Université de Toulouse, UPS, Laboratoire de Microbiologie et Génétique Moléculaires, F-31000 Toulouse and CNRS, LMGM, F-31000 Toulouse, France.
Nucleic Acids Res. 2010 Jun;38(11):3546-54. doi: 10.1093/nar/gkq097. Epub 2010 Feb 26.
Escherichia coli can survive extreme acid stress for several hours. The most efficient acid resistance system is based on glutamate decarboxylation by the GadA and GadB decarboxylases and the import of glutamate via the GadC membrane protein. The expression of the corresponding genes is controlled by GadE, the central activator of glutamate-dependent acid resistance (GDAR). We have previously shown by genetic approaches that as well as GadE, the response regulator of the Rcs system, RcsB is absolutely required for control of gadA/BC transcription. In the presence of GadE, basal activity of RcsB stimulates the expression of gadA/BC, whereas activation of RcsB leads to general repression of the gad genes. We report here the results of various in vitro assays that show RcsB to regulate by direct binding to the gadA promoter region. Furthermore, activation of gadA transcription requires a GAD box and binding of an RcsB/GadE heterodimer. In addition, we have identified an RcsB box, which lies just upstream of the -10 element of gadA promoter and is involved in repression of this operon.
大肠杆菌可以在极端酸性环境中存活数小时。最有效的抗酸系统基于谷氨酸脱羧酶 GadA 和 GadB 的谷氨酸脱羧作用，以及通过 GadC 膜蛋白导入谷氨酸。相应基因的表达受谷氨酸依赖性酸抗性（GDAR）的中央激活剂 GadE 控制。我们之前通过遗传方法表明，除了 GadE 外，Rcs 系统的响应调节剂 RcsB 对于 gadA/BC 转录的控制也是绝对必需的。在 GadE 存在的情况下，RcsB 的基本活性会刺激 gadA/BC 的表达，而 RcsB 的激活则导致 gad 基因的普遍抑制。我们在此报告了各种体外测定的结果，这些结果表明 RcsB 通过直接结合 gadA 启动子区域来调节。此外，gadA 转录的激活需要 GAD 盒和 RcsB/GadE 异二聚体的结合。此外，我们已经确定了一个 RcsB 盒，它位于 gadA 启动子的-10 元件上游，参与该操纵子的抑制。
