Structure studies on human serum γ-globulins and myeloma proteins: III. Oxidative sulfitolysis of myeloma globulins and reconstitution of the macromolecules

Abstract

Individual specimens of myeloma globulins were cleaved by sulfite and cuprammonium ion, and the fragments were separated by gel filtration in acetic acid. Molecular weight determination indicated that both the H and L chains, after separation, recovery, and redissolution in a weakly alkaline solvent, appeared as dimers. When the cleaved globulins were treated with mercaptoethanol, the disulfide bonds were reformed. The reconstituted globulins appeared similar to the original native material in molecular weight and immunodiffusion tests. Slight differences were found in the optical rotatory dispersion behavior of the native and the reconstituted globulins. Individual specimens of the globulins differed among themselves and from normal γ-globulin with respect to the H L ratio, quantity of free N-terminal amino acids, and ease of reconstitution; but their chain conformations were similar. Significant differences were found in amino acid composition and peptide patterns between the H and L chains, and between individual L chains. The L chains showed similarity to Bence-Jones proteins in redissolving on boiling, conformation, immunodiffusion, and electrophoretic mobility in gels.