OxyR is a Key Regulator in Response to Oxidative Stress in

The role of the HO-sensing transcriptional regulator OxyR in oxidative stress responses in was investigated. An deletion mutant was more sensitive to HO and -butyl hydroperoxide than was the WT strain, indicating that OxyR mediates the defensive system against HO and organic peroxide. Evidence presented herein suggests that in cells treated with exogenous HO, the oxidized form of OxyR activated expression of by binding to a palindromic sequence of the promoter region. Oxidized OxyR also induced expression of other antioxidant enzymes (KatA1, KatA2, KatA3 and OhrB1) and oxidative stress regulators (CatR, OhrR and σ). The thiol-oxidative stress regulator gene was regulated at the transcription level by OxyR. We conclude that OxyR is necessary to activate transcription of from the σ-dependent promoter to express an unstable larger isoform of σ during oxidative stress. In response to oxidative stress, OxyR facilitates rapid production of HO-scavenging enzymes to repair oxidative damage through direct regulation and cascaded regulation of CatR, OhrR and σ.