PROPERTIES OF THE PEPTIDE CHAINS OF NORMAL AND PATHOLOGICAL HUMAN γ GLOBULINS

Abstract

Normal and pathological human gamma-globulins have a basically similar structure and can be split by reduction and separated by gel-filtration into large A and smaller B chains; these chains are present in the same proportions in 7s gamma-, gamma1 A-and gamma1 M-globulins. Porter''s (1962) proposed four-chain structure for gamma-globulin is supported, with human gamma-globulin, by the relative yields of A and B chains, and their amino acid composition, sulphydryl content and stability after full reduction. An analysis of electrophoretic and antigenic properties indicates that the three main types of gamma-globulin have A chains that are structurally different. The papain fragment F consists of A chain. The B chains from normal 7s gamma- and gamma1 M-globulins are identical on electrophoresis. The B chain of 7s gamma-globulin carries the group-specific antigenic determinants (I and II) common to all gamma-globulins. These findings indicate that all types of gamma-globulin contain B chains of similar structure. The B chain is present in the papain fragment S. The B chains of myeloma proteins are less complex than those of normal proteins in electrophoretic and antigenic properties.