Single-molecule scale quantification reveals interactions underlying protein-protein interface: from forces to...

Area of Science:

• Biophysics
• Molecular Biology
• Cell Signaling

Background:

• Protein-protein interactions (PPIs) within the B-cell lymphoma 2 (Bcl-2) family are critical for cell cycle regulation and signaling pathways.
• The precise molecular mechanisms underlying these interfacial noncovalent interactions remain largely unelucidated.

Purpose of the Study:

• To investigate the molecular interactions between the anti-apoptotic protein Bcl-2 and the pro-apoptotic protein BAX.
• To elucidate the physical forces and binding kinetics governing the BAX/Bcl-2 complex formation.

Main Methods:

• Atomic force microscopy-based single-molecule force spectroscopy (SMFS) was employed to probe BAX/Bcl-2 interactions at the single-molecule level.
• Advanced analytical models, including kinetic, thermodynamic, Poisson distribution, and contact angle molecular recognition models, were utilized for comprehensive analysis.

Main Results:

• The study identified that both specific forces (hydrogen bonding) and non-specific forces (hydrophobic and electrostatic interactions) mediate the binding kinetics between BAX and Bcl-2.
• Complex multivalent binding interactions were shown to induce stable BAX/Bcl-2 complexes.
• This work provides the first direct experimental insights into the BAX/Bcl-2 interaction interface.

Conclusions:

• The findings enhance the understanding of the molecular mechanisms governing BAX-Bcl-2 interactions.
• The study offers valuable insights into the physical factors relevant for designing novel protein-protein interaction inhibitors.