Nanonewton forces between Staphylococcus aureus surface protein IsdB and vitronectin

Area of Science:

• Biophysics
• Microbiology
• Molecular Interactions

Background:

• Staphylococcal surface proteins exhibit strong interactions with ligands, sometimes rivalling covalent bonds.
• Vitronectin (Vn) is a crucial human blood protein known to interact with bacterial pathogens.

Purpose of the Study:

• To investigate the binding strength between Staphylococcus aureus iron-regulated surface determinant B (IsdB) and vitronectin (Vn).
• To determine the effect of mechanical tension and fluid shear stress on the IsdB-Vn interaction.

Main Methods:

• Single-molecule force spectroscopy to measure binding forces under mechanical tension.
• Flow experiments to assess bacterial adhesion under fluid shear stress.

Main Results:

• The IsdB-Vn interaction demonstrated unusually high binding strength, reaching up to 2000 pN at a loading rate of 10^5 pN s^-1.
• Mechanical tension significantly strengthened the IsdB-Vn bond.
• IsdB-mediated bacterial adhesion to Vn was enhanced by fluid shear stress.

Conclusions:

• The IsdB-Vn interaction is mechanically regulated, exhibiting catch-bond behavior.
• Stress-dependent binding of IsdB to Vn likely contributes to Staphylococcus aureus adhesion to host cells under physiological flow conditions.