Activation of SoxR by overproduction of desulfoferrodoxin: Multiple ways to induce the soxRS regulon

The soxRS response, which protects cells against superoxide toxicity, is tr iggered by the oxidation of SoxR, a transcription factor. Superoxide excess and NADPH depletion induce the regulon. Unexpectedly, we found that the ov erproduction of desulfoferrodoxin, a superoxide reductase from sulfate-redu cing bacteria, also induced this response. We suggest that desulfoferrodoxi n interferes with the reducing pathway that keeps SoxR in its inactive form .