Bougdour Alexandre, Gottesman Susan
Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Proc Natl Acad Sci U S A. 2007 Jul 31;104(31):12896-901. doi: 10.1073/pnas.0705561104. Epub 2007 Jul 19.
IraP is a small protein that interferes with the delivery of sigma(S) (RpoS) to the ClpXP protease by blocking the action of RssB, an adaptor protein for sigma(S) degradation. IraP was previously shown to mediate stabilization of sigma(S) during phosphate starvation. Here, we show that iraP is transcribed in response to phosphate starvation; this response is mediated by ppGpp. The iraP promoter is positively regulated by ppGpp, dependent on the discriminator region of the iraP promoter. Sensing of phosphate starvation requires SpoT but not RelA. The results demonstrate a target for positive regulation by ppGpp and suggest that the cell use of ppGpp to mediate a variety of starvation responses operates in part by modulating sigma(S) levels.
IraP是一种小蛋白，它通过阻断RssB（一种用于σ(S)降解的接头蛋白）的作用，干扰σ(S)（RpoS）向ClpXP蛋白酶的传递。IraP先前已被证明在磷酸盐饥饿期间介导σ(S)的稳定。在这里，我们表明iraP是响应磷酸盐饥饿而转录的；这种反应由ppGpp介导。iraP启动子受到ppGpp的正调控，依赖于iraP启动子的鉴别区域。对磷酸盐饥饿的感知需要SpoT而不是RelA。结果证明了ppGpp正调控的一个靶点，并表明细胞利用ppGpp介导多种饥饿反应部分是通过调节σ(S)水平来实现的。
