Multivalent Binding and Functional Affinity

Abstract

The evolutionary development of the architecture of the antibody molecule has provided in its contemporary form a distinctive structure superbly suited for multivalent interaction. In addition to multivalence, the general occurrence of multiple and identical antigenic determinants on the surfaces of infectious agents and neoplastic cells has led to the emergence of two further structural features. These, indeed, are required for the effective utilization of the multivalence of antibody. They comprise the property of intramolecular structural symmetry, i.e., identical subunits, resulting in the identity of the antigen-binding sites of the antibody, and the segmental flexibility of the Fab portions of the molecule. The conjunctive effect of these properties is the capacity of the antibody molecule to adjust the separation and relative orientation of its binding sites to the generally fixed distances between the identical complementary groups of the complex ligand. The biological utility of the resulting multivalent interaction is undoubtedly linked to the enhanced affinity which is associated with multivalent binding.