|
Protein A isolated from Staphylococcus aureus, and Protein G obtained from Streptococcus bacteria, bind specifically to the Fc region on immunoglobulin molecules from a variety of different species. This Fc specific binding does not interfere with an antibody's ability to react with antigen, thus Protein A and Protein G are widely used in studies of cell surface antigens and receptors, cell development, immunoglubulin structure and function, and many other areas of immunology biochemistry and cell research. Protein A consists of four Fc-binding regions and each Protein A molecule is able to bind two or more immunoglobulin molecules. Protein G has been genetically modified to improve its utility in immunological applications. The region of native Protein G responsible for albumin binding has been removed, while retaining the region responsible for IgG binding.
Protein G binds strongly to many IgGs from species to which Protein A binds weakly, or not at all. These include IgGs from Goat, Sheep, Horse, Cow, Rat and Mouse. Both Protein A and Protein G bind strongly to Human, Rabbit and Guinea Pig IgG. Protein A also binds to Human IgA, IgM, and IgE, while Protein G does not.
Protein A and Protein G, when conjugated to enzymes or fluoroscopes can be used in place of a secondary antibody conjugate to detect antigen in various immunological applications such as ELISA tissue staining and immunoblotting These reagents are particularly useful in laboratories using primary antibodies from a number of species.
|
