Protein G, a bacterial cell wall protein isolated from group G Streptococci, binds to mammalian IgGs mainly through Fc regions. Native protein G has 3 IgG binding domains and also sites for albumin and cell-surface. Although protein G has very similar tertiary structures to protein A, their amino acid compositions differ significantly, resulting in different binding characteristics. Protein G can be used for purification of mammalian monoclonal and polyclonal IgGs that do not bind well to protein A.
PurKine™ Protein G Resin consists of 90μm beads of cross-linked 4% agarose, to which Recombinant protein G has been coupled. Recombinant Protein G, in which albumin and cell surface binding sites have been eliminated to reduce nonspecific binding, is produce in E. coli. This affinity resin is of high yield and high purity purification of whole IgG from mammalian serum and other fluids. Tests confirm that performance equals or exceeds popular recombinant protein G resins from other suppliers, and no decrease in performance occurs after at least five repeated uses.
PurKine™ Protein G Purification system has greater affinity than protein A for most mammalian IgGs, especially for certain subclasses including human IgG3,mouse IgG1 and rat IgG2a. Unlike protein A, protein G does not bind to human IgM, IgD and IgA. Per mL of the resin can capture more than 30mg human lgG. The resin is also available as prepacked column (PurKine™ Protein G Packed Column) and kit (PurKine™ Antibody Purification Protein G Kit) formats.