A Biophysical Study with Carbohydrate Derivatives Explains the Molecular Basis of Monosaccharide Selectivity of the Pseudomonas aeruginosa Lectin LecB
作者:Roman Sommer、Thomas E. Exner、Alexander Titz
DOI:10.1371/journal.pone.0112822
日期:——
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.
细菌对抗生素耐药性的增加是公共卫生的一大威胁,需要开发新型抗菌疗法。铜绿假单胞菌感染是住院病人和囊性纤维化患者面临的一个严重问题。这些细菌会形成生物膜,从而增加对抗生素的耐药性。研究表明,细菌凝集素 LecB 是生物膜形成的必要条件,使用其碳水化合物配体进行抑制可减少生物膜的数量。LecB 的天然配体是 d-甘露糖苷和 l-岩藻糖苷,后者显示出不同寻常的强亲和力。有趣的是,虽然甘露糖苷对 LecB 的配体作用要弱得多,但在晶体结构中,它们确实与蛋白质形成了额外的氢键。为了分析岩藻糖苷中的甲基和甘露糖苷中的羟甲基对结合的贡献,我们设计并合成了这些糖苷的衍生物。我们报告的仿糖抑制剂剖析了其糖类前体与 LecB 的单独相互作用,并深入揭示了 LecB 结合的生物物理学原理。此外,实验热力学数据支持的理论计算表明,甘露糖衍生物的氢键网络是 LecB 对岩藻糖苷具有选择性的分子基础。有关 LecB 与其配体在环境条件下的相互作用模式的知识将有助于未来的药物设计。