Fig. 4.

Superoxide dismutase (SOD). (A) The reaction catalyzed by SOD. (B) NiSOD structure and active site. The homohexameric structure of NiSOD (cartoon view, PDB access code 1t6u, Streptomyces coelicolor) is shown with each subunit a different color. One active site is shown in the oxidized form, with Ni³⁺ (green sphere) coordinated via the amino terminal amine, a backbone amide, two Cys, and an axial His (stick view). The His is displaced as a ligand for the reduced state (indicated by the dashed line).

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