Mapping Epitope Structure and Activity: From One-Dimensional Prediction to Four-Dimensional Description of Antigenic Specificity

Our knowledge of antigenic specificity has greatly increased in recent years mainly through X-ray crystallographic studies of proteins and peptides complexed with monoclonal antibodies. However, our ability to predict the location of antigenic sites in proteins remains limited partly because prediction algorithms reduce the complexity of epitopes to one-dimensional, linear peptide models. Epitopes and paratopes are relational entities definable by their mutual complementarity and adaptation potential as well as by their activity. A complete account of antigenic specificity demands the integration of both structural and binding activity data that can be achieved only through a spatiotemporal four-dimensional analysis. Failure to include the fourth dimension, i.e., time, in the analysis of antigen-antibody complementarity amounts to considering proteins as rigid bodies and ignores the mutual adaptation that occurs when the two partners interact. Reducing four-dimensional protein systems to three-dimensional or two-dimensional representations inevitably distorts our perception of the dynamic nature of epitopes.