Fig. 2.

Hapten or protein binding selects pre-existing conformations of the antibody SPE7. Two distinct conformations of unbound SPE7 (AB1: 1OAQ; AB2: 1OCW) have been characterized in which part of the binding site consisting of Y34, W93 and N96 of the light chain are in different conformations. Owing to the orientation of W96, the binding site of the major conformation, AB1, is considerably ‘flatter’ than AB2. Ligand binding selects from these pre-existing substates, with protein-binding (AB4: 1OAZ) maintaining the AB1-like conformation of these residues and hapten-binding (DNP-Serine; AB3: 1OAU) maintaining an AB2-like conformation