Department of Biochemistry, Emory University School of Medicine, Atlanta, United States.
Department of Chemistry, Columbia University, New York, United States.
Elife. 2020 Oct 5;9:e51898. doi: 10.7554/eLife.51898.
Modifications in the tRNA anticodon loop, adjacent to the three-nucleotide anticodon, influence translation fidelity by stabilizing the tRNA to allow for accurate reading of the mRNA genetic code. One example is the N1-methylguanosine modification at guanine nucleotide 37 (mG37) located in the anticodon loop andimmediately adjacent to the anticodon nucleotides 34, 35, 36. The absence of mG37 in tRNA causes +1 frameshifting on polynucleotide, slippery codons. Here, we report structures of the bacterial ribosome containing tRNA bound to either cognate or slippery codons to determine how the mG37 modification prevents mRNA frameshifting. The structures reveal that certain codon-anticodon contexts and the lack of mG37 destabilize interactions of tRNA with the P site of the ribosome, causing large conformational changes typically only seen during EF-G-mediated translocation of the mRNA-tRNA pairs. These studies provide molecular insights into how mG37 stabilizes the interactions of tRNA with the ribosome in the context of a slippery mRNA codon.
tRNA 反密码子环中的修饰，紧邻三碱基反密码子，通过稳定 tRNA 来影响翻译保真度，从而允许对 mRNA 遗传密码进行准确读取。一个例子是位于反密码子环中并紧邻反密码子核苷酸 34、35、36 的鸟嘌呤核苷酸 37 上的 N1-甲基鸟苷修饰（mG37）。tRNA 中 mG37 的缺失会导致多核苷酸上的 +1 移码，即滑码。在这里，我们报告了含有结合了同源或滑码的 tRNA 的细菌核糖体的结构，以确定 mG37 修饰如何防止 mRNA 移码。这些结构表明，某些密码子-反密码子环境和 mG37 的缺失会破坏 tRNA 与核糖体 P 位的相互作用，导致通常仅在 EF-G 介导的 mRNA-tRNA 对易位期间才可见的大构象变化。这些研究提供了分子见解，说明 mG37 如何在滑码 mRNA 环境中稳定 tRNA 与核糖体的相互作用。
