The stringent factor RelA adopts an open conformation on the ribosome to stimulate ppGpp synthesis.
The stringent factor RelA adopts an open conformation on the ribosome to stimulate ppGpp synthesis.
复制标题
DOI：
10.1093/nar/gkw470
复制
发表时间：
2016-07-27
影响因子：
14.9
通讯作者：
Wilson DN
中科院分区：
文献类型：
--
作者：
Arenz S;Abdelshahid M;Sohmen D;Payoe R;Starosta AL;Berninghausen O;Hauryliuk V;Beckmann R;Wilson DN
在应激条件下，如营养饥饿，核糖体A位点内结合的脱酰化tRNA被严格因子RelA识别，其将ATP和GTP/GDP转化为（p）ppGpp。信号分子（p）ppGpp全面重新连接细胞转录程序和一般代谢，导致应激适应。尽管严格响应对于细菌毒力、抗生素抗性和持久性的调节具有额外的重要性，但是缺乏对核糖体和脱酰基tRNA如何刺激RelA介导的（p）ppGpp的结构洞察。在这里，我们提出了一个cryo-EM结构的RelA在复杂的大肠杆菌70 S核糖体与平均分辨率为3.7 μ m和局部分辨率为4至>10 μ m的RelA。结构表明RelA采用独特的“开放”构象，其中C-末端结构域（CTD）在核糖体的亚基间空腔内缠绕在A/T样tRNA周围，N-末端结构域（NTD）延伸到溶剂中。我们认为，RelA在核糖体上的开放构象缓解了CTD对NTD的自抑制作用，从而导致RelA刺激（p）ppGpp合成。
Under stress conditions, such as nutrient starvation, deacylated tRNAs bound within the ribosomal A-site are recognized by the stringent factor RelA, which converts ATP and GTP/GDP to (p)ppGpp. The signaling molecules (p)ppGpp globally rewire the cellular transcriptional program and general metabolism, leading to stress adaptation. Despite the additional importance of the stringent response for regulation of bacterial virulence, antibiotic resistance and persistence, structural insight into how the ribosome and deacylated-tRNA stimulate RelA-mediated (p)ppGpp has been lacking. Here, we present a cryo-EM structure of RelA in complex with the Escherichia coli 70S ribosome with an average resolution of 3.7 Å and local resolution of 4 to >10 Å for RelA. The structure reveals that RelA adopts a unique ‘open’ conformation, where the C-terminal domain (CTD) is intertwined around an A/T-like tRNA within the intersubunit cavity of the ribosome and the N-terminal domain (NTD) extends into the solvent. We propose that the open conformation of RelA on the ribosome relieves the autoinhibitory effect of the CTD on the NTD, thus leading to stimulation of (p)ppGpp synthesis by RelA.