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首页> 外文期刊>Journal of Molecular Biology >Interactions of translational factor EF-G with the bacterial ribosome before and after mRNA translocation.
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Interactions of translational factor EF-G with the bacterial ribosome before and after mRNA translocation.

机译：mRNA易位前后翻译因子EF-G与细菌核糖体的相互作用。

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摘要

A conserved translation factor, known as EF-G in bacteria, promotes the translocation of tRNA and mRNA in the ribosome during protein synthesis. Here, EF-G.ribosome complexes in two intermediate states, before and after mRNA translocation, have been probed with hydroxyl radicals generated from free Fe(II)-EDTA. Before mRNA translocation and GTP hydrolysis, EF-G protected a limited set of nucleotides in both subunits of the ribosome from cleavage by hydroxyl radicals. In this state, an extensive set of nucleotides, in the platform and head domains of the 30S subunit and in the L7/L12 stalk region of the 50S subunit, became more exposed to hydroxyl radical attack, suggestive of conformational changes in these domains. Following mRNA translocation, EF-G protected a larger set of nucleotides (23S rRNA helices H43, H44, H89, and H95; 16S rRNA helices h5 and h15). No nucleotide with enhanced reactivity to hydroxyl radicals was detected in this latter state. Both before and after mRNA translocation, EF-G protected identical nucleotides in h5 and h15 of the 30S subunit. These results suggest that h5 and h15 may remain associated with EF-G during the dynamic course of the translocation mechanism. Nucleotides in H43 and H44 of the 50S subunit were protected only after translocation and GTP hydrolysis, suggesting that these helices interact dynamically with EF-G. The effects in H95 suggest that EF-G interacts weakly with H95 before mRNA translocation and strongly and more extensively with this helix following mRNA translocation.
机译：保守的翻译因子，在细菌中称为EF-G，在蛋白质合成过程中促进tRNA和mRNA在核糖体中的移位。在这里，EF-G。核糖体复合物处于两个中间状态，在mRNA易位之前和之后，已经用游离Fe（II）-EDTA产生的羟基自由基进行了探测。在mRNA易位和GTP水解之前，EF-G保护了核糖体两个亚基中有限的一组核苷酸免受羟基自由基的切割。在这种状态下，位于30S亚基的平台和头部结构域以及50S亚基的L7 / L12茎区域的大量核苷酸变得更容易受到羟基自由基的攻击，这提示这些结构域的构象变化。 mRNA易位后，EF-G保护了更大的核苷酸集（23S rRNA螺旋H43，H44，H89和H95; 16S rRNA螺旋h5和h15）。在后一种状态下未检测到对羟基自由基具有增强的反应性的核苷酸。在mRNA易位之前和之后，EF-G都可以保护30S亚基的h5和h15中相同的核苷酸。这些结果表明，h5和h15在移位机制的动态过程中可能仍与EF-G相关。 50S亚基的H43和H44中的核苷酸仅在易位和GTP水解后才受到保护，这表明这些螺旋与EF-G动态相互作用。 H95中的作用表明EF-G在mRNA易位之前与H95相互作用较弱，而在mRNA易位后此螺旋强烈且更广泛地相互作用。

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