Protein L is an immunoglobulin-binding protein that originates from the bacteria Peptostreptococcus magnus. Unlike Protein A and Protein G, which bind primarily through Fc regions (i.e., heavy chain) of immunoglobilins, Protein L binds Igs through interactions with the light chains. Because no part of the heavy chain is involved in the binding interaction, Protein L binds a wider range of Ig classes than Protein A or G. Protein L binds to representatives of all classes of Ig, including IgG, IgM, IgA, IgE and IgD. Single chain variable fragments (ScFv) and Fab fragments also bind to Protein L.

Despite this wide-ranging binding capability with respect to Ig classes, Protein L is not a universal immunoglobilin-binding protein. Binding of Protein L to immunoglobulins is restricted to those containing kappa light chains (i.e., k chain of the VL domain) [1]. In humans and mice, kappa (k) light chains predominate. The remaining immunoglobulins have lambda (l) light chains. Furthermore, Protein L is effective in binding only certain subtypes of kappa light chains. For example, it binds human VkI, VkIII and VkIV subtypes but does not bind the VkII subtype. Binding of mouse immunoglobulins is restricted to those having VkI light chains [1].

Given these specific requirements for effective binding, the main application for immobilized Protein L is purification of monoclonal antibodies from ascites or culture supernatant that are known to have the kappa light chain. Protein L is extremely useful for purification of VLk-containing monoclonal antibodies from culture supernatant because it does not bind bovine immunoglobilins, which are present in the media serum supplement. Also, Protein L does not interfere with the antigen-binding site of the antibody, making it useful for immunoprecipitation assays, even using IgM.

Protein L Agarose Highlights:

• Unique immunoglobulin binding specificity:†
  • Binds to kappa light chains on antibodies from a wide range of species without interfering with antigen-binding sites†
  • Binds to all classes of Ig (e.g., IgG, IgM, IgA, IgE and IgD)†
  • Binds single-chain variable fragments (ScFv)†
  • Does not bind bovine, goat or sheep Igs
  • Does not bind to bovine antibodies, making it ideal for purification of mouse IgG† from cell culture supplemented with bovine serum
  • † Note: Lambda light chains and some kappa light chains will not bind. Binding will only occur if the appropriate kappa light chains are present.
• Efficient and leach-resistant immobilization chemistries provide for high capacity and purity for antibody purification
• Available in regular and high ("Plus") binding-capacity formats
• Offered as resin slurries, chromatography cartridges, NAb Spin Columns and Purification Kits
  (Learn more about Pierce Chromatography Cartridges or about NAb Spin Columns.)

Applications for Protein L Agarose Resin:

• Purify monoclonal and polyclonal antibodies that bind poorly to Protein A or Protein G agarose
• Purify monoclonal antibodies from culture supernatants supplemented with bovine serum
• Protein L immunoprecipitation and co-immunoprecipitation assays
• Purify ScFv and Fab fragments containing kappa light chains

Choose between Protein A, Protein G, Protein L:

• Compare Protein A, Protein G and other antibody binding proteins
• Protein A, Protein G, Protein L affinity by species and antibody type

Related Products:

• Protein A Beads  •  Protein G Beads  •  Protein A/G Beads  •  Magnetic Beads
• Melon Gel IgG Purification Kits  •  IgG Binding and Elution Buffers
• Immunoprecipitation Kits  •  Co-Immunoprecipitation Kits

References:

1. Nilson, B.H., et. al.(1993). J. Immunol. Methods164, 33-40.
2. Bjorck, L., et. al.(1998). J. Immunol140, 1194-1197.
3. Kastern, W., et. al.(1992). J. Biol. Chem.267, 12820-12825.
4. Akerstrom, B., and Bjorck, L. (1989). J. Biol. Chem.264, 19740-19746.