A conformational switch in initiation factor 2 controls the fidelity of translation initiation in bacteria
A conformational switch in initiation factor 2 controls the fidelity of translation initiation in bacteria
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DOI：
10.1038/s41467-017-01492-6
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发表时间：
2017-11-14
影响因子：
16.6
通讯作者：
Gonzalez, Ruben L., Jr.
中科院分区：
文献类型：
--
作者：
Caban, Kelvin;Pavlov, Michael;Gonzalez, Ruben L., Jr.
起始因子 (IF) 2 通过选择性增加 50S 核糖体亚基与携带 N-甲酰基-甲硫氨酰-tRNA (fMet-tRNA(fMet)) 的 30S 起始复合物 (IC) 的连接速率来控制翻译起始的保真度。先前的研究表明，50S 亚基的快速连接涉及 GTP 和 fMet-tRNA (fMet) 依赖性的 IF2“激活”，但由于缺乏 30S IC 结合的 IF2 的结构和构象动力学数据，无法从机制上理解这一过程。在这里，使用 IF2-tRNA 单分子荧光共振能量转移信号，我们直接观察到缺乏 IF3 的 30S IC 中与 IF2 激活相关的构象转换。基于这些结果，我们提出了一个 IF2 激活模型，揭示了 GTP、fMet-tRNA(fMet) 和 IF2 的特定结构元件如何驱动和调节这种构象转换。值得注意的是，我们发现 IF2 的结构域 III 在 IF2 激活中发挥着关键的变构作用，这表明该结构域可以作为新型抗生素开发的目标。
Initiation factor (IF) 2 controls the fidelity of translation initiation by selectively increasing the rate of 50S ribosomal subunit joining to 30S initiation complexes (ICs) that carry an N-formyl-methionyl-tRNA (fMet-tRNA(fMet)). Previous studies suggest that rapid 50S subunit joining involves a GTP- and fMet-tRNA(fMet)-dependent "activation" of IF2, but a lack of data on the structure and conformational dynamics of 30S IC-bound IF2 has precluded a mechanistic understanding of this process. Here, using an IF2-tRNA single-molecule fluorescence resonance energy transfer signal, we directly observe the conformational switch that is associated with IF2 activation within 30S ICs that lack IF3. Based on these results, we propose a model of IF2 activation that reveals how GTP, fMet-tRNA(fMet), and specific structural elements of IF2 drive and regulate this conformational switch. Notably, we find that domain III of IF2 plays a pivotal, allosteric, role in IF2 activation, suggesting that this domain can be targeted for the development of novel antibiotics.