MODIFICATION OF ARGININE IN ACTIVE SITES OF ANTIBODIES

Use of a 2,3-butanedione reagent to modify arginyl residues in proteins, as first described by Yankeelov et al. (Yankeelov, J., Jr., Kochert, M., Page, J., and Westphal, A. (1966), Federation Proc. 25,590), has been applied to antibodies. Antibodies were acetylated to prevent any modification of lysine by the reagent. Modification of up to 70% of arginyl residues in antibodies against negatively charged haptens (p-azobenzoate, p-azobenzenearsonate, and succinamate) resulted in loss of active sites or in loss of specific binding activity. The presence of hapten during the modification reaction prevented such losses in whole or in part. Modification of arginine in antibodies against a positively charged hapten (p-azophenyltrimethylammonium) or a neutral hapten (3-azopyridine) resulted in no loss of sites or alteration of binding constants for these antibodies. The results implicate the presence of arginine in the active sites of antibodies against the negatively charged haptens and the absence of arginine in the sites of antibodies against the positively charged and neutral haptens. © 1968, American Chemical Society. All rights reserved.