Fig. 3.

EMSA experiments quantitating the lower binding affinity of full-length rHrcA for the CIRCE operator compared to truncated rHrcA. (A) Representative EMSA in which active fractions of full-length and truncated rHrcA that had been purified with DNA affinity chromatography were incubated with a DNA probe containing the C. trachomatis dnaK promoter and its CIRCE operator (51). Full-length rHrcA was tested over a range of concentrations from 4 to 128 nM, while truncated rHrcA was tested at a lower concentration range, up to 1.6 nM, which was sufficient to produce an almost complete gel shift. The locations of the free and bound probes on the gel are marked. (B) Graphs showing quantification of the EMSA results over a range of rHrcA concentrations. Note the different scales for the x axes of the two graphs. The values shown are the mean of results of three independent experiments, and the error bars represent standard deviations.