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Science:核糖体生产蛋白质的关键因子

2015-10-08 13:38  
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Science:核糖体生产蛋白质的关键因子

在所有的活细胞中,DNA转录为RNA,然后RNA翻译成蛋白质。将RNA上的信息翻译为蛋白质的分子工厂被称为“核糖体”(在所附的影片显示)。这是一个庞大而复杂的实体,由RNA和蛋白质组成。

采用一种新的方法,耶鲁大学分子生物物理与生物化学系诺贝尔得奖主托马斯·施泰茨实验室的研究人员描述了,与称为延长因子4(EF4/LepA,图中为深蓝色)的新蛋白结合的核糖体的晶体结构,该蛋白在蛋白质的生产中发挥一个重要和迄今未知的作用。蛋白质的生产是所有生命中必不可少的过程。

该结构的获得新揭示了生产蛋白质的复杂过程,以及为创造更专门的药物铺平了道路。相关文章发表于2014年8月8日的《science》杂志上。

原文摘要:

Crystal structure of elongation factor 4 bound to a clockwise ratcheted ribosome

Matthieu G. Gagnon, Jinzhong Lin, David Bulkley, Thomas A. Steitz

Science 8 August 2014:
vol. 345 no. 6197 684-687

Elongation factor 4 (EF4/LepA) is a highly conserved guanosine triphosphatase translation factor. It was shown to promote back-translocation of tRNAs on posttranslocational ribosome complexes and to compete with elongation factor G for interaction with pretranslocational ribosomes, inhibiting the elongation phase of protein synthesis. Here, we report a crystal structure of EF4–guanosine diphosphate bound to the Thermus thermophilus ribosome with a P-site tRNA at 2.9 angstroms resolution. The C-terminal domain of EF4 reaches into the peptidyl transferase center and interacts with the acceptor stem of the peptidyl-tRNA in the P site. The ribosome is in an unusual state of ratcheting with the 30S subunit rotated clockwise relative to the 50S subunit, resulting in a remodeled decoding center. The structure is consistent with EF4 functioning either as a back-translocase or a ribosome sequester.

Fig. 1 The structure of EF4 bound to the ribosome.
(A) Overview of EF4, P-site tRNA (magenta), E-site tRNA (orange), and mRNA (light blue) bound to the 70S ribosome. The 50S and 30S subunits are shown in dark blue and yellow, respectively. (B) Illustration of EF4 shown in its ribosome-bound conformation. Each domain of EF4 is colored as in (A). (Insets) Two views of the unbiased Fobs – Fcalc difference Fourier map of the HTH of the CTD and the CCA-end of the P-site tRNA, with the attached phenylalanine residue contoured at 3σ obtained after initial refinement with an empty ribosome as a starting model.

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