Interactions between ArgR and the gltBDF promoter region. A. The ArgR-binding sequences upstream of gltBDF (top two lines) compared to the symmetrical consensus ArgR-binding site . Matches to the consensus are underlined. W = A or T, and N = A, C, G or T. B. Gel mobility shift analysis of ArgR binding to the region -406 to +246 of glt DNA. L-arginine was present in the reactions, the gel and running buffer (see Methods). C. DNase I protection assay of the region -462 to +161 bp upstream of gltBDF, labelled at the -462 end of the partner strand. The first 4 lanes represent a sequencing ladder of the partner strand in this region. ArgR concentrations of 0, 3.13, 6.25, 12.5, and 25 nM were used, and 5 mM L-arginine was present.