The Escherichia coli CpxA-CpxR envelope stress response system regulates expression of the Porins OmpF and OmpC
The Escherichia coli CpxA-CpxR envelope stress response system regulates expression of the Porins OmpF and OmpC
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DOI：
10.1128/jb.187.16.5723-5731.2005
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发表时间：
2005-08-01
影响因子：
3.2
通讯作者：
Goulian, M
中科院分区：
文献类型：
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作者：
Batchelor, E;Walthers, D;Goulian, M
我们对双色荧光报告菌株进行转座子诱变，以确定大肠杆菌中孔蛋白基因 ompF 和 ompC 的新调节因子。通过荧光显微镜对集落进行筛选，发现许多突变体表现出有趣的孔蛋白表达模式。一种突变体在编码组氨酸激酶 CpxA 的基因中插入了一个插入片段，CpxA 是响应包膜应激的双组分信号系统的传感器。在乙酰磷酸水平高的条件下，cpx,4突变体表现出ompC转录增加和ompF转录强烈减少。随后的遗传分析表明，这种表型依赖于反应调节剂 CpxR 的磷酸化，并且野生型细胞中 CpxA 的激活会导致孔蛋白表达的类似调节。使用 DNase I 足迹，我们证明 CpxR 结合 ompF 和 ompC 启动子的上游。因此，两个不同的双组分系统 CpxA-CpxR 和 EnvZ-OmpR 似乎在孔蛋白启动子处汇聚。在包膜应激的背景下，外膜 β-桶蛋白通常与 Sigma E 途径相关。然而，至少对于经典孔蛋白 OmpF 和 OmpC，我们的结果表明 Cpx 包膜应激反应系统在调节其表达中发挥作用。
We performed transposon mutagenesis of a two-color fluorescent reporter strain to identify new regulators of the porin genes ompF and ompC in Escherichia coli. Screening of colonies by fluorescence microscopy revealed numerous mutants that exhibited interesting patterns of porin expression. One mutant harbored an insertion in the gene encoding the histidine kinase CpxA, the sensor for a two-component signaling system that responds to envelope stress. The cpx,4 mutant exhibited increased transcription of ompC and a very strong decrease in transcription of ompF under conditions in which acetyl phosphate levels were high. Subsequent genetic analysis revealed that this phenotype is dependent on phosphorylation of the response regulator CpxR and that activation of CpxA in wild-type cells results in similar regulation of porin expression. Using DNase I footprinting, we demonstrated that CpxR binds upstream of both the ompF and ompC promoters. It thus appears that two distinct two-component systems, CpxA-CpxR and EnvZ-OmpR, converge at the porin promoters. Within the context of envelope stress, outer membrane beta-barrel proteins have generally been associated with the sigma E pathway. However, at least for the classical porins OmpF and OmpC, our results show that the Cpx envelope stress response system plays a role in regulating their expression.