Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India.
Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore, 560064.
FEMS Microbiol Lett. 2018 Jul 1;365(13). doi: 10.1093/femsle/fny133.
During protein synthesis, elongation factor G (EFG) participates at the steps of translocation and ribosome recycling. Fusidic acid (FA) is a bacteriostatic antibiotic, which traps EFG on ribosomes, stalling them on mRNAs. How the bacterial susceptibility to FA is determined, and which of the two functions of EFG (translocation or ribosome recycling) is more vulnerable, has remained debatable. The in vivo studies addressing these aspects of FA mediated inhibition of protein synthesis are lacking. Here, we used a system of Escherichia coli strains and their complementation/supplementation with the plasmid borne copies of the inducible versions of EFG and ribosome recycling factor (RRF) genes. Additionally, we investigated FA sensitivity in a strain with increased proportion of stalled ribosomes. We show that the cells with high EFG/RRF (or low RRF/EFG) ratios are more susceptible to FA than those with low EFG/RRF (or high RRF/EFG) ratios. Our in vivo observations are consistent with the recent in vitro reports of dependence of FA susceptibility on EFG/RRF ratios, and the notion that an overriding target of FA is the translocation function of EFG. An applied outcome of our in vivo study is that FA mediated growth inhibition could be facilitated by depletion or inactivation of cellular RRF.
在蛋白质合成过程中，伸长因子 G（EFG）参与移位和核糖体循环这两个步骤。福沙酸（FA）是一种抑菌性抗生素，它可以将 EFG 固定在核糖体上，使核糖体在 mRNA 上停滞。细菌对 FA 的敏感性是如何决定的，以及 EFG 的两个功能（移位或核糖体循环）哪个更容易受到影响，一直存在争议。关于 FA 介导的蛋白质合成抑制的这些方面的体内研究还很缺乏。在这里，我们使用了一个大肠杆菌菌株系统，并用可诱导的 EFG 和核糖体回收因子（RRF）基因的质粒载体制备了其互补/补充菌株。此外，我们还研究了具有更多核糖体停滞比例的菌株对 FA 的敏感性。我们发现，EFG/RRF 比值高（或 RRF/EFG 比值低）的细胞比 EFG/RRF 比值低（或 RRF/EFG 比值高）的细胞对 FA 更敏感。我们的体内观察结果与最近关于 FA 敏感性依赖于 EFG/RRF 比值的体外报告以及 FA 的主要靶点是 EFG 的移位功能的观点一致。我们的体内研究的一个实际应用结果是，通过耗尽或失活细胞 RRF，可以促进 FA 介导的生长抑制。
