Conformational Differences between Open and Closed States of the Eukaryotic Translation Initiation Complex.
Conformational Differences between Open and Closed States of the Eukaryotic Translation Initiation Complex.
复制标题
DOI：
10.1016/j.molcel.2015.06.033
复制
发表时间：
2015-08-06
期刊：
影响因子：
16
通讯作者：
Ramakrishnan V
中科院分区：
文献类型：
--
作者：
Llácer JL;Hussain T;Marler L;Aitken CE;Thakur A;Lorsch JR;Hinnebusch AG;Ramakrishnan V
真核生物中的翻译起始始于包含40 S核糖体亚基、eIF 1、eIF 1A、eIF 3、三元复合物（eIF 2-GTP-Met-tRNAi）和eIF 5的前起始复合物（PIC）的形成。PIC以开放构象附着在mRNA的5′端，并扫描以定位起始密码子，然后关闭以阻止扫描。我们提出了单粒子冷冻电子显微镜（cryo-EM）重建48 S PIC从酵母在这些开放和封闭状态，在6.0 ℃和4.9 ℃，分别。这些重建显示了eIF 2 β以及eIF 3的构型，该构型似乎包围了40 S，占据了亚基界面的一部分。复合物的比较揭示了一个大的构象变化，在40 S头从一个开放的mRNA闩锁构象到一个封闭的，收缩的mRNA进入通道和缩小的P位点封闭的RNAi，从而阐明在起始密码子识别的关键事件。真核生物翻译起始复合物在开放和闭合状态下的结构在开放复合物中，40 S头向上移动以打开mRNA进入通道闩锁过渡到闭合状态将起始物tRNA锁定在与AUG碱基配对的P位点结构显示eIF 3如何在40 S亚基界面上接触eIF 2和eIF 1核糖体小亚基闩锁必须打开以允许mRNA装载。Llacer等人报告cryo-EM重建酵母翻译前起始复合物在开放和封闭的构象，突出结构差异和阐明起始密码子识别的关键事件。
Translation initiation in eukaryotes begins with the formation of a pre-initiation complex (PIC) containing the 40S ribosomal subunit, eIF1, eIF1A, eIF3, ternary complex (eIF2-GTP-Met-tRNAi), and eIF5. The PIC, in an open conformation, attaches to the 5′ end of the mRNA and scans to locate the start codon, whereupon it closes to arrest scanning. We present single particle cryo-electron microscopy (cryo-EM) reconstructions of 48S PICs from yeast in these open and closed states, at 6.0 Å and 4.9 Å, respectively. These reconstructions show eIF2β as well as a configuration of eIF3 that appears to encircle the 40S, occupying part of the subunit interface. Comparison of the complexes reveals a large conformational change in the 40S head from an open mRNA latch conformation to a closed one that constricts the mRNA entry channel and narrows the P site to enclose tRNAi, thus elucidating key events in start codon recognition. Structures of eukaryotic translation initiation complexes in open and closed states In the open complex the 40S head moves upward to open the mRNA entry channel latch Transition to closed state locks initiator tRNA in the P site base-paired with AUG The structures show how eIF3 contacts eIF2 and eIF1 on the 40S subunit interface The small ribosomal subunit latch has to open to allow mRNA loading. Llacer et al. report cryo-EM reconstructions of yeast translation pre-initiation complexes in both open and closed conformations, highlighting structural differences and elucidating key events in start codon recognition.