Biochemical Society Transactions

The Behaviour of Enzymes in Cells

Immunoglobulin-binding domains: Protein L from Peptostreptococcus magnus

N.G. Housden, S. Harrison, S.E. Roberts, J.A. Beckingham, M. Graille, E. Stura, M.G. Gore


Protein L is a multidomain cell-wall protein isolated from Peptostreptococcus magnus. It belongs to a group of proteins that contain repeated domains that are able to bind to Igs without stimulating an immune response, the most characterized of this group being Protein A (Staphylococcus aureus) and Protein G (Streptococcus). Both of these proteins bind predominantly to the interface of CH2-CH3 heavy chains, while Protein L binds exclusively to the VL domain of the κ-chain. The function of these proteins in vivo is not clear but it is thought that they enable the bacteria to evade the host's immune system. Two binding sites for κ-chain on a single Ig-binding domain from Protein L have recently been reported and we give evidence that one site has a 25–55-fold higher affinity for κ-chain than the second site.

  • dissociation constant
  • immunoglobulin
  • mutant
  • sequence


  • The Behaviour of Enzymes in Cells, a Biochemical Society-supported meeting held at Trinity College Dublin, 14 September 2002