Open AccessAn Engineered Arginine Residue of Unusual pH-Sensitive Reactivity Facilitates Site-Selective Antibody Conjugation
Author(s) -
Napon Nilchan,
James M Alburger,
William Roush,
Christoph Rader
Publication year - 2021
Publication title -
biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.43
H-Index - 253
eISSN - 1520-4995
pISSN - 0006-2960
DOI - 10.1021/acs.biochem.0c00955
Subject(s) - chemistry , conjugate , phenylglyoxal , residue (chemistry) , immunoconjugate , hapten , antibody , arginine , lysine , conjugated system , stereochemistry , combinatorial chemistry , biochemistry , monoclonal antibody , amino acid , biology , mathematical analysis , mathematics , organic chemistry , immunology , polymer
Monoclonal antibody h38C2 is a humanized catalytic antibody that has been used to generate various immunoconjugate species such as chemically programmed antibodies, antibody-drug conjugates, and antibody-siRNA conjugates. Highly efficient and specific conjugation of h38C2 occurs at its uniquely reactive lysine (Lys) residue buried inside the antibody's catalytic pocket. We recently reported the rational mutation of this Lys residue at position 99 in the heavy chain variable domain to an arginine (Arg) residue. The Lys99Arg mutation can be site-selectively conjugated with molecules containing a hapten-like triazolyl-phenylglyoxal (TPG) unit. Here we show that this conjugation is facilitated by the unusual pH-sensitive reactivity of the Arg99 residue, consistent with an indirectly measured p K a of 5.2. The Arg99/TPG conjugation holds promise to further expand the versatility of the h38C2 conjugation platform, such as for the generation of antibody conjugates with dual payloads.