FIG. 2.

Gel shift assays showing direct binding of purified LuxR to promoters of 3OC6-HSL-regulated genes in vitro. Experiments were performed as previously described (28, 37). Reaction mixtures contained 1 fmol of DNA, 6 μM 3OC6-HSL, and either no LuxR (−) or LuxR at a final concentration of 6.2 nM (+). DNA probes were generated by PCR amplification of promoter regions using the transcriptional fusion plasmids as templates. Probes are shown side by side to facilitate comparison, even though sizes are different. VF0090 is shown as an example of a promoter fragment that is not shifted by LuxR, and this serves as a negative control.