FIG. 4.

DNase footprinting assay of RNAP binding to uhpT promoter variants. Promoter fragments carrying the wild-type (WT), Δ22, and Nu35 sequences in the indicated absence or presence of 50 nM RNAP at 37°C for 30 min, followed by digestion with DNase I for 30 s at 25°C. The lanes marked A+G present the purine cleavage products from Maxam-Gilbert sequencing of the same fragment. The coordinates on the left of each panel are relative to the transcription start site of the wild-type promoter.