• Lectin antagonists in infection, immunity, and inflammation.

      Meiers, Joscha; Siebs, Eike; Zahorska, Eva; Titz, Alexander; HIPS, Helmholtz-Institut für Pharmazeutische Forschung Saarland, Universitätscampus E8.1 66123 Saarbrücken, Germany. (Elsevier, 2019-08-27)
      Lectins are proteins found in all domains of life with a plethora of biological functions, especially in the infection process, immune response, and inflammation. Targeting these carbohydrate-binding proteins is challenged by the fact that usually low affinity interactions between lectin and glycoconjugate are observed. Nature often circumvents this process through multivalent display of ligand and lectin. Consequently, the vast majority of synthetic antagonists are multivalently displayed native carbohydrates. At the cost of disadvantageous pharmacokinetic properties and possibly a reduced selectivity for the target lectin, the molecules usually possess very high affinities to the respective lectin through ligand epitope avidity. Recent developments include the advent of glycomimetic or allosteric small molecule inhibitors for this important protein class and their use in chemical biology and drug research. This evolution has culminated in the transition of the small molecule GMI-1070 into clinical phase III. In this opinion article, an overview of the most important developments of lectin antagonists in the last two decades with a focus on the last five years is given
    • 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.