Protein L from Peptostreptococcus magnus binds to the kappa light chain variable domain

Research output: Contribution to journalArticle


Protein L is an immunoglobulin light chain-binding protein expressed by some strains of the anaerobic bacterial species Peptostreptococcus magnus. The major variable region subgroups of human kappa and lambda light chains were tested for protein L binding; V kappa I, V kappa III, and V kappa IV bound protein L, whereas no binding occurred with proteins of the V kappa II subgroup or with any lambda light chain subgroups. Studies of the protein L binding capacity of naturally occurring VL fragments, and VL- and CL-related trypsin- and pepsin-derived peptides prepared from a kappa I light chain, localized the site of interaction to the VL domain. The affinity constant for the binding to an isolated V kappa I fragment was comparable to that for the native protein (Ka 0.9 x 10(9) M-1 and Ka 1.5 x 10(9) M-1, respectively). No binding occurred with CL-related fragments. Extensive reduction and alkylation of the V kappa fragment or the native kappa chain resulted in complete loss of protein L binding. Although it is possible, from comparative amino acid sequence data, to identify certain VL-framework region residues that account for the selective binding of protein L by kappa I, kappa III, and kappa IV proteins, our studies indicate that this interaction is essentially dependent upon the tertiary structural integrity of the kappa chain VL domain.


External organisations
  • University of Tennessee
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Medicinal Chemistry


  • Amino Acid Sequence, Bacterial Proteins, Chromatography, Liquid, Electrophoresis, Polyacrylamide Gel, Humans, Immunoglobulin Variable Region, Immunoglobulin kappa-Chains, Molecular Sequence Data, Pepsin A, Peptostreptococcus, Protein Conformation, Radioimmunoassay, Trypsin, X-Ray Diffraction, Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.
Original languageEnglish
Pages (from-to)2234-9
JournalJournal of Biological Chemistry
Issue number4
Publication statusPublished - 1992 Feb 5
Publication categoryResearch