J. Foote et C. Milstein, CONFORMATIONAL ISOMERISM AND THE DIVERSITY OF ANTIBODIES, Proceedings of the National Academy of Sciences of the United Statesof America, 91(22), 1994, pp. 10370-10374
The fact that one cell encodes a single antibody sequence does not nec
essarily mean that the resulting antibody folds into a single structur
e, although this is a common assumption. Here we challenge this view a
nd suggest that many antibodies do not have a single conformation at t
he combining site. The basis for this proposal comes from the kinetic
analysis of a set of murine hybridomas derived from defined stages of
the immune response to 2-phenyl-5-oxazolone (Ox). Among them we have i
dentified three antibodies that exhibit complex hapten-binding kinetic
s. We observed biphasic or triphasic reactions in stopped-flow fluores
cence experiments, indicating that ligand binding involved isomerizati
on, as well as associative steps. The existence of an equilibrium betw
een at least two antibody conformations, with ligands binding preferen
tially to one form, was deduced from the variation with hapten concent
ration of the apparent rate of each phase.