在核糖体上激活延长因子SelB的GTPase路径
Niels Fischer1, Piotr Neumann2, Lars V Bock3
1Department of Structural Dynamics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany.
Nature
|November 15, 2016
概括
在细菌中,单半素 (Sec) 的结合依赖于特定的tRNA和SelB因子. -EM结构揭示了Sec-tRNASec的UGA编码器如何在翻译过程中触发SelB GTPase的激活.
科学领域:
- 分子生物学
- 结构生物学
- 生物化学
背景情况:
- 单半氨酸 (Sec) 是第21种氨基酸,通过细菌中的专门的tRNA (tRNASec) 和转化因子 (SelB) 结合起来.
- 当Sec-tRNASec与mRNA干环结构相邻时,它会重新编码UGA停止,通常会终止翻译.
研究的目的:
- 阐明大肠杆菌中Sec-tRNASec重新编码的UGA编码体的结构机制.
- 了解 SelB 如何促进 Sec 插入,以及其 GTPase 活动如何在翻译过程中受到调节.
主要方法:
- 使用单粒子冷电子显微镜 (cryo-EM) 来确定六种关键中间体的结构.
- 在UGA重编程过程中分析了与核糖体结合的Sec-tRNASec和SelB复合体.
主要成果:
- 结构显示SelB对Sec-tRNASec的特定结合以及tRNA的大型结构变化.
- 核糖体经历了显著的重排,包括30S子单元的打开和关闭,以及Sec-tRNASec相对于素-素循环 (SRL) 的运动.
- 代识别触发了SelB对接到SRL,导致GTPase激活.
结论:
- 这项研究揭示了一种动态机制,即Sec-tRNASec结合和UGA编码的识别诱导了特定的核糖体构造变化.
- 这些结构重组对于将SelB招募到SRL并激活其GTPase功能至关重要,从而确保高效的类固醇结合.
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