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首页> 外文期刊>Journal of bacteriology >CitA/CitB Two-Component System Regulating Citrate Fermentation in Escherichia coli and Its Relation to the DcuS/DcuR System In Vivo
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CitA/CitB Two-Component System Regulating Citrate Fermentation in Escherichia coli and Its Relation to the DcuS/DcuR System In Vivo

机译：CitA / CitB两组分系统调节大肠杆菌中的柠檬酸发酵及其与DcuS / DcuR系统的体内关系

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Citrate fermentation by Escherichia coli requires the function of the citrate/succinate antiporter CitT (citT gene) and of citrate lyase (citCDEFXG genes). Earlier experiments suggested that the two-component system CitA/CitB, consisting of the membrane-bound sensor kinase CitA and the response regulator CitB, stimulates the expression of the genes in the presence of citrate, similarly to CitA/CitB of Klebsiella pneumoniae. In this study, the expression of a chromosomal citC-lacZ gene fusion was shown to depend on CitA/CitB and citrate. CitA/CitB is related to the DcuS/DcuR two-component system which induces the expression of genes for fumarate respiration in response to C4-dicarboxylates and citrate. Unlike DcuS, CitA required none of the cognate transporters (CitT, DcuB, or DcuC) for function, and the deletion of the corresponding genes showed no effect on the expression of citC-lacZ. The citAB operon is preceded by a DcuR binding site. Phosphorylated DcuR bound specifically to the promoter region, and the deletion of dcuS or dcuR reduced the expression of citC. The data indicate the presence of a regulatory cascade consisting of DcuS/DcuR modulating citAB expression (and CitA/CitB levels) and CitA/CitB controlling the expression of the citCDEFXGT gene cluster in response to citrate. In vivo fluorescence resonance energy transfer (FRET) and the bacterial two-hybrid system (BACTH) showed interaction between the DcuS and CitA proteins. However, BACTH and expression studies demonstrated the lack of interaction and cross-regulation between CitA and DcuR or DcuS and CitB. Therefore, there is only linear phosphoryl transfer (DcuS→DcuR and CitA→CitB) without cross-regulation between DcuS/DcuR and CitA/CitB.
机译：大肠杆菌发酵柠檬酸盐需要柠檬酸盐/琥珀酸逆转运蛋白CitT（ citT 基因）和柠檬酸裂解酶（ citCDEFXG 基因）的功能。较早的实验表明，由膜结合的传感器激酶CitA和响应调节剂CitB组成的两组分系统CitA / CitB可以在柠檬酸盐存在下刺激基因的表达，类似于肺炎克雷伯菌的CitA / CitB。在这项研究中，染色体 citC-lacZ 基因融合体的表达被证明依赖于CitA / CitB和柠檬酸盐。 CitA / CitB与DcuS / DcuR两组分系统有关，该系统诱导C 4 -二羧酸盐和柠檬酸盐诱导富马酸盐呼吸基因的表达。与DcuS不同，CitA不需要任何同源转运蛋白（CitT，DcuB或DcuC）即可发挥功能，相应基因的缺失对 citC-lacZ 的表达没有影响。 citAB 操纵子之前是DcuR结合位点。磷酸化的DcuR特异地结合到启动子区域， dcuS 或 dcuR 的缺失降低了 citC 的表达。数据表明存在由DcuS / DcuR调节 citAB 表达（和CitA / CitB水平）和控制 citCDEFXGT 基因簇表达的CitA / CitB组成的调节级联反应的存在。响应柠檬酸盐。体内荧光共振能量转移（FRET）和细菌双杂交系统（BACTH）显示了DcuS和CitA蛋白之间的相互作用。但是，BACTH和表达研究表明CitA和DcuR或DcuS和CitB之间缺乏相互作用和交叉调控。因此，只有线性磷酰基转移（DcuS→DcuR和CitA→CitB），而在DcuS / DcuR和CitA / CitB之间没有交叉调节。

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