Staphylococcal protein A consists of five IgG-binding domains.
A genetic approach is described to clarify the IgG-binding properties of the N-terminal portion of staphylococcal protein A (region E). Several gene fragments, encoding region E or B or protein A, have been cloned and expressed in Escherichia coli. The gene products were purified by IgG-affinity chromatography and subjected to structural and functional analyses. Both fragments can be efficiently purified using this method, suggesting that region B as well as region E has Fc-binding activity. In addition, gene fusions were assembled giving fragments EB and EE, which both showed a divalent Fc-binding. These results demonstrate that protein A consists of five IgG-binding domains. The implications of these findings for the structure of protein-A--immunoglobulin-G complexes are discussed.
D000596:Amino Acids / Q000032:analysis; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005798:Genes, Bacterial; D010446:Peptide Fragments / Q000235:genetics; D010957:Plasmids; D014176:Protein Biosynthesis; D021382:Protein Sorting Signals / Q000032:analysis; D017452:Receptors, IgG; D011971:Receptors, Immunologic / Q000235:genetics*; D013205:Staphylococcal Protein A / Q000235:genetics*; D013210:Staphylococcus / Q000235:genetics; D014169:Transformation, Bacterial
D000596:Amino Acids; D010446:Peptide Fragments; D021382:Protein Sorting Signals; D017452:Receptors, IgG; D011971:Receptors, Immunologic; D013205:Staphylococcal Protein A