Analysis of plasminogen-binding M proteins of Streptococcus pyogenes.
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.
Ringdahl
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Institute for Laboratory Medicine, Section for Microbiology, Immunology and Glycobiology, Lund University, Sölvegatan 23, Lund, S-223 62, Sweden. Ulrika.Ringdahl@mig.lu.se
Sjöbring
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D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000032:analysis / Q000378:metabolism*; D001665:Binding Sites; D015153:Blotting, Western; D002352:Carrier Proteins / Q000032:analysis / Q000378:metabolism*; D003001:Cloning, Molecular; D004587:Electrophoresis, Agar Gel / Q000379:methods; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D006801:Humans; D010958:Plasminogen / Q000378:metabolism*; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000032:analysis / Q000378:metabolism; D013297:Streptococcus pyogenes / Q000472:pathogenicity* / Q000502:physiology*; D014774:Virulence
D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D011993:Recombinant Fusion Proteins; C014689:streptococcal M protein; D010958:Plasminogen