Antibody combining site crystallography

David R. Bundle (Canada) Oligosaccharide-protein interactions. Studies of antibody-combining sites by competitive bonding, sequence analysis and X-ray crystallography... 

In addition to X-ray crystallography, two approaches have been used to locate the antibody combining site in immunoglobulins and to deduce the structural basis of antibody specificity. One method is based on the known dependence of protein conformation on amino acid sequence, i.e., the specificity of antibodies must be a reflection of positions having specific amino acid residues. Hence, comparison of a set of homogeneous myeloma proteins would be expected to define regions of variable primary... 

Figure 4. (a) Selected residues from the combining site of antibody 5C8 com-plexed to piperidine-A/-oxide hapten 4, as determined by X-ray crystallography.1151 The linker portion of the hapten has been truncated to a methyl for comparison with the theozyme complex, (b) The formate/formic acid theozyme complexed to the model of hapten 4, as optimized through quantum mechanical calculations.161... 

Competitive Inhibition Enzyme Assays. Estimates of antibody-lysozyme dissociation constants can be obtained by taking advantage of the fact that most monoclonal antibodies efficiently inhibit enzymatic activity.3 5 The combining site of HyHEL-10, which is presented as an example, also has been demonstrated by X-ray crystallography to overlap a portion of the catalytic site of lysozyme.7 A constant concentration of lysozyme is incubated with varying amounts of antibody, and amounts of free (unbound) lysozyme molecules are estimated by the proportion of catalytic activity remaining. The assay assumes that the addition of Micrococcus lysodeikticus cell walls and concurrent dilution of the antibody-antigen mixture do not disturb the equilibrium. 

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