Figure 6. Role of Position 4 base substituents in determining 933W repressor affinity for DNA.

(A) The base sequence at position 4 in one half site of the 933W binding site was changed as indicated. Dissociation constants were determined as described in Methods and Materials. (B) DNase I footprinting analysis of complexes between 933W repressor and 933W consensus sequence or its position 4 variants shown in (A) were performed as described in Methods and Materials. Shown is a Phosphoromager scan of the gel. The sequence of the operators are shown together with the positions of the bands resulting from DNase I cleavages in the absence (−) and presence (+) of saturating concentrations of 933W repressor.