Role of Antigenic Conformation in the Antigen–Antibody Complex Formation

Abstract

THE immunochemical reactivity of a protein molecule may be affected by its conformation in two ways: (1) a particular conformation may expose or mask primary antigenic sites on the polypeptide chain; (2) the con-formational flexibility (allosteric properties) of a protein may determine the steric fit between antigen (Ag) and antibody (Ab) molecules^1–5. The effect of conformation may be particularly significant in the soluble Ag–Ab lattice formation, for the availability of antigenic sites and the steric fit between Ag and Ab would determine the size and stoichiometric composition of the lattice. A conformationally flexible protein would be expected to form Ag–Ab lattices more readily than a rigid protein, and this would be expressed either by an increased rate in lattice formation, an increased size of the Ag–Ab lattice, an increased amount of Ab in the lattice or an increased stability of the formed lattice.