FIG 3.

CpxR interacts with the scsA promoter at the predicted CpxR binding site. (A) DNase I footprinting analysis of the promoter region of scsABCD, performed on both end-labeled coding and noncoding strands. Purified and acetyl-phosphate-preincubated CpxR (CpxR-P), at the final concentrations of 0.5 and 1 μM, was added to the DNA fragments. Solid vertical lines on the right and sequences on the left indicate the CpxR-protected region. (B) β-Galactosidase activity of wild-type (W-t) and ΔcpxR strains carrying reporter plasmids in which expression of the lacZ gene was directed by the native scsABCD promoter (Pscs) or by the promoter harboring mutations at the CpxR-binding site (Pscs*). The activity was determined on overnight cultures grown in LB medium with 100 mM MES (pH 7.0). The data correspond to mean values from three independent experiments performed in duplicate. Error bars correspond to SDs. (C) DNase I footprinting analysis of the native (Pscs) or mutant (Pscs*) promoter regions performed on the noncoding strand. CpxR-P was added at the same final concentrations as in panel A. The predicted CpxR-protected region is shown with solid vertical lines.