Binding of recombinant BldR to the promoter regions of Sso2536 and the mar-like operon. EMSAs of the −152/+10 region of the Sso2536 gene (A) and of the −271/+21 region of the mar-like operon (C) were performed both in the absence (lanes 2) and in the presence (lanes 3 to 6) of two different excess amounts of unlabeled unspecific (Sso10b coding sequence; lanes 3 and 4) or specific (lanes 5 and 6) DNAs, using 2 μM protein. The specificity of the binding was tested with three different protein amounts (5, 10, and 20 μM) on the S. solfataricus superoxide dismutase gene promoter (B, lanes 2, 3, and 4). Shown are the effects of increasing concentrations of benzaldehyde (D) or benzoic acid (E) on the mobility of the mar-like promoter with BldR. Lanes 2 to 9, 0.8 μM BldR and 0, 0.08, 0.16, 0.2, 0.4, 1.6, and 10 μM aromatic compounds. Similar results were obtained with the Sso2536 promoter. Lanes 1 in all panels indicate free labeled DNAs.