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Multiple binding of type 3 streptococcal M protein to human fibrinogen, albumin and fibronectin
K H Schmidt1, K Mann, J Cooney
1Universität Jena, Institut für Experimentelle Mikrobiologie, FRG.
Abstract:
M proteins are major virulence factors of group A streptococci which enable the bacteria to resist phagocytic attack. Their binding capacity for different plasma proteins seems to be one reason for the antiphagocytic activity of M protein. In the present study we demonstrate that M3 protein, isolated from the streptococcal culture supernatant of strain 4/55, and the recombinant form (rM3), purified from an E. coli lysate after cloning in phage lambda-EMBL3, show a multiple binding to fibrinogen, albumin and fibronectin in Western blot and dot binding assays. Binding of M3 protein to the multifunctional extracellular matrix and plasma protein fibronectin may not only influence phagocytosis but may also contribute to the adherence of these bacteria to endothelial and epithelial cells.
Insights
Group A streptococci M proteins, like M3, bind plasma proteins such as fibrinogen, albumin, and fibronectin. This binding contributes to the bacteria
Area of Science:
- Microbiology
- Immunology
- Molecular Biology
Background:
- M proteins are key virulence factors for group A streptococci.
- Their role in resisting phagocytosis is linked to plasma protein binding.
Purpose of the Study:
- To investigate the binding capabilities of M3 protein.
- To understand how M3 protein interactions influence bacterial virulence.
Main Methods:
- Isolation of M3 protein from streptococcal culture supernatant.
- Purification of recombinant M3 protein (rM3) from E. coli lysate.
- Western blot and dot binding assays to assess protein interactions.
Main Results:
- M3 protein and rM3 demonstrated multiple binding affinities.
- Specific binding observed for fibrinogen, albumin, and fibronectin.
- Fibronectin binding may impact both phagocytosis and bacterial adherence.
Conclusions:
- M3 protein exhibits broad plasma protein binding, contributing to antiphagocytic properties.
- Interaction with fibronectin is significant for bacterial adherence to host cells.
- M3 protein's multifunctional binding enhances group A streptococcal virulence.