Enhancement of Solubility and Specific Activity of a Cu/Zn Superoxide Dismutase by Co-expression with a Copper Chaperone in Escherichia coli

BACKGROUND: Human Cu/Zn superoxide dismutase (hSOD1) is an antioxidant enzyme with potential as a therapeutic agent. However, heterologous expression of hSOD1 has remained an issue due to Cu(2+) insufficiency at protein active site, leading to low solubility and enzymatic activity. OBJECTIVES: The effect of co-expressed human copper chaperone (hCCS) to enhance the solubility and enzymatic activity of hSOD1 in E. coli was investigated in the presence and absence of Cu(2+). MATERIALS AND METHODS: pETDuet-1-hSOD1 and pETDuet-1-hCCS-hSOD1 were constructed and individually transformed into E. coli strain BL21(DE3). The recombinant hSOD1 was expressed and purified using immobilized metal affinity chromatography. The yield and specific activity of hSOD1 in all conditions were studied. RESULTS: Co-expression with hCCS increased hSOD1 solubility at 37°C, but this effect was not observed at 25°C. Notably, the specific activity of hSOD1 was enhanced by 1.5 fold and greater than 3 fold when co-expressed with hCCS at 25°C with and without Cu(2+) supplement, respectively. However, the chaperone co-expression did not significantly increase the yield of hSOD1 comparable to the expression of hSOD1 alone. CONCLUSIONS: This study is the first report demonstrating a potential use of hCCS for heterologous production of hSOD1 with high enzymatic activity.