Subunit structure of human superoxide dismutase.

A subunit structure for human superoxide dismutase has been demonstrated by sedimentation equilibrium, agarose gel filtration, and sodium dodecyl sulfate polyacrylamide gel electrophoretic studies. This protein appears to be composed of 2 subunits, not linked by covalent bonds, each with a molecular weight about 16,000. Dissociation of the subunits is facilitated by alkylation of the two sulfhydryl groups in the protein, by removal of the copper and zinc, by reduction and alkylation of the protein, or by succinylation. The two free sulfhydryl groups were labeled with [14C]iodoacetate and isolated in two nonidentical peptides.