FIG. 4.
DNase I protection of the bfpA (A) and perA (B) regulatory regions by MBP-PerA. Increasing amounts of MBP-PerA were mixed with 100,000 cpm of a 32P-end-labeled DNA fragment corresponding to positions −201 to +26 of bfpA and −155 to +81 of perA and treated with 0.003 U of DNase I. Samples were subjected to electrophoresis on an 8% polyacrylamide sequencing gel. The −35 promoter sequence and other upstream positions are indicated on the left; they were determined by running in parallel sequencing reactions with the same fragments (data not shown). The protected regions are indicated by vertical black bars. The black triangles above the gels represent increasing amounts of MBP-PerA. (A) Lanes: 1, DNA alone; 6 to 2, 159 nM, 316 nM, 634 nM, 1.26 μM, and 2.2 μM, respectively. (B) Lanes: 1, DNA alone; 7 to 2, 37 nM, 74 nM, 148 nM, 295 nM, 753 nM, and 1.5 μM, respectively.