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Adherence of Streptococcus pneumoniae to immobilized fibronectin
M van der Flier1, N Chhun, T M Wizemann
1Laboratory of Molecular Infectious Diseases, Rockefeller University, New York, New York 10021, USA.
Abstract:
Adherence to extracellular matrix proteins, such as fibronectin, affords pathogens with a mechanism to invade injured epithelia. Streptococcus pneumoniae was found to adhere to immobilized fibronectin more avidly than other streptococci and staphylococci do. Binding was dose, time, and temperature dependent. Trypsin treatment of the bacteria resulted in decreased binding, suggesting that the bacterial adhesive component was a protein. Fragments of fibronectin generated by proteolysis or by expression of recombinant gene segments were compared for the ability to bind pneumococci and to compete against bacterial binding to immobilized fibronectin. Fragments from the carboxy-terminal heparin binding domain were consistently active, suggesting that this region contains the pneumococcal binding site, a region distinct from that supporting the attachment of most other bacteria.
Insights
Streptococcus pneumoniae binds avidly to fibronectin, a protein found in injured tissues. This adherence, mediated by bacterial proteins, utilizes a specific site within fibronectin
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Pathogens like Streptococcus pneumoniae invade tissues by adhering to extracellular matrix proteins.
- Fibronectin is a key extracellular matrix protein involved in cellular adhesion and tissue repair.
Purpose of the Study:
- To investigate the adherence mechanism of Streptococcus pneumoniae to fibronectin.
- To identify the specific region on fibronectin responsible for pneumococcal binding.
Main Methods:
- Quantifying bacterial adherence to immobilized fibronectin under varying conditions (dose, time, temperature).
- Assessing the effect of bacterial proteinase treatment on fibronectin binding.
- Mapping pneumococcal binding sites on fibronectin using proteolysis and recombinant protein fragments.
Main Results:
- Streptococcus pneumoniae exhibited significantly higher avid adherence to fibronectin compared to other bacteria.
- Bacterial adherence was dependent on dose, time, and temperature, and was inhibited by trypsin treatment, indicating a proteinaceous bacterial adhesin.
- The carboxy-terminal heparin-binding domain of fibronectin was identified as the primary binding site for Streptococcus pneumoniae.
Conclusions:
- Streptococcus pneumoniae utilizes a specific protein adhesin to bind to the carboxy-terminal heparin-binding domain of fibronectin.
- This distinct binding mechanism facilitates pneumococcal invasion of injured epithelial tissues.