Translational initiation factor eIF5 replaces eIF1 on the 40S ribosomal subunit to promote start-codon recognition.
Translational initiation factor eIF5 replaces eIF1 on the 40S ribosomal subunit to promote start-codon recognition.
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DOI：
10.7554/elife.39273
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发表时间：
2018-11-30
期刊：
影响因子：
7.7
通讯作者：
Ramakrishnan V
中科院分区：
文献类型：
--
作者：
Llácer JL;Hussain T;Saini AK;Nanda JS;Kaur S;Gordiyenko Y;Kumar R;Hinnebusch AG;Lorsch JR;Ramakrishnan V
在真核生物翻译起始过程中，AUG对mRNA的识别需要Met-tRNAi调节到“PIN”状态，而这种状态会被eIF1因子拮抗。eIF5是eIF2的GTPase激活蛋白（GAP），它还能促进AUG的严格选择，但其双重功能的分子基础尚不清楚。我们提出了酵母48S预起始复合物（PIC）的冷冻电镜（cryo-EM）重建，总分辨率为3.0 Å，其特征是eIF5的n端结构域（NTD）在eIF1空出的位置与40S亚基结合。eIF5与Met-tRNAi相互作用，并允许其更容易定向。eIF5- ntd /tRNAi相互作用中eIF5残基的替换影响了体内近同源的UUG密码子的起始，以及体外闭合/打开的PIC构象，这与野生型eIF5- ntd对密码子：反密码子双工的直接稳定一致。目前的结构揭示了eIF5在开始密码子选择中的关键作用的基础。
In eukaryotic translation initiation, AUG recognition of the mRNA requires accommodation of Met-tRNAi in a ‘PIN’ state, which is antagonized by the factor eIF1. eIF5 is a GTPase activating protein (GAP) of eIF2 that additionally promotes stringent AUG selection, but the molecular basis of its dual function was unknown. We present a cryo-electron microscopy (cryo-EM) reconstruction of a yeast 48S pre-initiation complex (PIC), at an overall resolution of 3.0 Å, featuring the N-terminal domain (NTD) of eIF5 bound to the 40S subunit at the location vacated by eIF1. eIF5 interacts with and allows a more accommodated orientation of Met-tRNAi. Substitutions of eIF5 residues involved in the eIF5-NTD/tRNAi interaction influenced initiation at near-cognate UUG codonsin vivo, and the closed/open PIC conformation in vitro, consistent with direct stabilization of the codon:anticodon duplex by the wild-type eIF5-NTD. The present structure reveals the basis for a key role of eIF5 in start-codon selection.