FIG. 3.

Analyses of ArgR binding to the oprD operator. (A) Gel retardation experiments. The radioactive ³²P-labeled oprD operator DNA (1 pM) was incubated with increasing concentrations of purified ArgR as indicated. (B) DNase I footprintings. The DNA fragment (100 pM) was specifically labeled at the 3′ end of each strand as described in Materials and Methods. Lanes 1 and 5, DNase I digestion in the absence of ArgR; lanes 2 and 6, 2.5 nM ArgR; lanes 3 and 7, 5 nM ArgR; lanes 4 and 8, 10 nM ArgR. The nucleotide sequence of the ArgR-protected region is indicated.