Leonardo M R, Forst S
Department of Biological Sciences, University of Wisconsin, Milwaukee 53201, USA.
Mol Microbiol. 1996 Nov;22(3):405-13. doi: 10.1046/j.1365-2958.1996.1271487.x.
In Escherichia coli, EnvZ senses changes in the osmotic conditions of the growth environment and controls the phosphorylated state of the regulatory protein, OmpR. OmpR-phosphate regulates the expression of the porin genes, ompF and ompC. To investigate the role of the periplasmic domain of EnvZ in sensing of osmolarity signals, portions of this domain were deleted. Cells containing the EnvZ mutant proteins were able to regulate normally the production of OmpF and OmpC in response to changes in osmolarity. The periplasmic domain of EnvZ was also replaced with the non-homologous periplasmic domain of the histidine kinase PhoR of Bacillus subtilis. Osmoregulation of OmpF and OmpC production in cells containing the PhoR-EnvZ hybrid protein was indistinguishable from that in cells containing wild-type EnvZ. Identical results were obtained with an envZ-pta/ack strain, which could not synthesize acetyl phosphate. Thus, acetyl phosphate was not involved in the regulation of ompF and ompC observed in this study. These results indicate that the periplasmic domain of EnvZ is not essential for sensing of osmolarity signals.
在大肠杆菌中，EnvZ可感知生长环境渗透压条件的变化，并控制调节蛋白OmpR的磷酸化状态。磷酸化的OmpR调节孔蛋白基因ompF和ompC的表达。为了研究EnvZ周质结构域在渗透压信号感知中的作用，该结构域的部分区域被删除。含有EnvZ突变蛋白的细胞能够根据渗透压的变化正常调节OmpF和OmpC的产生。EnvZ的周质结构域也被枯草芽孢杆菌组氨酸激酶PhoR的非同源周质结构域所取代。含有PhoR-EnvZ杂合蛋白的细胞中OmpF和OmpC产生的渗透调节与含有野生型EnvZ的细胞中无法区分。使用不能合成乙酰磷酸的envZ-pta/ack菌株也获得了相同的结果。因此，乙酰磷酸不参与本研究中观察到的ompF和ompC的调节。这些结果表明，EnvZ的周质结构域对于渗透压信号的感知并非必不可少。
