Igo M M, Ninfa A J, Silhavy T J
Department of Biology, Princeton University, New Jersey 08544.
Genes Dev. 1989 May;3(5):598-605. doi: 10.1101/gad.3.5.598.
Transcription of the genes that encode the major outer membrane porin proteins OmpF and OmpC of Escherichia coli is regulated in response to changes in medium osmolarity by EnvZ and OmpR. EnvZ functions to sense environmental conditions and to relay this information to the DNA-binding protein OmpR. We have used a truncated EnvZ protein (EnvZ115), which is defective in sensory function but able to communicate with OmpR, to study the biochemical interactions between these two proteins and their effects on transcription from the ompF promoter. We show that purified EnvZ115 can phosphorylate OmpR in the presence of ATP. In addition, EnvZ115 stimulates the ability of OmpR to activate ompF transcription in vitro. Using antibodies specific for EnvZ, we have purified the wild-type protein and have shown that it is also an OmpR kinase. These results provide a prokaryotic example of a transmembrane sensory protein that functions as a protein kinase and suggest a mechanism by which EnvZ communicates with OmpR in signal transduction.
大肠杆菌主要外膜孔蛋白OmpF和OmpC的编码基因转录受EnvZ和OmpR调控，以响应培养基渗透压的变化。EnvZ负责感知环境条件并将该信息传递给DNA结合蛋白OmpR。我们使用了一种截短的EnvZ蛋白（EnvZ115），其在传感功能上有缺陷，但能够与OmpR交流，以研究这两种蛋白之间的生化相互作用及其对ompF启动子转录的影响。我们发现，纯化的EnvZ115在ATP存在的情况下能够使OmpR磷酸化。此外，EnvZ115在体外刺激OmpR激活ompF转录的能力。利用针对EnvZ的特异性抗体，我们纯化了野生型蛋白，并证明它也是一种OmpR激酶。这些结果提供了一个跨膜传感蛋白作为蛋白激酶发挥作用的原核生物实例，并提示了EnvZ在信号转导中与OmpR交流的一种机制。
