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J Bacteriol. 1992 October; 174(20): 6685-6687

research-article

Two transcriptionally active OmpR mutants that do not require phosphorylation by EnvZ in an Escherichia coli cell-free system.

Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey at Rutgers, Piscataway 08854.

ABSTRACT

D55Q-T83A and D55Q-G94S, two pseudorevertants of the D55Q mutant OmpR, an Escherichia coli transcriptional activator, were isolated previously by R. Brissette, K. Tsung, and M. Inouye (J. Bacteriol. 173:3749-3755, 1991). These pseudorevertant OmpR proteins were purified and examined for their function as transcriptional activators in a cell-free system with an ompF DNA fragment. These proteins were transcriptionally active, even after acid treatment, whereas the wild-type OmpR was completely inactive after the same treatment. Phosphorylation of acid-treated wild-type OmpR with an EnvZ11 membrane fraction and ATP restored transcriptional activity, whereas the activities of the mutant OmpR proteins did not change after phosphorylation.