Genetic Control of Nitrate Respiration in E. coli

肠杆菌如大肠杆菌和肠道沙门氏菌是兼性需氧菌，当培养 在没有氧气的情况下，可以使用多种替代呼吸氧化剂。硝酸盐和亚硝酸盐是 优选的替代物，并且厌氧呼吸酶基因表达响应于 他们的可用性。这种控制是由双重相互作用的两个组件的调节系统介导的。硝酸盐和 亚硝酸盐控制两种细胞质膜结合的传感器激酶，NarX和 NarQ蛋白，其反过来控制两种DNA结合反应调节剂NarL的磷酸化， 和NarP蛋白。因此，在超过一打操纵子的转录起始被激活或抑制 根据电子受体的可用性。Nar调控网络是肠杆菌所特有的;其他 变形菌的种类（包括几种人类病原体）仅含有NarQ-NarP系统（例如， 霍乱弧菌）或NarX-NarL系统（例如，铜绿假单胞菌）。因此，拟议的研究 广泛地告知我们对伽马和贝塔中许多物种的厌氧生理学的理解 变形菌的分支。这里提出的工作包括五个具体目标：（1）我们必须 在生物化学细节中表征体外交叉调节，以评估和扩展基于 主要是在体内观察。(2)与E.鲍德温，我们将研究合作DMA 由反应调节剂NarL结合。(3)与P. J.凯利合作，我们将研究转录 由反应调节剂NarP激活。(4)我们继续探索对定义的监管的回应 传感器NarX和NarQ发出的信号。(5)与M合作。M.伊果，我们会事先确认- 其表达受NarX-NarL或NarQ-NarP系统控制的未知靶基因。我们 总体目标是整合体内和体外方法，以更好地了解 无氧代谢这项基础研究与公共卫生的相关性是在以下领域： 无氧生理学和代谢。变形菌中的大多数致病菌是兼性的 需氧菌或兼性厌氧菌，许多感染性疾病涉及厌氧菌的定植。 环境，如哺乳动物的肠道。因此，从模式种E.大肠杆菌增强 了解对公共卫生有重大影响的广泛病原体。

Enterobacteria such as Escherichia coli and Salmonella enterica are facultative aerobes, and when cultured in the absence of oxygen can use a variety of alternative respiratory oxidants. Nitrate and nitrite are the preferred alternatives, and anaerobic respiratory enzyme gene expression is tightly controlled in response to their availability. This control is mediated by dual interacting two-component regulatory systems. Nitrate and nitrite control the autophosphorylation of two cytoplasmic membrane-bound sensor-kinases, the NarX and NarQ proteins, which in turn control the phosphorylation of two DNA-binding response regulators, the NarL and NarP proteins. Thus, transcription initiation at more than one dozen operons is activated or repressed according to electron acceptor availability. The Nar regulatory network is unique to enterobacteria; other species of proteobacteria (including several human pathogens) contain only the NarQ-NarP system (e.g., Vibrio cholerae) or the NarX-NarL system (e.g., Pseudomonas aeruginosa). The proposed studies therefore broadly inform our understanding of anaerobic physiology for many species within the gamma and beta subdivisions of the proteobacteria. Work proposed here comprises five specific aims: (1) We must characterize cross-regulation in vitro in biochemical detail in order to evaluate and extend models based primarily on in vivo observations. (2) In collaboration with E. P. Baldwin, we will study cooperative DMA binding by the response regulator NarL. (3) In collaboration with P. J. Kiley, we will study transcription activation by the response regulator NarP. (4) We continue to explore response to defined regulatory signals by the sensors NarX and NarQ. (5) In collaboration with M. M. Igo, we will identify previously- unknown target genes whose expression is controlled by the NarX-NarL or NarQ-NarP systems. Our overall goal is to integrate both in vivo and in vitro approaches to better understand the physiology of anaerobic metabolism. The relevance to public health of this fundamental research is in the realm of anaerobic physiology and metabolism. Most pathogenic species within the proteobacteria are facultative aerobes or facultative anaerobes, and many infectious diseases involve colonization of anaerobic environments such as the mammalian intestine. Thus, results from the model species E. coli enhance understanding for a broad range of pathogens that significantly impact public health.