Streptomyces coelicolor Encodes a Urate-Responsive Transcriptional Regulator with Homology to PecS from Plant Pathogens

Many transcriptional regulators control gene activity by responding to specific ligands. Members of the multiple-antibiotic resistance regulator (MarR) family of transcriptional regulators feature prominently in this regard, and they frequently function as repressors in the absence of their cognate ligands. Plant pathogens such asDickeya dadantii encode a MarR homolog named PecS that controls expression of a gene encoding the efflux pump PecM in addition to other virulence genes. We report here that the soil bacteriumStreptomyces coelicolor also encodes a PecS homolog (SCO2647 ) that regulates apecM gene (SCO2646 ).S. coelicolor PecS, which exists as a homodimer, binds the intergenic region betweenpecS andpecM genes with high affinity. Several potential PecS binding sites were found in this intergenic region. The binding of PecS to its target DNA can be efficiently attenuated by the ligand urate, which also quenches the intrinsic fluorescence of PecS, indicating a direct interaction between urate and PecS.In vivo measurement of gene expression showed that activity ofpecS andpecM genes is significantly elevated after exposure ofS. coelicolor cultures to urate. These results indicate thatS. coelicolor PecS responds to the ligand urate by attenuated DNA bindingin vitro and upregulation of gene activityin vivo . Since production of urate is associated with generation of reactive oxygen species by xanthine dehydrogenase, we propose that PecS functions under conditions of oxidative stress.