EnvZ-OmpR interaction and osmoregulation in Escherichia coli

被引:230
作者
Cai, SJ [1 ]
Inouye, M [1 ]
机构
[1] Robert Wood Johnson Med Sch, Dept Biochem, Piscataway, NJ 08854 USA
关键词
D O I
10.1074/jbc.M110715200
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
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.
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页码:24155 / 24161
页数:7
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