Protein A and G

Protein A and protein G are bacterial immunoglobulin (IgG) binding proteins. While protein A originates from Staphylococcus aureus, protein G is of Streptococcal origin. Rockland offers protein A and protein G in unconjugated and conjugated forms for common immunoassays, including ELISA, Western blotting, and immunohistochemistry.

Sepharose protein A, protein G, and protein A/G are widely used for immunoprecipitation and IgG purification. While both protein A and protein G bind to immunoglobulins from various species, their affinity differs in dependence on immunoglobulin classes as well as species origins.

Protein A and Conjugates

Protein A (Uniprot P38507) is a 56 kDa cell wall protein originated from Staphylococcus aureus. It contains five homologous Ig-binding domains. Each domain can bind the Fc fragment of a wide range of mammalian immunoglobulins. Protein A’s affinity to Fc may vary in dependence of IgG species origins or subclasses. Protein A is often coupled to solid matrices such as Sepharose™, magnetic particles, or latex for IgG purification from ascites, serum, or hybridoma culture media.

Protein G and Conjugates

Protein G (Uniprot P19909) is an immunoglobulin-binding protein from Streptococcal bacteria. As the native molecule also binds albumin, the albumin binding site has been removed from recombinant forms of Protein G. Much like Protein A, but with different IgG-binding specificities, Protein G is often used for immunoglobulin purification and detection.

Protein A and Protein G Sepharose™

Rockland’s Protein A, Protein G, and Protein A/G Sepharose™ are fast flow, low leakage, affinity resins designed for high purity separation of monoclonal and polyclonal antibodies at the laboratory and process scales. For each lot, IgG-binding capacity is validated by human IgG binding assays to ensure high quality. All Rockland Protein A and Protein G reagents undergo rigorous quality control to assure high-performance quality.