Isolation of reductase for SoxR that governs an oxidative response regulon from Escherichia coli.

SoxR is a transcription factor triggered by oxidative stress in Escherichia coli. Recent evidence suggests that novel redox regulation couples oxidation state to promoter activation. We have isolated the reductase for SoxR in E. coli using an assay of NADPH- and SoxR-dependent cytochrome c reductase activity. When the purified protein was incubated in an anaerobic reaction mixture containing SoxR and NADPH, the reduction of [2Fe-2S] cluster of SoxR was observed by optical and EPR spectroscopy. Our results indicate that the purified protein serves as an NADPH-dependent reduction system for SoxR.