Structure of the M{alpha}2-3 toxin {alpha} antibody-antigen complex: combination of modelling with functional mapping experimental results

Modelled structures of the acetylcholine receptor-mimickingantibody, M2-3, both free and bound to its antigen, toxin ,are assessed in the light of new experimental mutational datafrom functional mapping of the paratopic region of M2-3. Theexperimental results are consistent with the previously-predictedstructure of the free antibody, and also demonstrate that structuralparticularities of the M2-3 combining site that were identifiedin the models play a role in the protein association. The modelledconformations of the hypervariable loops are discussed in thecontext of recent new data and analyses. The new mutationaldata allow several previously-considered modelled structuresof the complex to be rejected. Two quite similar models nowremain.