FIGURE 10.

The effect of OmpR mutants on β-galactosidase activity of ssrA-lacZ. OmpR wild type or mutants (listed below the relevant column) were expressed in an ompR null strain containing ssrA-lacZ in single copy (54). Overnight cultures were diluted 1:100 and grown to mid-log phase in LB media; IPTG was added to a final concentration of 1 mm and incubated for 2 h. Expression of mutant OmpR proteins was confirmed by a Western blot. Transcription of the ssrA-lacZ fusion was monitored by β-galactosidase assay as described previously (49). All β-galactosidase measurements were performed in triplicate with at least two independent cultures. The level of activity of wild type OmpR was set to 100%, and the mutants were expressed relative to it.