2C9U:
reference: Variable metallation of human superoxide dismutase: atomic resolution crystal structures of Cu-Zn, Zn-Zn and as-isolated wild-type enzymes., Strange RW, Antonyuk SV, Hough MA, Doucette PA, Valentine JS, Hasnain SS, J Mol Biol. 2006 Mar 10;356(5):1152-62. Epub 2005 Dec 12. PMID: 16406071

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