FIG 2.
EMSAs with purified Rex protein and DNA fragments from the promoter regions of predicted target genes in C. acetobutylicum. (A) DNA fragments (1 nM) from the promoter regions of C. acetobutylicum adhE2, ldh, crt, thlA, asrT, ptb, and nadA genes were fluorescence labeled and incubated with the indicated concentrations of Rex protein for 20 min at 30°C. Then, the protein-DNA complexes were resolved by electrophoresis on native 6% polyacrylamide gels. Quantification of the bands allowed the determination of the apparent Kd values (see Materials and Methods). The values shown represent the average and standard deviation of at least three independent assays. (B) As a negative control, the promoter region of the C. acetobutylicum pflBA operon, which lacks a putative Rex-binding site, was used.