Evidence for a single-chain structure of native human ceruloplasmin using sodium dodecyl sulfate-polyacrylamide-crossed immunoelectrophoresis

A simple method is described for the analysis of proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis combined with crossed immunoelectrophoresis. The technique allows the identification of specific proteins and estimation of their molecular weights after the electrophoresis of complex mixtures such as blood plasma. Human ceruloplasmin was estimated to have a molecular weight of 128,000 using this method. Reduction of plasma with 2-mercaptoethanol in the presence of protease inhibitors did not result in dissociation of ceruloplasmin into detectable smaller subunits, suggesting that native ceruloplasmin is composed of a single polypeptide chain.