Formation of interchain disulfide bonds in Bence Jones proteins and immunoglobulins

Abstract

The formation of the interchain disulfide bonds in partially reduced Bence Jones proteins and immunoglobulins was studied in the presence of glutathione. It was found that only oxidized glutathione (GSSG) was effective for the formation of the interchain disulfide bonds in type gamma Bence Jones proteins and IgG. In type kappa Bence Jones proteins, on the other hand, no formation of the inter L-L disulfide bond was observed in the presence of GSSG at above pH 6. The kinetic pattern of disulfide bond formation of Bence Jones proteins was well interpreted by assuming that two monomers of a type gamma protein dimer are discriminated (monomers 1 and 2) and that only an intermediate in which the SH group on monomer 1 is blocked with GSSG can form a disulfide-bonded dimer and the intermediate in which the SH group on monomer 2 is blocked with GSSG can not. Comparison of the kinetic data for the formation of the interchain disulfide bonds of IgG with those for Bence Jones proteins suggested that H chain-GSSG mixed disulfide is a principal intermediate for the formation of the inter H-L disulfide bond.