The CbrA-CbrB two-component regulatory system controls the utilization of multiple carbon and nitrogen sources in Pseudomonas aeruginosa
The CbrA-CbrB two-component regulatory system controls the utilization of multiple carbon and nitrogen sources in Pseudomonas aeruginosa
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DOI：
10.1046/j.1365-2958.2001.02435.x
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发表时间：
2001-05-01
影响因子：
3.6
通讯作者：
Itoh, Y
中科院分区：
文献类型：
--
作者：
Nishijyo, T;Haas, D;Itoh, Y
在铜绿假单胞菌中发现了一个新的双组分体系CbrA-CbrB；发现菌株PAO的cbrA和cbrB突变体不能使用几种氨基酸（如精氨酸、组氨酸和脯氨酸）、多胺和agmatine作为唯一的碳和氮源。这些突变体也不能利用或不能很好地利用许多其他碳源，包括甘露醇、葡萄糖、丙酮酸和柠檬酸。克隆并测序了一个携带cbrA和cbrB基因的7kb EcoRI片段。cbrA和cbrB基因分别编码传感器/组氨酸激酶（M-r 108 379, 983个残基）和同源反应调节因子（M-r 52 254, 478个残基）。根据12个可能的跨膜螺旋预测，CbrA的氨基末端（490个残基）似乎是一个传感膜结构域，而羧基末端部分与NtrB家族的组氨酸激酶具有同源性。CbrB反应监管机构显示出与NtrC家族成员的相似性。互补和引物延伸实验表明，cbrA和cbrB是从不同的启动子转录而来。在cbrA或cbrB突变体中，以及等位基因argR9901和argR9902突变体中，aot-argR操纵子不受精氨酸诱导，这表明该双组分系统在argr依赖的分解代谢途径的表达中发挥了重要作用，包括aruCFGDB操纵子指定主要的有氧精氨酸分解代谢途径。即使在存在组氨酸的情况下，组氨酸分解代谢酶在cbrAB突变体中也不表达，相反，负责脯氨酸利用的脯氨酸脱氢酶（Pru）在cbrB突变体中的表达水平与野生型菌株相当。当琥珀酸盐或其他c -4-二羧酸盐在1mm时加入脯氨酸培养基时，cbrB突变体恢复为Pru（+）表型。这种琥珀酸依赖的Pru（+）性质在20 mM氨水中几乎被消除。综上所述，CbrA-CbrB系统控制着几种分解代谢途径的表达，可能与NtrB-NtrC系统一起，似乎确保了铜绿假单胞菌细胞内碳氮平衡。
A novel two-component system, CbrA-CbrB, was discovered in Pseudomonas aeruginosa; cbrA and cbrB mutants of strain PAO were found to be unable to use several amino acids (such as arginine, histidine and proline), polyamines and agmatine as sole carbon and nitrogen sources. These mutants were also unable to use, or used poorly, many other carbon sources, including mannitol, glucose, pyruvate and citrate. A 7 kb EcoRI fragment carrying the cbrA and cbrB genes was cloned and sequenced. The cbrA and cbrB genes encode a sensor/histidine kinase (M-r 108 379, 983 residues) and a cognate response regulator (M-r 52 254, 478 residues) respectively. The amino-terminal half (490 residues) of CbrA appears to be a sensor membrane domain, as predicted by 12 possible transmembrane helices, whereas the carboxy-terminal part shares homology with the histidine kinases of the NtrB family. The CbrB response regulator shows similarity to the NtrC family members. Complementation and primer extension experiments indicated that cbrA and cbrB are transcribed from separate promoters. In cbrA or cbrB mutants, as well as in the allelic argR9901 and argR9902 mutants, the aot-argR operon was not induced by arginine, indicating an essential role for this two-component system in the expression of the ArgR-dependent catabolic pathways, including the aruCFGDB operon specifying the major aerobic arginine catabolic pathway. The histidine catabolic enzyme histidase was not expressed in cbrAB mutants, even in the presence of histidine, In contrast, proline dehydrogenase, responsible for proline utilization (Pru), was expressed in a cbrB mutant at a level comparable with that of the wild-type strain. When succinate or other C-4-dicarboxylates were added to proline medium at 1 mM, the cbrB mutant was restored to a Pru(+) phenotype. Such a succinate-dependent Pru(+) property was almost abolished by 20 mM ammonia. In conclusion, the CbrA-CbrB system controls the expression of several catabolic pathways and, perhaps together with the NtrB-NtrC system, appears to ensure the intracellular carbon: nitrogen balance in P. aeruginosa.