Protein L, first isolated from the surface of bacterial species Peptostreptoccus magnus, binds immunoglobulin through κ light chain interaction. Protein L binds a wider range of Ig classes and subclasses than other antibody-binding proteins such as protein A or protein G. It can bind to all classes of Ig (i.e., IgG, IgM, IgA, IgE, and IgD) and also the single chain variable fragments (Scfv) and Fab fragments.