Over-expression of the chaperonins GroEL and GroES significantly suppressed the temperature-dependent pattern of expression of Cu,Zn superoxide dismutases in Escherichia coli and increased the yield of active enzyme. The results obtained indicate that chaperonins prevent degradation of metal-deficient enzyme molecules. GroEL was shown to form a complex with unfolded Cu,Zn superoxide dismutase in vitro, confirming that GroEL can interact with beta-stranded proteins.