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Comparison of Antibody IgG Binding Proteins

Protein A, Protein G, Protein A/G and Protein L are native and recombinant proteins of microbial origin that bind to mammalian immunoglobulin molecules. These proteins are available in purified, salt-free, lyophilized form, as well as coated in microplates and covalently immobilized to various solid supports. The most popular support for affinity applications involving immunoglobulin proteins is crosslinked beaded agarose, although UltraLink Biosupport (polyacrylamide) and MagnaBind Magnetic Beads are also available. See product links at the bottom of this page.

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General Characteristics of Ig Binding Proteins.
  Native Protein A Recombinant Protein A Recombinant Protein G Recombinant Protein A/G Recombinant Protein L
Native Source Staphylococcus
Streptococcus N/A Peptostrepto-
coccus magnus
Production Source S. aureus E. coli E. coli E. coli E. coli
Molecular Weight 46,700 44,600 21,600 50,460 35,800
Apparent Mass by SDS-PAGE 42kDa 45kDa 32kDa 40 to 45kDa 36kDa
# Binding Sites for Ig 5 5 2 4+2 4
Albumin Binding Site No No No No No
Optimal Binding pH 8.2 8.2 5 5 to 8.2 7.5
Ig Binding Target Fc Fc Fc Fc VL-kappa

The four proteins bind almost exclusively with the IgG class of antibodies, but their binding properties differ among species and subclasses of IgG. 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 (IgG1, IgG2, etc.).

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.

Learn more...

View Tech Tip #34 for a more detailed summary of Protein A, G, A/G and L binding characteristics by antibody species and class, based on a review of original literature.

View products...

Product Type: Protein A Protein G Protein A/G Protein L
Purified Protein Protein A Protein G Protein A/G Protein L
Antibody Purification Kits Protein A Kits Protein G Kits Protein A/G Kits Protein L Kits
Agarose and Other Resins Protein A Resins Protein G Resins Protein A/G Resins Protein L Resins
Magnetic Beads Protein A Beads Protein G Beads Protein A/G Beads Protein L Beads
Coated Microplates Protein A Plates Protein G Plates Protein A/G Plates Protein L Plates
Written and/or reviewed by Douglas Hayworth, Ph.D.

Instructions | MSDS | CofA
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