Structure of a hibernating 100S ribosome reveals an inactive conformation of the ribosomal protein S1
Structure of a hibernating 100S ribosome reveals an inactive conformation of the ribosomal protein S1
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DOI：
10.1038/s41564-018-0237-0
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发表时间：
2018-10-01
影响因子：
28.3
通讯作者：
Wilson, Daniel N.
中科院分区：
文献类型：
--
作者：
Beckert, Bertrand;Turk, Martin;Wilson, Daniel N.
为了在营养缺乏等应激条件下生存，细菌70 S核糖体二聚化形成冬眠的100 S颗粒（1）。在γ-变形菌中，如大肠杆菌，100 S的形成需要核糖体调节因子（RMF）和冬眠促进因子（HPF）（2-4）。在这里，我们提出了单粒子冷冻电子显微镜结构的冬眠70 S和100 S粒子分离的静止相E。大肠杆菌细胞，分别在3.0埃和7.9埃分辨率。结构揭示了HPF和RMF的结合位点以及脱酰化E位点转移RNA和核糖体蛋白bS 1的意外存在。HPF与E-tRNA的反密码子-茎-环相互作用，并封闭信使RNA以及A-和P-位点tRNA的结合位点。RMF促进bS 1的紧凑构象的稳定，其一起隔离16 S核糖体RNA（rRNA）的抗Shine-Dalgarno序列，从而抑制翻译起始。在二聚化界面处，uS 2的C-末端探测到了RNA相关颗粒的mRNA进入通道，从而表明二聚化通过阻断通道内mRNA的结合来灭活核糖体。背靠背的大肠杆菌100 S排列与之前在革兰氏阳性细菌中观察到的100 S颗粒不同（5-8），并揭示了bS 1在翻译调控中的独特作用。
To survive under conditions of stress, such as nutrient deprivation, bacterial 70S ribosomes dimerize to form hibernating 100S particles(1). In gamma-proteobacteria, such as Escherichia coli, 100S formation requires the ribosome modulation factor (RMF) and the hibernation promoting factor (HPF)(2-4). Here we present single-particle cryo-electron microscopy structures of hibernating 70S and 100S particles isolated from stationary-phase E. coli cells at 3.0 angstrom and 7.9 angstrom resolution, respectively. The structures reveal the binding sites for HPF and RMF as well as the unexpected presence of deacylated E-site transfer RNA and ribosomal protein bS1. HPF interacts with the anticodon-stem-loop of the E-tRNA and occludes the binding site for the messenger RNA as well as A- and P-site tRNAs. RMF facilitates stabilization of a compact conformation of bS1, which together sequester the anti-Shine-Dalgarno sequence of the 16S ribosomal RNA (rRNA), thereby inhibiting translation initiation. At the dimerization interface, the C-terminus of uS2 probes the mRNA entrance channel of the symmetry-related particle, thus suggesting that dimerization inactivates ribosomes by blocking the binding of mRNA within the channel. The back-to-back E.coli 100S arrangement is distinct from 100S particles observed previously in Grampositive bacteria(5-8), and reveals a unique role for bS1 in translation regulation.