SoxR belongs to the MerR family of transcriptional regulators and is a sensor for the superoxide anion (O2) that is generated, for example, by redox-cycling compounds such as methyl viologen (paraquat [PQ]). SoxR is activated by O2- dependent reversible one-electron oxidation of its iron-sulfur center (10, 12, 20). Nitric oxide (NO) also activates SoxR, however, by a different mechanism than that observed for O2. The NO-dependent activation takes place via nitrosylation of iron-sulfur centers with displacement of sulfide to form dinitrosyl-iron-dithiol(cysteine) complexes (9).
Both the active and the inactive forms of SoxR bind the target promoters, but only the active form stimulates transcription, probably by promoting an allosteric rearrangement of the SoxR-DNA complex that favors transcription initiation (22, 18, 21). Notably, SoxR activates the expression of a single gene, soxS, which encodes the global transcriptional activator SoxS (18).
SoxS has homology to the AraC/XylS family of regulators and activates expression of target genes by binding to their promoters and recruiting RNA polymerase (26) and/or by binding to their promoters after forming a complex with the polymerase (15, 28).
Thus the question is whether we can characterize the enzyme/DNA complex change via some microfluidic flow properties, electrical properties, or other chip-based signal.