GENETIC CONTROL OF NITRATE RESPIRATION IN E COLI

肠杆菌利用多种化合物作为末端电子受体 用于呼吸。氧气的使用优先于所有其他受体，并且 硝酸盐是首选的厌氧受体。分级监管 确保在体内合成适当的呼吸酶系统 对电子受体可获得性变化的反应。因此，在 厌氧生长，硝酸盐诱导甲酸脱氢酶-N合成和 硝酸还原酶，并抑制呼吸酶的合成 代谢不太受欢迎的电子受体，如亚硝酸盐和 富马酸。 这笔赠款支持的以前的工作已经确定了相互作用的两个 控制转录调控的成分调控系统 呼吸酶合成对硝酸盐的响应及其还原 产品，亚硝酸盐。双传感器(NARX和NARQ蛋白)监测 硝酸盐和亚硝酸盐的可用性，以及磷化或去磷化 相应地，双重反应调节因子(NARL和NARP蛋白)。 这项研究的长期目标是了解 这些平行的调控系统协调基因的表达 对硝酸盐和亚硝酸盐可用性的反应。顺位代理监管机构 NARL激活的Narg和fdnG操纵子的位置之前已经 特色化的。这项研究将描述顺式作用位点的特征 纳普激活的操纵子，AEG-46.5。与NARL激活的比较 调控序列将揭示DNA的相似和不同 由相应的反应调节因子NARL和NARP结合。突变 以及传感器NARX和NARQ的生化分析以及响应 监管机构NARL和NARP将帮助定义传感器响应监管机构 积极的和消极的调节都涉及到相互作用。 此外，该分析还将探讨传感器对信号的识别 分子(硝酸盐和亚硝酸盐)和响应调节剂识别 特定的DNA结合序列。NARL和NARP蛋白将是 在体外分析了特定的蛋白质-DNA相互作用。 最后，我们将对硝酸盐和亚硝酸盐信号的生理机制进行剖析。 通过监测靶操纵子诱导或抑制的速度 对不同浓度和比例的信号分子的响应， 硝酸盐和亚硝酸盐。 总体而言，这项研究将促进我们对厌氧性疾病的理解 生理学和新陈代谢，以及细菌信号转导途径。

Enterobacteria use a variety of compounds as terminal electron acceptors for respiration. Oxygen is used in preference to all other acceptors, and nitrate is the preferred anaerobic acceptor. Hierarchical regulation ensures that appropriate respiratory enzyme systems are synthesized in response to changing availability of electron acceptors. Thus, during anaerobic growth, nitrate induces synthesis of formate dehydrogenase-N and nitrate reductase, and represses synthesis of respiratory enzymes that metabolize less preferred electron acceptors, such as nitrite and fumarate. Previous work supported by this grant has identified interacting two component regulatory systems that control transcriptional regulation of respiratory enzyme synthesis in response to nitrate and its reduction product, nitrite. Dual sensors (the NARX and NARQ proteins) monitor the availability of nitrate and nitrite, and phosphorylate or dephosphorylate dual response regulators (the NARL and NARP proteins) accordingly. The long-term objective of this research is to understand the action of these parallel regulatory systems to coordinate gene expression in response to nitrate and nitrite availability. The cis-acting regulatory sites for the NARL-activated narG and fdnG operons have been previously characterized. This research will characterize the cis-acting sites for a NARP-activated operon, aeg-46.5. Comparison with the NARL-activated regulatory sequences will reveal similarities and differences in DNA binding by the homologous response regulators, NARL and NARP. Mutational and biochemical analysis of the sensors NARX and NARQ, and of the response regulators NARL and NARP, will help define sensor-response regulator interactions involved in both positive and negative regulation. Additionally, this analysis will probe sensor recognition of signal molecules (nitrate and nitrite), and response regulator recognition of specific DNA binding sequences. The NARL and NARP proteins will be analyzed in vitro with respect to specific protein-DNA interactions. Finally, the physiology of nitrate and nitrite signaling will be dissected by monitoring the rate of target operon induction or repression in response to varying concentrations and ratios of the signal molecules, nitrate and nitrite. Overall, this research will advance our understanding of both anaerobic physiology and metabolism, and of bacterial signal transduction pathways.