What are the differences between Protein A, Protein G, Protein A/G, and Protein L Ig-binding proteins?
Protein A, Protein G, and Protein A/G bind almost exclusively to the IgG class of antibodies, but their binding properties differ among species and subclasses of IgG. Protein L binds in the variable fragment of some kappa light chains and can react with any immunoglobulin, not just IgG, as long as the correct kappa light chains are present. Protein L does not bind lambda light chains and certain kappa chains of different species.
-Protein A is generally preferred for rabbit, pig, dog, and cat IgG.
-Protein G has better binding capacity for a broader range of mouse and human IgG subclasses (e.g., IgG1 vs. IgG2)
-Protein A/G is a recombinant fusion protein that includes the IgG-binding domains of both Protein A and Protein
G. Therefore, Protein A/G is ideal for binding the broadest range of IgG subclasses from rabbit, mouse, human, and other mammalian samples.
-Protein L binds to certain immunoglobulin kappa light chains. Because kappa light chains occur in members of all classes of immunoglobulin (i.e., IgG, IgM, IgA, IgE and IgD), Protein L can purify these different classes of antibody. However, only those antibodies within each class that possess the appropriate kappa light chains will bind. Generally, empirical testing is required to determine if Protein L is effective for purifying a particular antibody. It binds only Vk1 in mouse and VkI, VkIII and VkIV in human.
Read more about the general characteristics of Ig-binding proteins (https://www.thermofisher.com/us/en/home/life-science/antibodies/antibody-purification-kits-reagents.html) and (https://assets.thermofisher.com/TFS-Assets/LSG/Application-Notes/TR0034-Ab-binding-proteins.pdf).
Find additional tips, troubleshooting help, and resources within our Protein Purification and Isolation Support Center.
