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The SpeB virulence factor of Streptococcus pyogenes, a multifunctional secreted and cell surface molecule with
J Hytönen1, S Haataja, D Gerlach
1Department of Medical Biochemistry and Molecular Biology, University of Turku, Kiinamyllynkatu 10, FIN-20520 Turku, Finland. jukka.hytonen@utu.fi
Abstract:
The interactions between pathogenic bacteria and the host need to be resolved at the molecular level in order to develop novel vaccines and drugs. We have previously identified strepadhesin, a novel glycoprotein-binding activity in Streptococcus pyogenes, which is regulated by Mga, a regulator of streptococcal virulence factors. We have now identified the protein responsible for the strepadhesin activity and find that (i) strepadhesin activity is carried by SpeB, streptococcal pyrogenic exotoxin with cysteine protease activity; (ii) SpeB carries laminin-binding activity of the bacteria; and (iii) SpeB is not only a secreted molecule but also occurs unexpectedly tightly bound to the bacterial cell surface. Thus, in contrast to the previous view of SpeB as mainly an extracellular protease, it is also present as a streptococcal surface molecule with binding activity to laminin and other glycoproteins.
Insights
Streptococcus pyogenes SpeB protein binds to host glycoproteins like laminin. This surface-bound SpeB challenges previous views, offering new targets for vaccines and drugs against bacterial infections.
Area of Science:
- Microbiology
- Molecular Biology
- Immunology
Background:
- Understanding pathogenic bacteria-host interactions is crucial for developing new vaccines and drugs.
- Streptococcus pyogenes possesses a glycoprotein-binding activity called strepadhesin, regulated by the Mga virulence factor.
Purpose of the Study:
- To identify the protein responsible for strepadhesin activity in Streptococcus pyogenes.
- To characterize the role and localization of this protein in bacterial pathogenesis.
Main Methods:
- Biochemical assays to identify the protein mediating strepadhesin activity.
- Characterization of the identified protein's enzymatic and binding properties.
- Analysis of the protein's localization on the bacterial cell surface.
Main Results:
- Streptococcal pyrogenic exotoxin (SpeB), a cysteine protease, was identified as the protein responsible for strepadhesin activity.
- SpeB mediates the binding of Streptococcus pyogenes to laminin and other host glycoproteins.
- SpeB is found not only secreted but also unexpectedly tightly bound to the bacterial cell surface.
Conclusions:
- SpeB functions as a surface-exposed molecule on Streptococcus pyogenes, in addition to its previously known extracellular protease role.
- The surface localization and laminin-binding activity of SpeB present novel therapeutic and vaccine targets for treating Streptococcus pyogenes infections.