The strongest protein binder is surprisingly labile

Area of Science:

• Microbiology
• Biophysics
• Molecular Biology

Background:

• Bacterial adhesins mediate host cell attachment, initiating infections.
• Microbial surface components recognizing adhesive matrix molecules (MSCRAMMs), like Staphylococcus aureus ClfA, bind host proteins such as fibrinogen (Fg).
• MSCRAMMs exhibit catch-bond behavior, withstanding high forces, but the intrinsic strength of the adhesin itself is unclear.

Purpose of the Study:

• To investigate the intrinsic mechanical strength of the Staphylococcus aureus adhesin, clumping factor A (ClfA).
• To determine if the observed high mechanical strength of ClfA-Fg interactions originates from ClfA alone or the interaction.

Main Methods:

• Single-molecule force spectroscopy to measure bond rupture forces.
• Biophysical binding assays to quantify interaction strength.
• Molecular simulations to model protein behavior and interactions.

Main Results:

• ClfA-Fg interactions withstand forces exceeding 2 nN, mimicking covalent bonds.
• Despite the strong interaction, ClfA alone does not possess exceptional intrinsic mechanical strength.
• The mechanical stability is attributed to the specific ClfA-Fg interaction rather than ClfA's inherent properties.

Conclusions:

• The remarkable mechanical strength of ClfA-Fg binding is a feature of the interaction, not solely the adhesin.
• Understanding these contributions is crucial for developing anti-adhesion strategies against bacterial infections.
• This research provides insights into the biophysics of bacterial adhesion and host-pathogen interactions.