Laboratoire de Biologie Structurale de la Cellule, BIOC, Ecole polytechnique, CNRS, Institut Polytechnique de Paris, 91128, Palaiseau, cedex, France.
Laboratoire de Chimie Moléculaire, LCM, Ecole polytechnique, CNRS, Institut Polytechnique de Paris, 91128, Palaiseau, cedex, France.
Commun Biol. 2020 Feb 6;3(1):58. doi: 10.1038/s42003-020-0780-0.
Archaeal translation initiation occurs within a macromolecular complex containing the small ribosomal subunit (30S) bound to mRNA, initiation factors aIF1, aIF1A and the ternary complex aIF2:GDPNP:Met-tRNA. Here, we determine the cryo-EM structure of a 30S:mRNA:aIF1A:aIF2:GTP:Met-tRNA complex from Pyrococcus abyssi at 3.2 Å resolution. It highlights archaeal features in ribosomal proteins and rRNA modifications. We find an aS21 protein, at the location of eS21 in eukaryotic ribosomes. Moreover, we identify an N-terminal extension of archaeal eL41 contacting the P site. We characterize 34 N-acetylcytidines distributed throughout 16S rRNA, likely contributing to hyperthermostability. Without aIF1, the 30S head is stabilized and initiator tRNA is tightly bound to the P site. A network of interactions involving tRNA, mRNA, rRNA modified nucleotides and C-terminal tails of uS9, uS13 and uS19 is observed. Universal features and domain-specific idiosyncrasies of translation initiation are discussed in light of ribosomal structures from representatives of each domain of life.
古菌翻译起始发生在一个包含与 mRNA 结合的小核糖体亚基 (30S) 的大分子复合物中，该复合物还含有起始因子 aIF1、aIF1A 和三元复合物 aIF2:GDPNP:Met-tRNA。在这里，我们在 3.2Å 分辨率下确定了来自 Pyrococcus abyssi 的 30S:mRNA:aIF1A:aIF2:GTP:Met-tRNA 复合物的冷冻电镜结构。它突出了核糖体蛋白和 rRNA 修饰中的古菌特征。我们发现了一种 aS21 蛋白，其位置与真核核糖体中的 eS21 相对应。此外，我们还鉴定了一个接触 P 位的古菌 eL41 的 N 端延伸。我们对分布在 16S rRNA 中的 34 个 N-乙酰胞嘧啶进行了特征分析，它们可能有助于超耐热性。没有 aIF1 的情况下，30S 头部稳定，起始 tRNA 紧密结合到 P 位。观察到涉及 tRNA、mRNA、rRNA 修饰核苷酸和 uS9、uS13 和 uS19 的 C 端尾巴的相互作用网络。根据来自生命各领域的核糖体结构，讨论了翻译起始的普遍特征和域特异性特征。
