AFM Identifies a Protein Complex Involved in Pathogen Adhesion Which Ruptures at Three Nanonewtons

Area of Science:

• Molecular Biology
• Biophysics
• Infectious Diseases

Background:

• Staphylococci infections can cause endovascular infections through binding to von Willebrand Factor (vWF).
• The specific interaction mechanism between Staphylococcus epidermidis and vWF remains largely unknown.

Purpose of the Study:

• To investigate the binding mechanism between the Staphylococcus epidermidis protein Aap and von Willebrand Factor (vWF).
• To explore the potential of this interaction for developing novel antistaphylococcal therapies.

Main Methods:

• Utilized single-molecule experiments to analyze Aap-vWF binding.
• Employed inhibition assays with specific monoclonal antibodies to identify involved protein domains.
• Investigated the role of tensile loading and force in the binding interaction.

Main Results:

• Demonstrated an ultrastrong noncovalent bond (∼3 nN) between Aap and vWF, the strongest reported.
• Identified Aap-vWF binding as a force-activated process, exhibiting catch-bond behavior.
• Pinpointed the vWF A1 domain and both A and B domains of Aap as critical for binding.

Conclusions:

• Proposed a mechanism involving force-induced unfolding of Aap's B repeats, activating its A domain for ultrastrong vWF A1 binding.
• Highlighted the shear-dependent function of Aap as a promising target for innovative antistaphylococcal therapies.