• Synthesis of mannoheptose derivatives and their evaluation as inhibitors of the lectin LecB from the opportunistic pathogen Pseudomonas aeruginosa.

      Hofmann, Anna; Sommer, Roman; Hauck, Dirk; Stifel, Julia; Göttker-Schnetmann, Inigo; Titz, Alexander; hemical Biology of Carbohydrates, Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), D-66123 Saarbrücken, Germany. (2015-05-05)
      Biofilm formation and chronic infections with Pseudomonas aeruginosa depend on lectins produced by the bacterium. The bacterial C-type lectin LecB binds to the two monosaccharides l-fucose and d-mannose and conjugates thereof. Previously, d-mannose derivatives with amide and sulfonamide substituents at C6 were reported as potent inhibitors of the bacterial lectin LecB and LecB-mediated bacterial surface adhesion. Because d-mannose establishes a hydrogen bond via its 6-OH group with Ser23 of LecB in the crystal structure and may be beneficial for binding affinity, we extended d-mannose and synthesized mannoheptoses bearing the free 6-OH group as well as amido and sulfonamido-substituents at C7. Two series of diastereomeric mannoheptoses were synthesized and the stereochemistry was determined by X-ray crystallography. The potency of the mannoheptoses as LecB inhibitors was assessed in a competitive binding assay. The data reveal a diastereoselectivity of LecB for (6S)-mannoheptose derivatives with increased activity over methyl α-d-mannoside.
    • Virtual Screening Against Carbohydrate-Binding Proteins: Evaluation and Application to Bacterial Burkholderia ambifaria Lectin.

      Dingjan, Tamir; Gillon, Émilie; Imberty, Anne; Pérez, Serge; Titz, Alexander; Ramsland, Paul A; Yuriev, Elizabeth; HIPS, Helmholtz-Institut für Pharmazeutische Forschung Saarland, Universitätscampus E8.1 66123 Saarbrücken, Germany. (American Chemical Society, 2018-09-24)
      Bacterial adhesion to human epithelia via lectins constitutes a therapeutic opportunity to prevent infection. Specifically, BambL (the lectin from Burkholderia ambifaria) is implicated in cystic fibrosis, where lectin-mediated bacterial adhesion to fucosylated lung epithelia is suspected to play an important role. We employed structure-based virtual screening to identify inhibitors of BambL-saccharide interaction with potential therapeutic value. To enable such discovery, a virtual screening protocol was iteratively developed via 194 retrospective screening protocols against 4 bacterial lectins (BambL, BC2L-A, FimH, and LecA) with known ligands. Specific attention was given to the rigorous evaluation of retrospective screening, including calculation of analytical errors for enrichment metrics. The developed virtual screening workflow used crystallographic constraints, pharmacophore filters, and a final manual selection step. The protocol was applied to BambL, predicting 15 active compounds from virtual libraries of approximately 7 million compounds. Experimental validation using fluorescence polarization confirmed micromolar inhibitory activity for two compounds, which were further characterized by isothermal titration calorimetry and surface plasmon resonance. Subsequent testing against LecB from Pseudomonas aeruginosa demonstrated binding specificity of one of the hit compounds. This report demonstrates the utility of virtual screening protocols, integrating ligand-based pharmacophore filtering and structure-based constraints, in the search for bacterial lectin inhibitors.
    • The virulence factor LecB varies in clinical isolates: consequences for ligand binding and drug discovery

      Sommer, Roman; Wagner, Stefanie; Varrot, Annabelle; Nycholat, Corwin M.; Khaledi, Ariane; Häussler, Susanne; Paulson, James C.; Imberty, Anne; Titz, Alexander (2016)