Superoxide dismutase copper binding

J.S. Valentine, M.W. Pantoliano, PJ. Mcdonnell, A.R. Burger, and S.J. Lippard, pH-dependent migration of copper(II) to the vacant zinc-binding site of zinc-free bovine erythrocyte superoxide dismutase. Proc. Natl. Acad. Sci. U.S.A. 76, 4245-4249 (1979). 

M.W. Pantoliano, P.J. McDonnell, and J.S. Valentine, Reversible loss of metal ions from the zinc binding site of copper-zinc superoxide dismutase. The low pH transition. J. Amer. Chem. Soc. 101, 6454— 6456 (1979). 

Wang, J., Xu, G., Gonzales, V. et al. Fibrillar inclusions and motor neuron degeneration in transgenic mice expressing superoxide dismutase 1 with a disrupted copper-binding site. Neurobiol. Dis 10 128-138,2002. 

Adults require 1-2 mg of copper per day, and eliminate excess copper in bile and feces. Most plasma copper is present in ceruloplasmin. In Wilson s disease, the diminished availability of ceruloplasmin interferes with the function of enzymes that rely on ceruloplasmin as a copper donor (e.g. cytochrome oxidase, tyrosinase and superoxide dismutase). In addition, loss of copper-binding capacity in the serum leads to copper deposition in liver, brain and other organs, resulting in tissue damage. The mechanisms of toxicity are not fully understood, but may involve the formation of hydroxyl radicals via the Fenton reaction, which, in turn initiates a cascade of cellular cytotoxic events, including mitochondrial dysfunction, lipid peroxidation, disruption of calcium ion homeostasis, and cell death. 

Curtain, C.C., Ali, F., Volitakis, I., Cherny, R.A., et al. (2001) Alzheimer s disease amyloid-beta binds copper and zinc to generate an allosterically ordered membrane-penetrating structure containing superoxide dismutase-like subunits, J. Biol. Chem., 276, 20466-20473. 

Fig. 6. Suggested changes in the coordination at tte copper (xntre upon anion binding and during the catalytic cycle of Cu—Za superoxide dismutase...

Peroxynitrite reacts with the active site of superoxide dismutase (SOD) to form a nitronium-like species (Fig. 37), analogous to the Fe EDTA reactions described earlier. However, copper in the active site of superoxide dismutase was necessary for the formation of the adduct. Removing copper from the active site by reduction with borohydride and dialysis against 50 mM KCN resulted in no adduct being formed, while restoration of copper to the active site gave back full enzyme activity. To account for the essential role of copper in the active site and the subsequent formation of 3-nitrotyrosine located 18-21 A distal from the active site, we proposed that peroxynitrite is attracted by the same electrostatic force field that draws superoxide into the active site (Beckman et al., 1992 Ischiropoulos et al., 1992b). Peroxynitrite appears to bind to copper in the active site to form a transient cuprous adduct as shown. 

The enzyme copper, zinc superoxide dismutase (Cu,Zn-SOD, EC 1.15.1.1) catalyzes the disproportionation of superoxide anion to dioxygen and hydrogen peroxide (equations 1 and 2). Crystallographic data can be found in References 41-46. This antioxidant enzyme is present in the cytosol and mitochondrial intermembrane space of eukaryotic cells and in the periplasmic space of bacterial cells as a homodimer of 32 kDa. Each monomer binds one copper and one zinc ion. The reaction mechanism involves the... 

Valentine, J. S., Pantoliano, M. W. Metal binding properties of copper-zinc superoxide dismutase. In Chemical and Biochemical Aspects of Superoxide and Superoxide Dismutase... 

Cass, A. E. G., Hill, H. A. O. Anion binding to copper(I) superoxide dismutase A high resolution H nuclear magnetic resonance spectroscopic study. In Chemical and Biochemical Aspects of Superoxide and Superoxide Dismutase (Bannister, J. V., Hill, H. A, O., eds.). New York-Amsterdam-Oxford, Elsevier/North-Holland, 1980, pp. 290-298... 

Sette, M., Paci, M., Desideri, A. and Rotillo, G. (1992) Formate as an NMR probe of anion binding to copper-zinc and copper-cobalt bovine erythrocyte superoxide dismutase. Biochemistry, 31, 2410-2415. 

Some metal- (especially copper) complexes catalyse the dismutation of superoxide at rates that compare favourably with catalysis by superoxide dismutase. One could therefore argue that the presence of such complexes in vivo might be beneficial. There are, however, additional considerations (1) such metal complexes may also reduce hydrogen peroxide, which could result in the formation of hydroxyl radicals, and (2) it is extremely likely that the metal will be displaced from its ligands (even when those ligands are present in excess), and becomes bound to a biomolecule, thereby becoming less active as a superoxide dismutase mimic. As an example, copper binds well to DNA and catalyses the formation of hydroxyl radicals in the presence of hydrogen peroxide and ascorbate [30],... 

The role of copper in other disease states is being investigated. For Alzheimer s disease studies, it has been found that the amyloid precursor protein interacts with copper to produce increased oxidant damage, and trace amounts of copper promote the precipitation of the amyloid p protein. In familial myotrophic lateral sclerosis about a quarter of the cases are caused by inherited dominant mutations in the Cu/Zn superoxide dismutase that probably result in abnormal Cu binding and the generation of reactive oxygen species. Copper has also been proposed to be involved in prion metabolism and fimction however, whether or not this imphcates copper in the prion diseases is unclear at this time. ... 

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