β-Galactosidase expression of mutant <i>mrkA-lacZ</i> fusions in the MrkH^- (MC4100 + pACYC184) and MrkH⁺ (MC4100 + pMrkH) backgrounds.

<p>The double-base substitutions in the various operator mutants are shown below the MrkH box sequence. The β-galactosidase activity shown is the mean of results from three independent experiments, with standard deviations below 15%. The fold activation (fold act) is the value for the β-galactosidase activity of the MrkH⁺ strain divided by that of the MrkH⁻ strain. The fold activation for each mutant is also expressed as the percentage of that of the wild-type (% of WT).