Igo M M, Ninfa A J, Stock J B, Silhavy T J
Department of Molecular Biology, Princeton University, New Jersey 08544-1014.
Genes Dev. 1989 Nov;3(11):1725-34. doi: 10.1101/gad.3.11.1725.
Signal transduction in the bacterial Omp, Che, and Ntr systems involves the phosphorylation and dephosphorylation of response regulators (OmpR, CheY and CheB, NRI) that share a homologous domain. We show that in the Omp system, the transmembrane sensor EnvZ, catalyzes both the phosphorylation of OmpR and the dephosphorylation of OmpR-P. The phosphorylation reaction proceeds by a mechanism shared with the Ntr and Che kinases, NRII, and CheA. EnvZ can phosphorylate NRI and can stimulate transcription from the glnAp2 promoter, and similarly, CheA can phosphorylate OmpR and can stimulate transcription from the ompF promoter. OmpR-P formed by either CheA or EnvZ is much more stable than CheY-P and NRI-P, but is rapidly hydrolyzed to OmpR and Pi by EnvZ in the presence of ATP, ADP, or nonhydrolyzable analogs of ATP. Because EnvZ is normally a transmembrane receptor with a periplasmic sensory domain, our results suggest that the role of EnvZ may be to control the intracellular concentration of OmpR-P in response to environmental signals.
细菌的外膜蛋白（Omp）、趋化（Che）和氮调节（Ntr）系统中的信号转导涉及具有同源结构域的应答调节因子（OmpR、CheY和CheB、NRI）的磷酸化和去磷酸化。我们发现，在Omp系统中，跨膜传感器EnvZ催化OmpR的磷酸化以及OmpR-P的去磷酸化。磷酸化反应通过与Ntr激酶、NRII和CheA激酶相同的机制进行。EnvZ可以磷酸化NRI并能刺激glnAp2启动子的转录，同样地，CheA可以磷酸化OmpR并能刺激ompF启动子的转录。由CheA或EnvZ形成的OmpR-P比CheY-P和NRI-P稳定得多，但在ATP、ADP或ATP的不可水解类似物存在时，会被EnvZ迅速水解为OmpR和磷酸根离子（Pi）。由于EnvZ通常是具有周质传感结构域的跨膜受体，我们的结果表明，EnvZ的作用可能是响应环境信号来控制OmpR-P的细胞内浓度。
