INTERACTIONS BETWEEN STAPHYLOCOCCAL PROTEIN-A AND IMMUNOGLOBULIN DOMAINS

The affinity and stoichiometry of interaction between staphylococcal protein A and different domains of immunoglobulins have been studied. Light scattering and tryptophan fluorescence quenching titrations along with direct binding assays were performed. The lack of binding to protein A of pFc′ fragment (corresponding to CH3 domain of IgG) or of Facb derivative of rabbit IgG (which is devoid of the CH3) suggests that the locus of protein A binding is at the interface between the CH2 and CH3 domains. This assignment is also supported by results of the tryptophan fluorescence quenching and C1 binding experiments. © 1978.