Streptococcus pyogenes fibronectin-binding protein F2: expression profile, binding characteristics, and impact on...

Area of Science:

• Microbiology
• Molecular Biology
• Infectious Diseases

Background:

• Some Streptococcus pyogenes (group A streptococci, GAS) strains express fibronectin-binding protein F2, distinct from protein F1/SfbI.
• Protein F2 plays a role in GAS adherence and invasion, particularly in superficial infections.

Purpose of the Study:

• To characterize the interaction of Streptococcus pyogenes protein F2 with fibronectin.
• To evaluate the contribution of protein F2 to GAS adherence, invasion, and virulence.

Main Methods:

• Recombinant protein F2 domains were used to assess binding kinetics with fibronectin fragments.
• Isogenic prtF2 mutant strains of GAS were constructed and analyzed for attachment and internalization.
• prtF2 gene transcription and protein F2 expression were monitored under different growth conditions.

Main Results:

• Protein F2's binding domains exhibit nanomolar affinity for fibronectin, primarily interacting with a 30-kDa fragment.
• prtF2 mutant strains showed significantly reduced attachment to fibronectin and HEp-2 cells, and decreased internalization.
• Protein F2 expression is maximal at the transition to the stationary phase, especially under aerobic conditions.

Conclusions:

• Protein F2 is a major fibronectin-binding adhesin in a subset of GAS strains.
• Protein F2 independently contributes to both bacterial attachment and internalization.
• Its expression pattern and specific fibronectin interaction suggest it is an essential virulence factor for GAS superficial infections.