EnvZ-OmpR interaction and osmoregulation in Escherichia coli
EnvZ-OmpR interaction and osmoregulation in Escherichia coli
复制标题
DOI：
10.1074/jbc.m110715200
复制
发表时间：
2002-07-05
影响因子：
4.8
通讯作者：
Inouye, M
中科院分区：
文献类型：
--
作者：
Cai, SJ;Inouye, M
EnvZ是大肠杆菌中的一种组氨酸激酶/磷酸酶，它通过调节转录因子OmpR的磷酸化状态来响应培养基中的渗透压变化，从而控制外膜孔蛋白OmpF和OmpC的表达水平。虽然ompR和envZ基因都位于ompB基因座上，受ompB启动子控制，并转录为单一的多顺反子mRNA，但已知envZ的表达量明显低于ompR。然而，到目前为止，还没有对细胞中EnvZ和OmpR的数量进行准确的估计。本研究采用抗OmpR和抗envzc （EnvZ细胞质结构域）抗血清进行定量Western blot分析，检测野生型菌株MC4100中EnvZ和OmpR的水平。在L-broth培养基中观察到，在指数生长过程中，每细胞分别有3500和100分子的OmpR和EnvZ。高渗透压培养基（含20%蔗糖的营养液）培养的MC4100细胞的OmpR和EnvZ水平与l -肉汤培养的MC4100细胞基本相同，而低渗透压培养基（营养液）培养的MC4100细胞的OmpR和EnvZ水平是l -肉汤培养的MC4100细胞的1.7倍。利用His(10)- ompr，我们还确定了EnvZc-OmpR复合体地层的K-d值为1.20 +/- 0.17 mum。在此基础上，探讨了ompF和ompC渗透调节的分子机制。
EnvZ, a histidine kinase/phosphatase in Escherichia coli, responds to the osmolarity changes in the medium by regulating the phosphorylation state of the transcription factor OmpR, which controls the expression levels of outer membrane porin proteins OmpF and OmpC. Although both ompR and envZ genes are located on the ompB locus under the control of the ompB promoter and transcribed as a single polycistronic mRNA, the expression of envZ is known to be significantly less than ompR. However, to date no accurate estimation for the amounts of EnvZ and OmpR in the cell has been carried out. Here we examined the levels of EnvZ and OmpR in the wild-type strain MC4100 by quantitative Western blot analysis using anti-OmpR and anti-EnvZc (cytoplasmic domain of EnvZ) antisera. It was observed that during exponential growth in L-broth medium there were similar to3500 and 100 molecules per cell of OmpR and EnvZ, respectively. The levels of OmpR and EnvZ in MC4100 cells grown in a high osmolarity medium (nutrient broth with 20% sucrose) were about the same as those grown in L-broth, whereas they were 1.7-fold higher than those in a low osmolarity medium (nutrient broth). With His(10)-OmpR, we also determined that the K-d value for the EnvZc-OmpR complex formation is 1.20 +/- 0.17 mum. On the basis of these results, the molecular mechanism of osmoregulation of ompF and ompC is discussed.