FIG. 3.

AbrBN55(ox) and AbrB display identical binding recognition and specificity. The results of DNase I protection assays (footprinting) of protein binding to the BS18 aptomer sequence are shown. The target DNA used was an 105-bp EcoRI-HindIII fragment labeled either on one strand at its EcoRI end (A) or on the opposite strand at the HindIII end (B). Lanes 1 to 3 contained 1, 0.6, and 0.2 mg of AbrBN55(ox)/ml, respectively; lanes 6 to 8 contained 1.5, 0.9, and 0.4 mg of AbrB/ml, respectively; and lanes 4, 5, 9, and 10 contained no binding protein. The Maxam-Gilbert purine (lane U) and pyrimidine (lane Y) sequencing ladders for each fragment are shown for reference. DNase I footprinting assays were performed at 20°C essentially as described previously (16). Radiolabeled DNAs were prepared as described previously (16).