Subunit interactions in mouse myeloma proteins with anti-galactan activity

The interactions among the subunits of a unique set of mouse myeloma proteins having specificity for beta-D-(1,6) galactans has been studied by making homologous and heterologous recombinants of heavy and light chains. The recombinations were carried out by mixing together the desired heavy and light chains that had been separated on a Sephadex G-100 column in urea-acetic acid and renaturing the chains at near neutral pH. One homologous and six heterologous recombinants have been prepared. All the recombinants prepared possessed a four-chain native-like structure. The ligand binding activity and idiotypic specificity of the homologous recombinant were essentially indistinguishable from those of the original native protein. All the heterologous heavy-light chain combinations also led to the regeneration of functional binding sites. The affinity of the heterologous recombinants towards various galactose ligands was comparable to those of the native molecules. Furthermore, the ligand binding affinity of the recombinants was almost invariably closer to the Ka of the original protein that had a higher affinity. Idiotypic specificity of the heterologous recombinants paralleled that of the original protein that had contributed the heavy chain.