ALL INDIVIDUAL DOMAINS OF STAPHYLOCOCCAL PROTEIN-A SHOW FAB BINDING

The interactions between the individual domains (E, D, A, B and C) of staphylococcal protein A (SPA) and Fc and Fab regions of human immunog lobulins were studied using real-time biospecific interaction analysis . An engineered domain Z, similar to fragment B but with a single glyc ine to alanine amino acid substitution, was also included in the study . The domains were expressed in Escherichia coli, affinity purified an d immobilised onto sensor chip surfaces in a directed manner using a u nique C-terminal cysteine residue engineered into the recombinant prot eins. All domains bound to a recombinant human IgG1 Fc fragment with s imilar strength. For the first time, binding to human Fab was demonstr ated for all native SPA domains, using both polyclonal F(ab')2 and a r ecombinant scFv fragment as reagents. Interestingly, the engineered Z domain showed a considerably lower affinity for Fab as compared to the native domains. (C) 1998 Federation of European Microbiological Socie ties. Published by Elsevier Science B.V.