COVALENT STRUCTURE OF A HUMAN YGAMMA-IMMUNOGLOBULIN .2. ISOLATION AND CHARACTERIZATION OF CYANOGEN BROMIDE FRAGMENTS

A human γG-immunoglobulin (Eu) has been cleaved into ten different fragments by treatment with cyanogen bromide. These fragments have also been obtained by CNBr treatment of the light and heavy chains. The Fab(t) and Fc(t) fragments, produced by limited tryptic proteolysis of Eu, also yielded the expected CNBr fragments with one exception. The region of the heavy chain corresponding to CNBr fragment H4 was found to be cleaved by trypsin into two fragments, H4A (found in Fab(t)) and H4B (found in Fc(t)). The CNBr fragments were characterized in terms of molecular weight, amino acid composition, and terminal amino acid residues, and it was found that they accounted for the entire γG-immunoglobulin molecule. A partial arrangement of the cyanogen bromide fragments was made on the basis of their terminal amino acids and their location in the chains and tryptic fragments. © 1968, American Chemical Society. All rights reserved.