Fig 4.

EMSAs of the interaction of YkrK with various DNA probes. A ³²P-labeled DNA fragment containing the wild-type inverted repeat in the htpX promoter region and spanning from positions −77 to +97 (relative to the transcriptional initiation site of htpX) was used as the probe (probe I) in lanes 1 to 5. The same ³²P-labeled DNA fragment but containing a mutation in the left arm of the inverted repeat (GTTC to CAAG) was used as a control probe (probe II) in lanes 6 to 10. A ³²P-labeled DNA fragment containing a mutation in the right arm of the inverted repeat (AAC to TTG) was used as a second control probe (probe III) in lanes 11 to 15. About 1 nM ³²P-labeled DNA probe was used in each reaction mixture (final volume, 30 μl). Lanes 1, 6, and 11, DNA probe alone; lanes 2 to 5, 7 to 10, and 12 to 15, DNA probe plus increasing amounts of purified His-tagged YkrK (3, 6, 12, and 24 ng for each set of four lanes, respectively).