FIG. 3.

DNase I protection by H-NS at the ctx promoter. The top and bottom strands of the ctx promoter fragments were incubated with increasing amounts of purified H-NS (0.25, 0.5, 1, and 2 μM) and treated with DNase I. Regions protected from DNase I cleavage by H-NS are shown by black bars. The ToxT high-affinity site protected from DNase I cleavage (72) is shown by a gray bar. White boxes represent the seven repeats of the heptad sequence 5′-TTTTGAT-3′. Open rectangles to the right represent the positions of the −10 and −35 hexamers. In each gel, a G+A DNA sequencing ladder is shown. The numbering is relative to the transcription start site.