Replacement of Mn(III) with Cu(II) in Bacillus stearothermophilus superoxide dismutase. Similarity of the active site to the zinc site of copper/zinc superoxide dismutase.

Copper(II) was substituted for manganese(III) in Bacillus stearothermophilus Mn-superoxide dismutase. The (EPR) spectrum of the Cu(II) is distinctly rhombic, overlapping that of Cu(II) replacing zinc in copper/zinc superoxide dismutase. The copper-cyanide complex of the bacterial enzyme gives an EPR spectrum nearly identical to the cyanide-copper complex of the Cu/Zn enzyme, indicating three nitrogens as metal ligands. These results support the suggestion that metal coordination in B. stearothermophilus Mn-dismutase is a tetrahedral arrangement of three imidazoles and a carboxylate group and indicate copper as a good spectroscopic probe for studying the active site of Mn- and Fe-superoxide dismutases.