gabriel Waksman, Scott J Hultgren
ABSTRACT

The first step in the colonization of the human urinary tract by pathogenic Escherichia coli is the mannose-sensitive binding of FimH, the adhesin present at the tip of type 1 pili, to the bladder epithelium. We elucidated crystallographically the interactions of FimH with D-mannose. The unique site binding pocket occupied by D-mannose was probed using site-directed mutagenesis. All but one of the mutants examined had greatly diminished mannose-binding activity and had also lost the ability to bind human bladder cells. The binding activity of the mono-saccharide D-mannose was delineated from this of mannotriose (Man(alpha 1-3)[Man(alpha 1-6)]Man) by generating mutants that abolished D-mannose binding but retained mannotriose binding activity. Our structure/function analysis demonstrated that the binding of the monosaccharide alpha-D-mannose is the primary bladder cell receptor for uropathogenic E. coli and that this event requires a highly conserved FimH binding pocket. The residues in the FimH mannose-binding pocket were sequenced and found to be invariant in over 200 uropathogenic strains of E. coli. Only enterohaemorrhagic E. coli (EHEC) possess a sequence variation within the mannose-binding pocket of FimH, suggesting a naturally occurring mechanism of attenuation in EHEC bacteria that would prevent them from being targeted to the urinary tract.

MATERIALS
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Brand
Product Description

Sigma-Aldrich
D-(+)-Mannose, powder, BioReagent, suitable for cell culture
Millipore
D-(+)-Mannose, ≥99.0% (sum of enantiomers, HPLC), suitable for microbiology
Sigma-Aldrich
D-(+)-Mannose, BioUltra, ≥99.5% (sum of enantiomers, HPLC)
Millipore
D-(+)-Mannose, suitable for microbiology, ≥99%
Sigma-Aldrich
D-(+)-Mannose, wood, ≥99%