Analysis of plasminogen-binding M proteins of Streptococcus pyogenes |
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Authors: | Ringdahl U Sjöbring U |
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Institution: | Institute for Laboratory Medicine, Section for Microbiology, Immunology and Glycobiology, Lund University, S?lvegatan 23, Lund, S-223 62, Sweden. Ulrika.Ringdahl@mig.lu.se |
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Abstract: | 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. |
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