Regulation of (p)ppGpp-metabolic activities of RelA, Rel and SpoT

严格反应是细菌的一种重要适应机制，在细菌毒力、入侵存活、耐药性和持久性等方面起着重要的调节作用。响应于各种应激刺激，严格响应蛋白RelA调节警报素核苷酸（p）ppGpp的细胞内浓度。RelA具有强的核糖体依赖性（p）ppGpp合成活性，其通过直接感测核糖体A位点中的脱酰化tRNA而被氨基酸饥饿激活。我们对关键RelA和其他严格反应蛋白的机制的结构方面的了解的缺乏阻碍了SR领域本身的进展以及用于控制SR的有效分子工具的开发。我们计划通过确定单独的RelA和与底物复合的RelA的X射线结构以及确定低温蛋白质的结构来解决这个空白。RelA与细菌核糖体复合的电子显微镜结构。此外，我们将提供一个动力学描述的RelA水解酶和合成酶的功能在严格的响应过程中的相互作用。总的来说，我们的研究结果将提供基本的和机制的过程中，RelA介导的严格的反应，通过生产（p）ppGpp。此外，我们的研究结果还将为设计新型抗菌药物以对抗日益增加的多药耐药致病菌的流行提供结构基础。

The stringent response is a central bacterial adaptation mechanism, which plays an important role in regulation of bacterial virulence, survival during host invasion, antibiotic resistance and persistence. In response to various stress stimuli, the stringent response protein RelA modulates the intracellular concentration of the alarmone nucleotides (p)ppGpp. RelA possesses a strong ribosome-dependent (p)ppGpp synthetic activity that is activated by amino acid starvation via direct sensing of the deacylated tRNA in the ribosomal A-site. The paucity of our understanding of the structural aspects of the mechanism of key RelA and other stringent response proteins is hampering the progress of the SR field itself as well as the development of efficient molecular tools for controlling the SR. We plan to address this void by determination of X-ray structures of RelA alone and in complex with substrates as well as determine cryo-electron microscopy structures of RelA in complex with the bacterial ribosome. Moreover, we will provide a kinetic description of the interplay of the RelA hydrolase and synthetase functions during the stringent response. Collectively our findings will provide fundamental and mechanistic in the process by which RelA mediates the stringent response via production of (p)ppGpp. Moreover, our findings will also provide a structural basis for the design of novel antimicrobial agents to combat the ever-increasing prevalence of multi-drug resistant pathogenic bacteria.