FIG. 2.
Complexes formed by RNAP and the comG promoter with or without ComK present. Electrophoretic mobility shift assays were performed with a 200-bp 32P-labeled comG promoter fragment. RNAP concentrations were increased in twofold increments from 0 to 44 nM, as indicated by the concentration bars. The positions of the different complexes are shown on the right. K, ComK; R, RNAP; Fp, free probe. (A) RNAP binding in the absence of ComK. (B) RNAP binding in the presence of 0.35 μM ComK. For comparison, a blank sample (−) and binding of only RNAP (R; 22 nM) are shown in the first and second lanes, respectively. (C) The percentage of radioactive probe in the RNAP-promoter complex as determined by densitometric scanning was plotted against nanomoloar RNAP concentration. The percentage was calculated by dividing the signal of the RNAP band by the total signal in each lane, which was determined by combining the intensities of the bands present per lane. Triangles, no ComK present; squares, 0.35 μM ComK.