BACKGROUND From bacteria to eukarya, the specific recognition of the amino-acylated initiator tRNA by the universally conserved translational GTPase eIF5B/IF2 is one of the most central interactions in the process of translation initiation. However, the molecular details, particularly also in the context of ribosomal initiation complexes, are only partially understood. RESULTS A reinterpretation of the 6.6 Å resolution cryo-electron microscopy (cryo-EM) structure of the eukaryal 80S initiation complex using the recently published crystal structure of eIF5B reveals that domain IV of eIF5B forms extensive interaction interfaces with the Met-tRNAi, which, in contrast to the previous model, directly involve the methionylated 3' CCA-end of the acceptor stem. These contacts are mediated by a conserved surface area, which is homologous to the surface areas mediating the interactions between IF2 and fMet-tRNAfMet as well as between domain II of EF-Tu and amino-acylated elongator tRNAs. CONCLUSIONS The reported observations provide novel direct structural insight into the specific recognition of the methionylated acceptor stem by eIF5B domain IV and demonstrate its universality among eIF5B/IF2 orthologs in the three domains of life.

中文翻译：

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eSf5B在80S起始复合物中识别氨基酰化引发剂tRNA的结构见解。

背景技术从细菌到真核生物，普遍保守的翻译GTPase eIF5B / IF2对氨基酰化引发剂tRNA的特异性识别是翻译起始过程中最主要的相互作用之一。但是，分子的细节，特别是在核糖体起始复合物的背景下，仅被部分理解。结果使用最近发表的eIF5B晶体结构对真核80S起始复合物的6.6Å分辨率低温电子显微镜（cryo-EM）结构进行了重新解释，结果表明eIF5B的结构域IV与Met-tRNAi形成了广泛的相互作用界面，与以前的模型相比，直接涉及受体茎的甲硫酰化3'CCA末端。这些接触是由保守的表面积介导的，它与介导IF2和fMet-tRNAfMet之间以及EF-Tu的结构域II和氨基酰化的延伸剂tRNA之间相互作用的表面积同源。结论所报告的观察结果为eIF5B域IV对甲硫酰化受体茎的特异性识别提供了新颖的直接结构见解，并证明了其在生活的三个域中在eIF5B / IF2直系同源物中的普遍性。