RNA polymerase activation mechanism by regulatory proteins

大肠杆菌主要外膜孔蛋白的表达。OmpC和OmpF在转录水平上受介质渗透压的调控。两个调节因子，OmpR和EnvZ，参与这种渗透调节。OmpR是细胞质激活蛋白，与ompC和ompF启动子中的识别序列结合。膜结合的EnvZ感知细胞外的渗透压，并表现出ompr特异性激酶和磷酸酶活性。envz介导的OmpR磷酸化激活了该蛋白，导致其与omp基因结合。与许多其他应答调节因子一样，239个氨基酸的OmpR由两个不同的结构域组成：OmpR的n端结构域包含一个磷酸化的位点，c端结构域显示出同源启动子特有的固有dna结合能力。对大肠杆菌基因组DNA序列的检查显示，至少有16种蛋白质的氨基酸序列与OmpR （OmpR蛋白家族）有广泛的相似性。与OmpR三级结构的氨基酸序列比对表明，所有这些家族蛋白都是通过保守的疏水残基相互作用折叠成类似的三级结构的。KdpE是ompr家族的成员之一，它参与膨胀压力的调节。其中一个具有识别KdpE启动子位点能力的突变蛋白被纯化并成功结晶。在光子工厂使用同步辐射收集衍射数据。

In Escherichia coli, expression of the major outer membrane porin proteins. OmpC and OmpF, is regulated at the transcriptional level in response to medium osmolarity. Two regulatory factors, OmpR and EnvZ, are involved in this osmoregulation. OmpR is the cytoplasmic activator protein, which binds to the recognition sequence in both ompC and ompF promoters. The membrane-bound EnvZ senses the osmolarity outside the cell and exhibits OmpR-specific kinase and phosphatase activity. EnvZ-mediated phosphorylation of OmpR activates the protein, which results in binding to the omp genes. As is the case for many other response regulators, the 239 amino acid OmpR consists of two distinct domains: the N-terminal domain of OmpR contains a site that is phosphorylated and the C-terminal domain exhibits an inherent DNA-binding ability specific to the cognate promoters. An inspection of the E.coli genome DNA sequences revealed that there are at least 16 proteins whose amino acid sequences show extensive similarities to that of OmpR (OmpR-family of proteins). An amino acid sequence alignment with the tertiary structure of OmpR in hand suggests that all these family proteins are folded into a similar tertiary structure by the interactions of the well conserved hydrophobic residues. KdpE is one of the members of the OmpR-family, which is involved in the regulation of turgor pressure. One of the mutant proteins which show the ability to recognize KdpE promoter sites was purified and was successfully crystallized. The diffraction data was collected using synchrotron radiation at the Photon Factory.