Activation of the Vibrio vulnificus cadBA Operon by Leucine-responsive regulatory protein is mediated by CadC.

The present study revealed that Lrp, a leucine-responsive regulatory protein, is involved in the regulation of cadBA transcription through activation of PcadBA. The influence of Lrp on PcadBA was mediated by CadC, and thereby, CadC was able to compensate for the lack of Lrp in the activation of PcadBA. Western blot analyses and EMSA demonstrated that the cellular level of CadC was not significantly affected by Lrp, and that Lrp exerted its effect by directly binding to PcadBA. These combined results suggested that CadC and Lrp function cooperatively to activate the PcadBA rather than sequentially in a regulatory cascade.