FIG 7.
Effects of MgrB orthologs on E. coli PhoQ activity. (A) Sequence alignment of MgrB orthologs (*, fully conserved residues; :, conservation between strongly similar residues; ., conservation between weakly similar residues) . (B) β-Galactosidase levels of a ΔmgrB strain containing the PhoQ/PhoP-regulated transcriptional reporter PmgtA-lacZ (AML67) and also containing either an empty vector (pAL39), wild-type MgrB (pAL38), or a plasmid expressing the indicated MgrB orthologs. Inducer (IPTG) was not added, as leaky expression from the trc promoter resulted in sufficient levels of protein. Averages and standard deviations for the results of three independent experiments are shown. MU, Miller units. The statistical significances of changes in reporter activity were calculated with t tests by comparison to the wild type and are indicated with asterisks (***, P ≤ 0.001; **, P ≤ 0.01; ns, not significant). (C) GFP-MgrB expression for cells expressing MgrB orthologs was imaged by fluorescence microscopy, and GFP fluorescence levels were quantified (see Materials and Methods for details). The data represent averages and ranges for the results of two independent experiments comprised of 200 cells each, AU, arbitrary units.