Expression of New Recombinant IgG-Binding Polypeptides and Analysis of Their Capacity to Bind Human IgG.

Protein G is present in group G streptococcus strain (G4223); the IgG-binding part of this protein contains three IgG-binding domains and binds human IgG with very high activity. We obtained two recombinant polypeptides G4223 and G4223 with high IgG-binding activity. Polypeptide G4223 consisting of three IgG-binding domains and W region has higher molecular weight and is characterized by higher affinity for IgG than polypeptide G4223 consisting of only three IgG-binding domains. It was shown that polypeptide affinity depends on its structure and size.