Application of 13C NMR spectroscopy to paratope mapping for larger antigen-Fab complexes

For the purpose of engineering the antibody combining site, mapping residues that are involved in antigen binding provide us with valuable information. By use of 13C NMR spectroscopy with selectively 13C-labeled Fv fragments, we have established a general strategy to identify the residues that are perturbed upon binding of small antigen (hapten) molecules [(1990) Biochemistry 30, 6604-6610]. In the present paper, we demonstrate that this strategy can be extended to molecular structural analyses of the complexes of an Fab fragment and a larger antigen molecule such as Pseudomonas aeruginosa exotoxin A with a molecular mass of 67 kDa.