Mechanism of gene activation by the Escherichia coli positive regulator, OmpR: a mutant defective in transcriptional activation.

The OmpR protein is an activator specific for the E. coli ompC and ompF genes. This protein functions in a phosphorylation-dependent manner through a presumed interaction with RNA polymerase. In this study we isolated OmpR mutants which were suggested to be defective for transcriptional activation, but not for DNA binding. Two such mutants, that we isolated, have a single amino acid alteration at positions 131 [P131S], and 179 [P179L], respectively, of OmpR, comprising 239 amino acids. These altered amino acids in OmpR may be implicated, directly or indirectly, in the presumed RNA polymerase/OmpR interaction that is important for transcriptional activation.