Greenstein Andrew E, Hammel Michal, Cavazos Alexandra, Alber Tom
Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3220, USA.
J Biol Chem. 2009 Oct 23;284(43):29828-35. doi: 10.1074/jbc.M109.056168. Epub 2009 Aug 20.
An "environmental phosphatase" controls bacterial transcriptional responses through alternative sigma factor subunits of RNA polymerase and a partner switching mechanism has been proposed to mediate phosphatase regulation. In many bacteria, the environmental phosphatase and multiple regulators are encoded in separate genes whose products form transient complexes. In contrast, in the Mycobacterium tuberculosis homolog, Rv1364c, the phosphatase is fused to two characteristic regulatory modules with sequence similarities to anti-sigma factor kinases and anti-anti-sigma factor proteins. Here we exploit this fusion to explore interactions between the phosphatase and the regulatory domains. We show quantitatively that the anti-sigma factor kinase domain activates the phosphatase domain, the kinase-phosphatase fusion protein autophosphorylates in Escherichia coli, and phosphorylation is antagonized by the phosphatase activity. Small angle x-ray scattering defines solution structures consistent with the interdomain communication observed biochemically. Taken together, these data indicate that Rv1364c provides a single chain framework to understand the structure, function, and regulation of environmental phosphatases throughout the bacterial kingdom.
一种“环境磷酸酶”通过RNA聚合酶的替代σ因子亚基控制细菌转录反应，并且有人提出一种伴侣切换机制来介导磷酸酶调节。在许多细菌中，环境磷酸酶和多种调节因子由单独的基因编码，其产物形成瞬时复合物。相比之下，在结核分枝杆菌同源物Rv1364c中，磷酸酶与两个具有与抗σ因子激酶和抗抗σ因子蛋白序列相似性的特征性调节模块融合。在这里，我们利用这种融合来探索磷酸酶与调节结构域之间的相互作用。我们定量显示，抗σ因子激酶结构域激活磷酸酶结构域，激酶 - 磷酸酶融合蛋白在大肠杆菌中自磷酸化，并且磷酸化受到磷酸酶活性的拮抗。小角X射线散射确定的溶液结构与生化观察到的结构域间通讯一致。综上所述，这些数据表明Rv1364c提供了一个单链框架，以了解整个细菌界环境磷酸酶的结构、功能和调节。
