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Issue 8, 2016

The virulence factor LecB varies in clinical isolates: consequences for ligand binding and drug discovery

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Abstract

P. aeruginosa causes a substantial number of nosocomial infections and is the leading cause of death of cystic fibrosis patients. This Gram-negative bacterium is highly resistant against antibiotics and further protects itself by forming a biofilm. Moreover, a high genomic variability among clinical isolates complicates therapy. Its lectin LecB is a virulence factor and necessary for adhesion and biofilm formation. We analyzed the sequence of LecB variants in a library of clinical isolates and demonstrate that it can serve as a marker for strain family classification. LecB from the highly virulent model strain PA14 presents 13% sequence divergence with LecB from the well characterized PAO1 strain. These differences might result in differing ligand binding specificities and ultimately in reduced efficacy of drugs directed towards LecB. Despite several amino acid variations at the carbohydrate binding site, glycan array analysis showed a comparable binding pattern for both variants. A common high affinity ligand could be identified and after its chemoenzymatic synthesis verified in a competitive binding assay: an N-glycan presenting two blood group O epitopes (H-type 2 antigen). Molecular modeling of the complex suggests a bivalent interaction of the ligand with the LecB tetramer by bridging two separate binding sites. This binding rationalizes the strong avidity (35 nM) of LecBPA14 to this human fucosylated N-glycan. Biochemical evaluation of a panel of glycan ligands revealed that LecBPA14 demonstrated higher glycan affinity compared to LecBPAO1 including the extraordinarily potent affinity of 70 nM towards the monovalent human antigen Lewisa. The structural basis of this unusual high affinity ligand binding for lectins was rationalized by solving the protein crystal structures of LecBPA14 with several glycans.

Graphical abstract: The virulence factor LecB varies in clinical isolates: consequences for ligand binding and drug discovery

Supplementary files

Article information


Submitted
15 Feb 2016
Accepted
05 May 2016
First published
11 May 2016

This article is Open Access
All publication charges for this article have been paid for by the Royal Society of Chemistry

Chem. Sci., 2016,7, 4990-5001
Article type
Edge Article

The virulence factor LecB varies in clinical isolates: consequences for ligand binding and drug discovery

R. Sommer, S. Wagner, A. Varrot, C. M. Nycholat, A. Khaledi, S. Häussler, J. C. Paulson, A. Imberty and A. Titz, Chem. Sci., 2016, 7, 4990 DOI: 10.1039/C6SC00696E

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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