Analysis of plasminogen-binding M proteins of Streptococcus pyogenes

Methods. 2000 Jun;21(2):143-50. doi: 10.1006/meth.2000.0985.


Group A streptococci are common human pathogens that cause a variety of infections. They express M proteins which are important cell wall-bound type-specific virulence factors. We have found that a set of strains, associated primarily with skin infections, express M proteins that bind plasminogen and plasmin with high affinity. The binding is mediated by a 13-amino-acid internal repeated sequence located in the N-terminal surface-exposed portion of these M proteins. This sequence binds to kringle 2 in plasminogen, a domain that is not involved in the interaction with streptokinase, a potent group A streptococcal activator of plasminogen. It could be demonstrated that plasminogen, absorbed from plasma by growing group A streptococci expressing the plasminogen-binding M proteins, could be activated by exogenous and endogenous streptokinase, thereby providing the bacteria with a surface-associated enzyme that could act on the tissue barriers in the infected host.

MeSH terms

  • Antigens, Bacterial*
  • Bacterial Outer Membrane Proteins*
  • Bacterial Proteins / analysis
  • Bacterial Proteins / metabolism*
  • Binding Sites
  • Blotting, Western
  • Carrier Proteins / analysis
  • Carrier Proteins / metabolism*
  • Cloning, Molecular
  • Electrophoresis, Agar Gel / methods
  • Electrophoresis, Polyacrylamide Gel / methods
  • Humans
  • Plasminogen / metabolism*
  • Protein Binding
  • Recombinant Fusion Proteins / analysis
  • Recombinant Fusion Proteins / metabolism
  • Streptococcus pyogenes / pathogenicity*
  • Streptococcus pyogenes / physiology*
  • Virulence


  • Antigens, Bacterial
  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • Carrier Proteins
  • Recombinant Fusion Proteins
  • streptococcal M protein
  • Plasminogen