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Description
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Protein L is a 36 kDa immunoglobulin-binding protein isolated from the bacteriaPeptostreptococcus magnus. Unlike Protein A and Protein G, which bind to the Fcregion of immunoglobulins (antibodies), Protein L binds antibodies through lightchain interactions. Protein L binds a wider range of antibody classes than ProteinA or G. Protein L binds to representatives of all antibody classes, including IgG,IgM, IgA, IgE and IgD. Single chain variable fragments (ScFv) and Fab fragmentsalso bind to Protein L. Protein L binding is restricted to those antibodies thatcontain kappa light chains and it is only effective in binding certain subtypes ofkappa light chains. Given these specific requirements for effective binding, themain application for immobilized Protein L is purification of monoclonal antibodiesfrom ascites or cell culture supernatant that are known to have the kappa lightchain. Protein L is extremely useful for purification of VLkappa-containingmonoclonal antibodies from culture supernatant because it does not bind bovineimmunoglobulins, which are often present in the media as a 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.
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