A Biophysical Study with Carbohydrate Derivatives Explains the Molecular Basis of Monosaccharide Selectivity of the Pseudomonas aeruginosa Lectin LecB

Abstract

The rise of resistances against antibiotics in bacteria is a major threat for public health and demands the development of novel antibacterial therapies. Infections with Pseudomonas aeruginosa are a severe problem for hospitalized patients and for patients suffering from cystic fibrosis. These bacteria can form biofilms and thereby increase their resistance towards antibiotics. The bacterial lectin LecB was shown to be necessary for biofilm formation and the inhibition with its carbohydrate ligands resulted in reduced amounts of biofilm. The natural ligands for LecB are glycosides of d-mannose and l-fucose, the latter displaying an unusual strong affinity. Interestingly, although mannosides are much weaker ligands for LecB, they do form an additional hydrogen bond with the protein in the crystal structure. To analyze the individual contributions of the methyl group in fucosides and the hydroxymethyl group in mannosides to the binding, we designed and synthesized derivatives of these saccharides. We report glycomimetic inhibitors that dissect the individual interactions of their saccharide precursors with LecB and give insight into the biophysics of binding by LecB. Furthermore, theoretical calculations supported by experimental thermodynamic data suggest a perturbed hydrogen bonding network for mannose derivatives as molecular basis for the selectivity of LecB for fucosides. Knowledge gained on the mode of interaction of LecB with its ligands at ambient conditions will be useful for future drug design.

Cinnamide Derivatives of d -Mannose as Inhibitors of the Bacterial Virulence Factor LecB from Pseudomonas aeruginosa

“…[25,27,28] However, we could show throughc hemical modification that this hydrogen bond does not have as ignificant influenceo nb inding affinity at ambient conditions in aqueous solution. [27,28] In our previouss tudy,w es ucceeded in obtainingaco-crystal structure of sulfonamide 2 in complex with LecB. In the absence of ac rystal structure for cinnamide 3 in complex with LecB, molecular dynamics simulations and NMR suggested an intercalation of the cinnamide residue into the beta-sandwich of the lectin.…”

“…Because in the crystal structure of LecB with d ‐mannose, a hydrogen bond between its 6‐OH and Ser23 was observed, particular attention was paid to this hydroxy group in the design of new inhibitors . However, we could show through chemical modification that this hydrogen bond does not have a significant influence on binding affinity at ambient conditions in aqueous solution . In our previous study, we succeeded in obtaining a co‐crystal structure of sulfonamide 2 in complex with LecB.…”

Development of a competitive binding assay for the Burkholderia cenocepacia lectin BC2L-A and structure activity relationship of natural and synthetic inhibitors

“…This series was previously generated to explain monosaccharide selectivity of the structurally related lectin LecB and dissect individual functional group contributions to the binding affinity. 27 For BC2L-A, only a weak affinity of L-fucose (5, IC50 498 µM) was detected and no inhibition by the methyl fucosides α-6 or β-7 was observed up to 666 µM. Removal of the glycosidic linkage of fucose in 8 or introduction of a C-methyl substituent in 9 also resulted in inactive compounds.…”

Bacterial Coaggregation Among the Most Commonly Isolated Bacteria From Contact Lens Cases

“…LecA has been shown to specifically bind to galactose or glucose, while LecB binds specifically to fucose or mannose. 38,39 In addition the type IV pili of P. aeruginosa can bind to the b-Nacetylgalactosamine (1-4)-b-galactose via the pilus subunit PilA. Staphylococcus aureus strains can produce various capsular polysaccharides that can coat their surface, and these capsules can contain N-acetylgalactosaminuronic acid, Nacetyl-D-fucosamine, N-acetyl-D-glucosaminuronic acid, and N-acetylmannosaminuronic acid, 40 which may represent the ligands for the P. aeruginosa protein(s).…”