FIG. 1.

Interaction of VirB with the transcription regulatory region of the icsB virulence gene. DNase I footprinting was used to examine the interaction of purified VirB protein with the promoter-proximal (A) and promoter-distal (B) regions of the icsB upstream regulatory region (C). An angled arrow labeled +1 in panel C represents the transcription start site that was determined previously for icsB (42). The −10 and −35 hexamers of the promoter are shown in bold, as are the box 1 and 2 motifs. In panels A and B, white arrowheads indicate bands protected from DNase I digestion by VirB while black arrowheads indicate residues showing hypersensitivity to DNase I in the presence of VirB.