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Acta Biochimica et Biophysica Sinica
Year: 2010  |  Volume: 42  |  Issue: 3  |  Page No.: 183 - 194

Roles of zinc and copper in modulating the oxidative refolding of bovine copper, zinc superoxide dismutase

H. T Li, M Jiao, J Chen and Y. Liang    

Abstract:

The structural integrity of the ubiquitous enzyme copper, zinc superoxide dismutase (SOD1) depends critically on the correct coordination of zinc and copper. We investigate here the roles of the stoichiometric zinc and copper ions in modulating the oxidative refolding of reduced, denatured bovine erythrocyte SOD1 at physiological pH and room temperature. Fluorescence experiment results showed that the oxidative refolding of the demetalated SOD1 (apo-SOD1) is biphasic, and the addition of stoichiometric Zn2+ into the refolding buffer remarkably accelerates both the fast phase and the slow phase of the oxidative refolding, compared with without Zn2+. Aggregation of apo-SOD1 in the presence of stoichiometric Zn2+ is remarkably slower than that in the absence of Zn2+. In contrast, the effects of stoichiometric Cu2+ on both the rates of the oxidative refolding and the aggregation of apo-SOD1 are not remarkable. Experiments of resistance to proteinase K showed that apo-SOD1 forms a conformation with low-level proteinase K resistance during refolding and stoichiometric Cu2+ has no obvious effect on the resistance to proteinase K. In contrast, when the refolding buffer contains stoichiometric zinc, SOD1 forms a compact conformation with high-level proteinase K resistance during refolding. Our data here demonstrated that stoichiometric zinc plays an important role in the oxidative refolding of low micromolar bovine SOD1 by accelerating the oxidative refolding, suppressing the aggregation during refolding, and helping the protein to form a compact conformation with high protease resistance activity.

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