title: Mutation of Tyr137 of the universalEscherichia colifimbrial adhesin FimH relaxes the tyrosine gate prior to mannose binding.
abstract: The most prevalent diseases manifested byEscherichia coliare acute and recurrent bladder infections and chronic inflammatory bowel diseases such as Crohn's disease.E. coliclinical isolates express the FimH adhesin, which consists of a mannose-specific lectin domain connectedviaa pilin domain to the tip of type 1 pili. Although the isolated FimH lectin domain has affinities in the nanomolar range for all high-mannosidic glycans, differentiation between these glycans is based on their capacity to form predominantly hydrophobic interactions within the tyrosine gate at the entrance to the binding pocket. In this study, novel crystal structures of tyrosine-gate mutants of FimH, ligand-free or in complex with heptyl α-d-O-mannopyranoside or 4-biphenyl α-d-O-mannopyranoside, are combined with quantum-mechanical calculations and molecular-dynamics simulations. In the Y48A FimH crystal structure, a large increase in the dynamics of the alkyl chain of heptyl α-d-O-mannopyranoside attempts to compensate for the absence of the aromatic ring; however, the highly energetic and stringent mannose-binding pocket of wild-type FimH is largely maintained. The Y137A mutation, on the other hand, is the most detrimental to FimH affinity and specificity: (i) in the absence of ligand the FimH C-terminal residue Thr158 intrudes into the mannose-binding pocket and (ii) ethylenediaminetetraacetic acid interacts strongly with Glu50, Thr53 and Asn136, in spite of multiple dialysis and purification steps. Upon mutation, pre-ligand-binding relaxation of the backbone dihedral angles at position 137 in the tyrosine gate and their coupling to Tyr48viathe interiorly located Ile52 form the basis of the loss of affinity of the FimH adhesin in the Y137A mutant.
authors.affiliation: Institute of Molecular Pharmacy, Pharmacenter, University of Basel , Klingelbergstrasse 50-70, CH-4056 Basel, Switzerland.
authors.forename: Said
authors.initials: S
authors.lastname: Rabbani
authors.affiliation: University of Lille, CNRS UMR8576 UGSF (Unité de Glycobiologie Structurale et Fonctionnelle), 59000 Lille, France; Structure et Fonction des Membranes Biologiques, Université Libre de Bruxelles (ULB), Brussels, Belgium.
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Krammer
authors.affiliation: University of Lille, CNRS UMR8576 UGSF (Unité de Glycobiologie Structurale et Fonctionnelle), 59000 Lille, France; Structure et Fonction des Membranes Biologiques, Université Libre de Bruxelles (ULB), Brussels, Belgium.
authors.forename: Goedele
authors.initials: G
authors.lastname: Roos
authors.affiliation: Institute of Molecular Pharmacy, Pharmacenter, University of Basel , Klingelbergstrasse 50-70, CH-4056 Basel, Switzerland.
authors.forename: Adam
authors.initials: A
authors.lastname: Zalewski
authors.affiliation: Institute of Molecular Pharmacy, Pharmacenter, University of Basel , Klingelbergstrasse 50-70, CH-4056 Basel, Switzerland.
authors.forename: Roland
authors.initials: R
authors.lastname: Preston
authors.affiliation: Institute of Molecular Pharmacy, Pharmacenter, University of Basel , Klingelbergstrasse 50-70, CH-4056 Basel, Switzerland.
authors.forename: Sameh
authors.initials: S
authors.lastname: Eid
authors.affiliation: Institute of Molecular Pharmacy, Pharmacenter, University of Basel , Klingelbergstrasse 50-70, CH-4056 Basel, Switzerland.
authors.forename: Pascal
authors.initials: P
authors.lastname: Zihlmann
authors.affiliation: Structure et Fonction des Membranes Biologiques, Université Libre de Bruxelles (ULB) , Brussels, Belgium.
authors.forename: Martine
authors.initials: M
authors.lastname: Prévost
authors.affiliation: University of Lille, CNRS UMR8576 UGSF (Unité de Glycobiologie Structurale et Fonctionnelle) , 59000 Lille, France.
authors.forename: Marc F
authors.initials: MF
authors.lastname: Lensink
authors.affiliation: Synchrotron SOLEIL , l'Orme de Merisiers, Saint-Aubin BP48, Gif-sur-Yvette CEDEX, France.
authors.forename: Andrew
authors.initials: A
authors.lastname: Thompson
authors.affiliation: Institute of Molecular Pharmacy, Pharmacenter, University of Basel , Klingelbergstrasse 50-70, CH-4056 Basel, Switzerland.
authors.forename: Beat
authors.initials: B
authors.lastname: Ernst
authors.affiliation: University of Lille, CNRS UMR8576 UGSF (Unité de Glycobiologie Structurale et Fonctionnelle) , 59000 Lille, France.
authors.forename: Julie
authors.initials: J
authors.lastname: Bouckaert
keywords: Escherichia coli infection; FimH adhesin; X-ray crystallography; biphenyl mannose; crystals; heptyl mannose; molecular dynamics; molecular recognition; mutations; peptide torsions; protein structure; thermodynamics; tyrosine gate