Immunoglobulin G-binding protein G, Streptococcus sp. group G (IgG-binding protein G)

Protein G is a cell wall protein derived from group G of Streptococcus. The immunoglobulin binding region of protein G mainly interacts with the Fc fragment of IgG. This region contains three single domains consisting of 55 amino acids, C1, C2, and C3, which are separated by the interval regions D1 and D2 composed of 16 amino acids respectively. Each single domain is able to bind to Fc fragments of antibody IgG. Protein G can bind specifically to the Fc region of IgG. Protein G has A higher affinity for most mammalian IgG than Protein A, with lower serum protein binding levels, higher purity, and relatively lower ligand shedding. Especially for the subunits of IgG, such as human IgG3, mouse IgG1, and mouse IgG2a. Therefore, Protein G can be used to purify mammalian monoclonal and polyclonal antibodies that do not bind well to Protein A.