Figure 5

Influence of LysP overproduction on CadC-mediated cadBA expression. Reporter gene assays were performed with E. coli EP314 (cadC::Tn10; cadA'::lacZ fusion) which was co-transformed with plasmid-encoded cadC or cadC_C208A,C272A and with a second plasmid carrying the lysP gene (pBAD33-lysP). Cells were cultivated under microaerobic conditions in minimal medium at pH 5.8 or pH 7.6 in the presence of 10 mM lysine at 37°C to mid-logarithmic growth phase, and harvested by centrifugation. When indicated, overproduction of LysP was induced by addition of 0.2% (w/v) arabinose. The activity of the reporter enzyme β-galactosidase was determined [43] and served as a measurement for cadBA expression. Shaded numbers display the degree of inhibition of cadBA expression by LysP overproduction. It should be noted that wild-type CadC activates cadBA expression only at pH 5.8. Error bars indicate standard deviations of the mean for at least three independent experiments.