Antibody Multispecificity Mediated by Conformational Diversity

A single antibody was shown to adopt different binding-site conformations and thereby bind unrelated antigens. Analysis by both x-ray crystallography and pre-steady-state kinetics revealed an equilibrium between different preexisting isomers, one of which possessed a promiscuous, low-affinity binding site for aromatic ligands, including the immunizing hapten. A subsequent induced-fit isomerization led to high-affinity complexes with a deep and narrow binding site. A protein antigen identified by repertoire selection made use of an unrelated antibody isomer with a wide, shallow binding site. Conformational diversity, whereby one sequence adopts multiple structures and multiple functions, can increase the…