Role of the constant region domain in the structural diversity of human antibody light chains

Issues regarding the structural diversity (heterogeneity) of an antibody molecule have been the subject of discussion along with the development of antibody drugs. Research on heterogeneity has been extensive in recent years, but no clear solution has been reached. Heterogeneity is also observed in catalytic antibody k light chains (CLs). In this study, we investigated how the constant region domain of CLs concerns structural diversity because it is a simple and good example for elucidating heterogeneity. By means of cation‐exchange chromatography, SDS‐PAGE, and 2‐dimensional electrophoresis for the CL, multimolecular forms consisting of different electrical charges and molecular sizes coexisted in the solution, resulting in the similar heterogeneity of the full length of CLs. The addition of copper ion could cause the multimolecular forms to change to monomolecular forms. Copper ion contributed greatly to the enrichment of the dimer form of CL and the homogenization of the differently charged CLs. Two molecules of the CL protein bound one copper ion. The binding affinity of the ion was 48.0 μM21. Several divalent metal ions were examined, but only zinc showed a similar effect. —Hifumi, E., Taguchi, H., Kato, R., Uda, T. Role of the constant region domain in the structural diversity of human antibody light chains. FASEB J. 31, 1668–1677 (2017) www.fasebj.org