Role of peroxide sensing transcription regulator OxyR in Streptomyces coelicolor

Abstract

Abstract

OxyR is an H2O2 sensing transcriptional regulator of the LysR-family that is generally found in Gram-negative bacteria and some Gram-positive bacteria. In Streptomyces coelicolor, OxyR positively regulates its own gene and ahpCD encoding alkyl hydro peroxidase. Another peroxide-sensing regulator CatR controls catalase A production in response to H2O2. It binds to catA and catR genes and represses their transcription. Physiological study showed that ΔoxyR mutant grew faster in liquid YEME (complex medium) and NMMP (minimal medium). On solid media, ΔoxyR mutant exhibited better growth and sporulation even when media contained various concentrations of H2O2. It was postulated that catA expression may be elevated in ΔoxyR mutant to allow better growth phenotype. The amount of catalase A was determined by activity staining and was found to be higher in the mutant. This suggests that compensatory catalase induction may have conferred ΔoxyR with the better growth phenotype. Moreover, antibiotic actinorhodin was produced more in ΔoxyR in both solid SFM and R2YE media and liquid minimal medium. To investigate the regulatory role of OxyR and CatR, their target genes need be unraveled on genome scale, possibly by chromatin immunoprecipitation (ChIP). As an initial step to perform ChIP analysis, tagging of OxyR and CatR with detectable probe was performed. Cloning of 6xMyc tag to the C-terminal end of OxyR and CatR were done. Specific detection of tagged proteins by anti-Myc antibody was successful. Further improvement of detection sensitivity, either by changing the tag or solubility optimization, will be useful for genome-wide detection of direct binding sites of OxyR and CatR. Key words: Streptomyces coelicolor, OxyR, catalase, CatR, myc tagging, oxidative stress, actinorhodin