Nuclear magnetic resonance studies of antibody-antigen interactions

NMR is a useful method for studying antibody-antigen interactions in solution but the large size of the molecules makes interpretation of the data difficult. Multinuclear NMR and a family of switch variant antibodies and their proteolytic fragments are used to circumvent this problem and investigate the process of molecular recognition in antibody function. An Fv fragment has been prepared in high yield from a mouse IgG2a anti-dansyl-L-lysine monoclonal antibody in which the entire CH1 domain is deleted. 13C NMR resonances are observed for switch variant antibodies selectively labelled by 13C at the carbonyl carbon. Using a double-labelling method, site-specific assignments have been completed for all the methionine resonances in these antibodies. Comparison of the NMR spectra for intact antibodies and those of their proteolytic fragments suggests that carbonyl carbon chemical shift data can provide information on the way in which information is transmitted through different domains on antigen binding. Selective labelling of the antibody with 1H, 13C or 15N followed by nuclear Overhauser effect spectroscopy has identified some of the residues involved in antigen binding and indicated that the structure of the Fv fragment is significantly affected by antigen binding.