Succinylation of Gamma Globulin

Abstract

THE chemical modification of proteins with succinic anhydride was shown by Habeeb et al.¹ to result in an unfolding of the compact conformations of several proteins in neutral aqueous buffer. This was attributed to the large increase in net negative charge produced by the replacement of the positively charged ε-NH₃⁺ groups of lysine residues by negatively charged-NHCOCH₂CH₂COO-groups. An intensive study of the specificity of this reaction and of its conformational effects was made by Cherry² with the protein bovine serum albumin; the results have been briefly reported³. Utilizing these findings, Klotz and Keresztes-Nagy⁴ made the interesting observation that the electrostatic repulsions introduced by succinylation could result in the complete dissociation of non-covalently linked sub-units of proteins, in particular, those of haemerythrin, at neutral pH without the addition of any other dissociating agents such as urea or detergent. We have now shown that rabbit γ-globulin, succinylated either before or after partial reduction of interchain disulphide bonds⁵, can be separated into its constituent heavy and light peptide chains^5,6 by gel-filtration in aqueous buffers at pH near neutrality without the use of detergents⁷. Furthermore, the isolated succinylated heavy and light chains are quite soluble in such buffers, whereas isolated but unmodified heavy chains are insoluble⁶.