Superoxide dismutases (SODs, EC 22.214.171.124) are ubiquitous enzymes that efficiently catalyze the dismutation of superoxide radical anions to protect biological molecules from oxidative damage. The crystal structure of nickel-containing SOD (NiSOD) from Streptomyces seoulensis was determined for the resting, x-ray-reduced, and thiosulfate-reduced enzyme state. NiSOD is a homohexamer consisting of four-helix-bundle subunits. The catalytic center resides in the N-terminal active-site loop, where a Ni(III) ion is coordinated by the amino group of His-1, the amide group of Cys-2, two thiolate groups of Cys-2 and Cys-6, and the imidazolate of His-1 as axial ligand that is lost in the chemically reduced state as well as after x-ray-induced reduction. This structure represents a third class of SODs concerning the catalytic metal species, subunit structure, and oligomeric organization. It adds a member to the small number of Ni-metalloenzymes and contributes with its Ni(III) active site to the general understanding of Ni-related biochemistry. NiSOD is shown to occur also in bacteria other than Streptomyces and is predicted to be present in some cyanobacteria.
Crystal structure of nickel-containing superoxide dismutase reveals another type of active site.,Wuerges J, Lee JW, Yim YI, Yim HS, Kang SO, Djinovic Carugo K Proc Natl Acad Sci U S A. 2004 Jun 8;101(23):8569-74. Epub 2004 Jun 1. PMID:15173586
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↑ Wuerges J, Lee JW, Yim YI, Yim HS, Kang SO, Djinovic Carugo K. Crystal structure of nickel-containing superoxide dismutase reveals another type of active site. Proc Natl Acad Sci U S A. 2004 Jun 8;101(23):8569-74. Epub 2004 Jun 1. PMID:15173586 doi:http://dx.doi.org/10.1073/pnas.0308514101