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  • Title: Osmoregulatory expression of the porin genes in Escherichia coli: evidence for signal titration in the signal transduction through EnvZ-OmpR phosphotransfer.
    Author: Nakashima K, Kanamaru K, Aiba H, Mizuno T.
    Journal: FEMS Microbiol Lett; 1991 Jul 15; 66(1):43-7. PubMed ID: 1657696.
    Abstract:
    The OmpR protein of Escherichia coli is a positive regulator specific for the ompF and ompC genes. The function of OmpR is modulated through phosphotransfer signaling mediated by the kinase, EnvZ. We previously demonstrated that OmpR contains two functional domains, which are physically separable; one is responsible for the interaction with EnvZ, whereas the other participates in interactions with cognate promoter DNAs. In this study, these domains of OmpR were overproduced in wild-type cells harboring the endogenous intact ompR gene on their chromosome. It was found that when the N-terminal domain of OmpR, which contains the phosphorylation site, was overproduced, expression of the ompF and ompC genes was markedly inhibited, irrespective of the osmolarity of the growth medium. Based on our current model for the molecular mechanism underlying signal transduction through Envz-OmpR phosphotransfer (T. Mizuno and S. Mizushima, Mol. Microbiol. 4, (1990), 1077-1082), we provide evidence that this phenomenon is best interpreted by the concept of 'signal titration' in the phosphotransfer signaling pathway.
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