PDF(Pubmed)
Abstract：
Argyrins are a family of naturally produced octapeptides that display promising antimicrobial activity against Pseudomonas aeruginosa. Argyrin B (ArgB) has been shown to interact with an elongated form of the translation elongation factor G (EF-G), leading to the suggestion that argyrins inhibit protein synthesis by interfering with EF-G binding to the ribosome. Here, using a combination of cryo-electron microscopy (cryo-EM) and single-molecule fluorescence resonance energy transfer (smFRET), we demonstrate that rather than interfering with ribosome binding, ArgB rapidly and specifically binds EF-G on the ribosome to inhibit intermediate steps of the translocation mechanism. Our data support that ArgB inhibits conformational changes within EF-G after GTP hydrolysis required for translocation and factor dissociation, analogous to the mechanism of fusidic acid, a chemically distinct antibiotic that binds a different region of EF-G. These findings shed light on the mechanism of action of the argyrin-class antibiotics on protein synthesis as well as the nature and importance of rate-limiting, intramolecular conformational events within the EF-G-bound ribosome during late-steps of translocation.
摘要：
Argyrin是天然产生的八肽家族，对铜绿假单胞菌显示出有希望的抗微生物活性。已显示ArgyrinB（ArgB）与平移伸长因子G（EF-G）的细长形式相互作用，导致提示精氨酸通过干扰EF-G与核糖体的结合来抑制蛋白质合成。这里,使用冷冻电子显微镜（cryo-EM）和单分子荧光共振能量转移（smFRET）的组合，我们证明，而不是干扰核糖体结合，ArgB快速且特异性地结合核糖体上的EF-G以抑制易位机制的中间步骤。我们的数据支持ArgB抑制易位和因子解离所需的GTP水解后EF-G内的构象变化，类似于夫西地酸的机理，一种化学上不同的抗生素，结合EF-G的不同区域。这些发现揭示了argyrin类抗生素对蛋白质合成的作用机制以及限速的性质和重要性，在易位的后期步骤中，EF-G结合的核糖体内的分子内构象事件。
