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Coupling of Carbon and Nitrogen Regulation in Amino acid and Polyamine Catabolism through Two-component Regulatory Systems and A Novel Mechanism of Bacterial Catabolite Control

通过双组分调节系统耦合氨基酸和多胺分解代谢中的碳和氮调节以及细菌分解代谢物控制的新机制

基本信息

批准号：
14360060
负责人：
ITOH Yoshifumi
金额：
$ 7.87万
依托单位：
Akita Research Institute of Food and Brewing (2004)National Food Research Institute (2002-2003)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

Pseudomonas aeruginosa PAO1 utilizes histidine via a catabolic pathway encoded by the hutHUTIG operon as both carbon and nitrogen sources, and expression of this operon is regulated by both carbon and nitrogen. Succinate (the optimal carbon source and a catabolite repressor for this bacterium) partially suppressed expression of the hut operon (by about 25%). Ammonia (the optimal nitrogen source) alone had little effect on hut operon expression. However it powerfully (<5%) abrogated residual expression in the presence of succinate. The CbrA-CbrB and NtrB-NtrC two-component regulatory systems were essential for histidine utilization as a carbon source and as a nitrogen source, respectively. Succinate appeared to suppress hut operon transcription via the CbrA-CbrB system. On the contrary, the dicarboxylate seemed to enhance hut operon expression through the NtrB-NtrC system, allowing cells to use histidine as a nitrogen source. Ammonia (a nitrogen regulator) antagonized the NtrB-NtrC depe … More ndent activation of hut operon expression.A cbrB null mutant spontaneously produced a high frequency of revertants (about 10^<-5>), that restored the ability to utilize histidine as a carbon source. We isolated a revertant and identified a mutation (a C to T change at nt 251) in ntrC. In the revertant expression of the hut operon was no longer subjected to catabolite repression by succinate and to ammonia repression in the presence of succinate. The CbrB and NtrC response regulators are phosphorylated by cognate CbrA and NtrB proteins depending on carbon and nitrogen status, respectively, and serve as transcriptional activators. The NtrC251 protein having an amino acid substitution of Ala-84 to Val might have an altered structure that mimics the phosphorylated (active)status of the protein, resulting in constitutive expression of the hut operon. The absence of catabolite repression of the hut operon by succinate in the ntrC251 mutant supports the notion that modulation of CbrB phosphorylation levels is a crucial point in control of the hut operon by the catabolite repressor, succinate. Thus, the present study disclosed a novel mechanism of bacterial catabolite control, in which a two-component regulatory system is involved in sensing carbon status in the environment and modulating expression of a catabolic pathway. Less

铜绿假单胞菌PAO 1通过由hutHUTIG操纵子编码的分解代谢途径利用组氨酸作为碳源和氮源，并且该操纵子的表达受碳源和氮源的调节。琥珀酸盐（最佳碳源和该细菌的分解代谢物阻遏物）部分抑制hut操纵子的表达（约25%）。氨（最佳氮源）单独对hut操纵子表达的影响不大。然而，在琥珀酸存在下，它有力地（<5%）消除了残余表达。CbrA-CbrB和NtrB-NtrC双组分调控系统分别是组氨酸作为碳源和氮源利用所必需的。琥珀酸盐似乎通过CbrA-CbrB系统抑制hut操纵子转录。相反，二羧酸似乎通过NtrB-NtrC系统增强hut操纵子表达，允许细胞使用组氨酸作为氮源。氨（一种氮调节剂）拮抗NtrB-NtrC依赖， ...更多信息 cbrB无效突变体自发地产生高频率的回复突变体（约10 μ g<-5>），其恢复了利用组氨酸作为碳源的能力。我们分离了一个回复突变体并鉴定了ntrC中的一个突变（在nt 251处C变为T）。在回复突变体中，hut操纵子的表达不再受到琥珀酸盐的分解代谢物阻遏，并且在琥珀酸盐存在下不再受到氨阻遏。CbrB和NtrC反应调节剂分别根据碳和氮状态被同源CbrA和NtrB蛋白磷酸化，并充当转录激活剂。具有Ala-84至瓦尔的氨基酸取代的NtrC 251蛋白可能具有模拟蛋白的磷酸化（活性）状态的改变的结构，导致hut操纵子的组成型表达。在ntrC 251突变体中没有琥珀酸对hut操纵子的分解代谢物阻遏支持了这样的观点，即CbrB磷酸化水平的调节是分解代谢物阻遏物琥珀酸控制hut操纵子的关键点。因此，本研究揭示了一种新的细菌分解代谢物控制机制，其中双组分调节系统参与感知环境中的碳状态和调节分解代谢途径的表达。少