The quorum sensing negative regulators EsaR and ExpREcc' homologues within the LusR family, retain the ability to function as activators of transcription

Most LuxR homologues function as activators of transcription during the process of quorum sensing, but a few, including EsaR and ExpREcc, negatively impact gene expression. The LuxR-activated luxI promoter and LuxR binding site, the lux box, were used in artificial contexts to assess the potential for transcriptional activation and DNA binding by EsaR and ExpREcc. Although the acyl-homoserine lactone responsiveness of both proteins is the opposite of that shown by most LuxR family members, EsaR and ExpREcc have preserved the ability to interact with RNA polymerase and activate transcription despite their low affinity for the lux box DNA. [PUBLICATION ABSTRACT]