Association and dissociation kinetics of bobwhite quail lysozyme with monoclonal antibody HyHEL-5

The anti-hen egg lysozyme monoclonal antibody HyHEL-5 and itscomplexes with various species-variant and mutant lysozymeshave been the subject of considerable experimental and theoreticalinvestigation. The affinity of HyHEL-5 for bobwhite quail lysozyme(BWQL) is over 1000-fold lower than its affinity for the originalantigen, hen egg lysozyme (HEL). This difference is believedto arise almost entirely from the replacement in BWQL of thestructural and energetic epitope residue Arg68 by lysine. Inthis study, the association and dissociation kinetics of BWQLwith HyHEL-5 were investigated under a variety of conditionsand compared with previous results for HEL. HyHEL-5–BWQLassociation follows a bimolecular mechanism and the dissociationof the antibody–antigen complex is a first-order process.Changes in ionic strength (from 27 to 500 mM) and pH (from 6.0to 10.0) produced about a 2-fold change in the association anddissociation rates. The effect of viscosity modifiers on theassociation reaction was also studied. The large differencein the HEL and BWQL affinities for HyHEL-5 is essentially dueto differences in the dissociation rate constant.