Catalyzes the one-electron reduction of superoxide anion radical to hydrogen peroxide at a nonheme ferrous iron center. Plays a fundamental role in case of oxidative stress via its superoxide detoxification activity. 2 H(+) + reduced [rubredoxin] + superoxide = H2O2 + oxidized [rubredoxin] Binds 1 Fe(3+) ion per subunit. The iron ion 1 is coordinated via 4 cysteine residues. Binds 1 Fe(2+) ion per subunit. The iron ion 2 is coordinated via four histidines and one cysteine residue. E(0) is +2 mV for center I and +90 mV for center II at pH 7.5. Homodimer. Is organized in two protein domains. The N-terminal domain has a fold similar to that of desulforedoxin and contains a mononuclear Fe(3+) ion, center I. The second domain contains a different mononuclear iron center, center II, with a Fe(2+) ion. Catalysis occurs at center II. Fe(2+) ion of center II is the electron donor and is converted to the Fe(3+) form during the reaction. Belongs to the desulfoferrodoxin family. Was originally thought to be a rubredoxin oxidoreductase.