• Non-Carbohydrate Glycomimetics as Inhibitors of Calcium(II)-Binding Lectins.

      Kuhaudomlarp, Sakonwan; Siebs, Eike; Shanina, Elena; Topin, Jérémie; Joachim, Ines; da Silva Figueiredo Celestino Gomes, Priscila; Varrot, Annabelle; Rognan, Didier; Rademacher, Christoph; Imberty, Anne; et al. (Wiley-VCH, 2021-03-03)
      Because of the antimicrobial resistance crisis, lectins are considered novel drug targets. Pseudomonas aeruginosa utilizes LecA and LecB in the infection process. Inhibition of both lectins with carbohydrate-derived molecules can reduce biofilm formation to restore antimicrobial susceptibility. Here, we focused on non-carbohydrate inhibitors for LecA to explore new avenues for lectin inhibition. From a screening cascade we obtained one experimentally confirmed hit, a catechol, belonging to the well-known PAINS compounds. Rigorous analyses validated electron-deficient catechols as millimolar LecA inhibitors. The first co-crystal structure of a non-carbohydrate inhibitor in complex with a bacterial lectin clearly demonstrates the catechol mimicking the binding of natural glycosides with LecA. Importantly, catechol 3 is the first non-carbohydrate lectin ligand that binds bacterial and mammalian calcium(II)-binding lectins, giving rise to this fundamentally new class of glycomimetics.
    • Protein-observed 19F NMR of LecA from Pseudomonas aeruginosa.

      Shanina, Elena; Siebs, Eike; Zhang, Hengxi; Silva, Daniel Varón; Joachim, Ines; Titz, Alexander; Rademacher, Christoph; HIPS, Helmholtz-Institut für Pharmazeutische Forschung Saarland, Universitätscampus E8.1 66123 Saarbrücken, Germany. (Oxford Academic, 2020-06-23)
      The carbohydrate-binding protein LecA (PA-IL) from Pseudomonas aeruginosa plays an important role in the formation of biofilms in chronic infections. Development of inhibitors to disrupt LecA-mediated biofilms is desired, but limited to carbohydrate-based ligands. Moreover, discovery of drug-like ligands for LecA is challenging due to its weak affinities. Therefore, we established a protein-observed 19F (PrOF) NMR to probe ligand binding to LecA. LecA was labeled with 5 - fluoroindole to incorporate 5 - fluorotryptophanes and the resonances were assigned by site-directed mutagenesis. This incorporation did not disrupt LecA preference for natural ligands, Ca2+ and d - galactose. Following NMR resonance perturbation of W42, which is located in the carbohydrate-binding region of LecA, allowed to monitor binding of low affinity ligands such as N - acetyl d - galactosamine (d - GalNAc, Kd = 780 ± 97 μM). Moreover, PrOF NMR titration with glycomimetic of LecA p-nitrophenyl β-d-galactoside (pNPGal, Kd = 54 ± 6 μM) demonstrated a six-fold improved binding of d - Gal proving this approach to be valuable for ligand design in future drug discovery campaigns that aim to generate inhibitors of LecA.