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Structural basis for messenger RNA movement on the ribosome

机译:信使RNA在核糖体上运动的结构基础

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Translation initiation is a major determinant of the overall expression level of a gene(1 - 3). The translation of functionally active protein requires the messenger RNA to be positioned on the ribosome such that the start/ initiation codon will be read first and in the correct frame. Little is known about the molecular basis for the interaction of mRNA with the ribosome at different states of translation. Recent crystal structures of the ribosomal subunits(4 - 8), the empty 70S ribosome(9) and the 70S ribosome containing functional ligands(10 - 13) have provided information about the general organization of the ribosome and its functional centres. Here we compare the X- ray structures of eight ribosome complexes modelling the translation initiation, post- initiation and elongation states. In the initiation and post- initiation complexes, the presence of the Shine - Dalgarno ( SD) duplex causes strong anchoring of the 5' end of mRNA onto the platform of the 30S subunit, with numerous interactions between mRNA and the ribosome. Conversely, the 5' end of the ' elongator' mRNA lacking SD interactions is flexible, suggesting a different exit path for mRNA during elongation. After the initiation of translation, but while an SD interaction is still present, mRNA moves in the 3' -->5' direction with simultaneous clockwise rotation and lengthening of the SD duplex, bringing it into contact with ribosomal protein S2.
机译:翻译起始是基因总体表达水平的主要决定因素(1-3)。功能活性蛋白的翻译需要将信使RNA定位在核糖体上,这样才能首先以正确的框架读取起始/起始密码子。关于在不同翻译状态下mRNA与核糖体相互作用的分子基础知之甚少。核糖体亚基(4-8),空的70S核糖体(9)和含有功能性配体(10-13)的70S核糖体的最新晶体结构提供了有关核糖体及其功能中心的一般组织的信息。在这里,我们比较了八个核糖体复合物的X射线结构,它们模拟了翻译起始,起始后和延伸状态。在起始和起始后复合物中,Shine-Dalgarno(SD)双链体的存在会导致mRNA的5'末端牢固锚定在30S亚基的平台上,并且在mRNA和核糖体之间存在许多相互作用。相反,缺乏SD相互作用的“延伸子” mRNA的5'末端具有柔性,这表明在延伸过程中mRNA的退出路径不同。起始翻译后,但仍存在SD相互作用时,mRNA沿3'-> 5'方向移动,同时顺时针旋转并延长了SD双链体,使其与核糖体蛋白S2接触。

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