Translation of the genetic code into proteins is realized through repetitions of synchronous translocation of messenger RNA (mRNA) and transfer RNAs (tRNA) through the ribosome. In eukaryotes translocation is ensured by elongation factor 2 (eEF2), which catalyses the process and actively contributes to its accuracy¹. Although numerous studies point to critical roles for both the conserved eukaryotic posttranslational modification diphthamide in eEF2 and tRNA modifications in supporting the accuracy of translocation, detailed molecular mechanisms describing their specific functions are poorly understood. Here we report a high-resolution X-ray structure of the eukaryotic 80S ribosome in a translocation-intermediate state containing mRNA, naturally modified eEF2 and tRNAs. The crystal structure reveals a network of stabilization of codon–anticodon interactions involving diphthamide¹ and the hypermodified nucleoside wybutosine at position 37 of phenylalanine tRNA, which is also known to enhance translation accuracy². The model demonstrates how the decoding centre releases a codon–anticodon duplex, allowing its movement on the ribosome, and emphasizes the function of eEF2 as a ‘pawl’ defining the directionality of translocation³. This model suggests how eukaryote-specific elements of the 80S ribosome, eEF2 and tRNAs undergo large-scale molecular reorganizations to ensure maintenance of the mRNA reading frame during the complex process of translocation.

遗传密码翻译成蛋白质是通过核糖体中信使 RNA (mRNA) 和转移 RNA (tRNA) 的重复同步易位来实现的。在真核生物中，延伸因子 2 (eEF2) 确保易位，它催化该过程并积极促进其准确性¹ 。尽管大量研究指出 eEF2 中保守的真核翻译后修饰二邻苯二甲酰胺和 tRNA 修饰在支持易位准确性方面发挥着关键作用，但描述其特定功能的详细分子机制却知之甚少。在这里，我们报告了易位中间状态的真核 80S 核糖体的高分辨率 X 射线结构，其中包含 mRNA、天然修饰的 eEF2 和 tRNA。晶体结构揭示了密码子-反密码子相互作用的稳定网络，涉及二苯丙胺¹和苯丙氨酸 tRNA 37 位的超修饰核苷威布托辛，众所周知，这也可以提高翻译准确性² 。该模型演示了解码中心如何释放密码子-反密码子双链体，使其在核糖体上移动，并强调了 eEF2 作为定义易位方向性的“爪”的功能³ 。该模型表明 80S 核糖体、eEF2 和 tRNA 的真核生物特异性元件如何进行大规模分子重组，以确保在复杂的易位过程中维持 mRNA 阅读框。