Copper-zinc superoxide dismutase crystal structure

I. The Need for Superoxide Dismutase II. The Crystal Structures of Dimeric Copper-Zinc Superoxide Dismutases... 

Superoxide dismutase catalyzes the disproportionation of superoxide as 2O2 -i- 2H — O2 -I- H2O2. The Cu,Zn-superoxide dismutases are widely distributed in both plant and animal kingdoms and are found in eukaryotic cytosols. The vast majority of studies on superoxide dismutases have been made on the enzyme from bovine erythrocytes this enzyme contains 151 amino acid residues and two copper and two zinc atoms per molecule of —32,000 Da. The crystal structure of this protein has been reported (97), and the active site was shown to consist of a bimetallic (Cu,Zn) assembly (see Fig. 6). A type-2 copper center is... 

It has been concluded from a study of the optical and e.p.r. spectra of Co —Cu bovine superoxide dismutase, in which zinc has been replaced by cobalt, that the cobalt site reactivity should be described in terms of reaction of the Co-imidazolate-Cu system as a whole the crystal structure reported last year indicated that the metals were linked by a common histidine residue. There is an exchange interaction between the cobalt and copper however, this is abolished when the linking imidazole is protonated. Further evidence for the close proximity and interactive dependence of the zinc and copper binding sites was obtained from a study of the 4 Cu protein a two-fold enhancement of the activity of 2 Cu dismutase was observed upon occupation of the zinc sites by the Cu ". On the basis of C1 n.m.r. studies, Fee and Ward have suggested that one co-ordination position of Cu in superoxide dismutase is normally occupied by water they further suggest that superoxide can displace the solvent to form a cupric peroxide complex. 

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