Figure 4.

DNase I footprint of MotB on Pl₈ promoter DNA. The 5’-³²P labeled DNA surrounding the Pl₈ promoter (positions −143 to +75; 0.05 pmol DNA (10.9 pmol total bp), top labeled) was incubated with the indicated amount of MotB-His and treated with DNase I before electrophoresis on a 5% (w/v) polyacrylamide, 7 M urea denaturing gel. Footprints in (a,b) contain the same samples; however, for (b) samples were electrophoresed longer to better resolve the downstream region of the DNA. GA lanes represent G + A ladder. To the left of each gel, a schematic of the Pl₈ promoter region is shown with the T4 late promoter TATA box depicted in yellow and the +1-transcriptional start site indicated by the circular arrow head. Footprints are representative of two independent replicates. Nontemplate sequence (c) of the Pl₈ promoter (−143 to +75) with the TATA box highlighted in yellow, the 37 bp P8 oligo used for gel shift assays indicated by the dashed box, the +1-transcriptional start site indicated by the black arrow and larger font, and the +28 position indicated by the red arrow.