FIG. 3.
Specific binding of Fur to the dhb regulatory region. (A) The dhb promoter fragment (50 pM) was cut with AlwNI, end labeled, and incubated with native or EDTA-treated Fur. Lanes: 1, no Fur; 2, 10 nM Fur; 3, 10 nM EDTA-treated Fur. The positions of the unbound fur box and the shifted complex are indicated by unbound and bound, respectively. (B) The dhb promoter fragment (50 pM) was incubated with Fur for 10 min prior to the addition of cold competitor DNA. Lanes: 1, no Fur; 2, 10 nM Fur; 3, 10 nM Fur and 10 nM dhb competitor DNA; 4, 10 nM Fur and 100 nM dhb competitor DNA; 5, 10 nM Fur and 10 nM nonspecific competitor DNA; 6, 10 nM Fur and 100 nM nonspecific competitor DNA. The shifted complex is displaced only by the addition of the specific dhb competitor DNA.