[Study of the oligonucleotide binding sites on an immunoglobulin molecule]

Interaction of IgG molecules with oligonucleotides using reactive derivatives of p(T)16 bearing a 4-[(N-2-chloroethyl-N-methyl)amino]benzylamine residue at the 5'-terminal phosphate was investigated. The modified immunoglobulins were degraded with pepsin into Fab and Fc fragments and by incomplete CNBr hydrolysis into smaller peptides. It became obvious from the analysis of the peptides obtained that the oligonucleotides contacted with immunoglobulins at the antigen-binding Fab fragment of the molecule. The site of interaction is localized in the light-chain N-terminal fragment 178 amino acids long. These facts are in accordance with our previous data about the ability of a specific antigen to prevent the oligonucleotide-antibody interaction. On the contrary, an oligonucleotide covalently linked with immunoglobulin could not prevent the antigen-antibody reaction. Monoclonal Fab fragments modified with the alkylating p(T)16 derivative were found to interact with the specific antigen (human myoglobin) during affinity chromatography. This interaction deserves further investigation because of its importance in studying the fate of oligonucleotides in vivo.