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The Lys-48 residue of superoxide reductase from Desulfoarculus baarsii is essential for guiding and binding superoxide to the enzyme's iron center. This residue is one of the closest charged residues to the sixth iron coordination site.

Superoxide reductase (SOR) is a metalloenzyme that catalyzes the reduction of O2(super -) to H2O2 and provides an antioxidant mechanism in some anaerobic and microaerophilic bacteria. The acido-basic and pH dependence of the redox properties of the active site of SOR from Desulfoarculus baarsii, both in the absence and presence of O2(super -) are examined.

The specific formation of MutY-DNA cross-links using thio-modified nucleotide 4-thiothymidine ((super 4s)T) incorporated adjacent to the OG is demonstrated. The successful identification of the cross-link using duplex could pave the way for future cross-linking experiments with substrate and product analogues, in addition to cross-linking at other sites and with other photoreactive nucleotides.