IscR acts as an activator in response to oxidative stress for the suf operon encoding Fe‐S assembly proteins

摘要: In Escherichia coli, Fe-S clusters are assembled by gene products encoded from the isc and suf operons. Both iscRSUA sufABCDSE operons induced highly oxidants, reflecting an increased need for providing maintaining under oxidative stress conditions. Three cis-acting oxidant-responsive elements (ORE-I, II, III) in upstream of sufA promoter serve as binding sites OxyR, IHF uncharacterized factor respectively. Using DNA affinity fractionation, we isolated ORE-III-binding that positively regulates operon response to various oxidants. MALDI-TOF mass analysis identified it with IscR, known a repressor expression anaerobic condition [2Fe-2S]-bound form. The iscR null mutation abolished activity cell extracts, caused significant decrease oxidant induction vivo. OxyR IscR contributed almost equally activate Purified lacked cluster bound ORE-III site activated transcription vitro. Mutations Fe-S-binding enabled activation vivo These results support model its demetallated form directly activates transcription, while de-represses operon, condition.