Recombinant Streptococcal Protein G (r-SPG)

Protein G is a bacterial cell wall protein expressed on the cell surface of certain strains of group C and G streptococci that binds to the Fc region of immunoglobulin G (IgG) with high affinity. Protein G binds to all IgG subclasses from human species, mice, and rats. It also binds to IgG from guinea pig, rabbit, goat, cow, sheep, and horse. Protein G exhibits a broader range of binding to IgG subclasses than does staphylococcal protein A.

Some of the most important areas of application for G protein are the isolation and purification or removal of IgG from serum, the purification of monoclonal antibodies, and the isolation of immune complexes. Protein G conjugates are commonly used as affinity adsorbents to purify immunoglobulins (antibodies) and immunoglobulin subtypes from serum, hybridoma ascites, tissue culture supernatants, and other biological fluids.

In addition to the Fc receptor, intact G protein has membrane-spanning regions as well as specific binding sites for albumin and the Fab region of immunoglobins. Albumin and cell surface binding domains were removed from the recombinant G protein to ensure maximum specific IgG binding capacity.

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