Direction Matters: Monovalent Streptavidin/Biotin Complex under Load

Area of Science:

• Biophysics
• Biochemistry
• Materials Science

Background:

• The biotin/streptavidin complex is a widely used tool in molecular biology and biotechnology.
• Understanding its mechanical properties under force is crucial for various applications.
• Previous studies reported a wide range of rupture forces, suggesting variability in experimental conditions.

Purpose of the Study:

• To investigate the influence of force application geometry on the mechanical stability of the monovalent biotin/streptavidin complex.
• To elucidate the underlying mechanisms of unbinding using a combination of experimental and computational approaches.
• To reconcile the diverse rupture forces reported in the literature.

Main Methods:

• Single-molecule force spectroscopy using atomic force microscopy (AFM).
• Site-specific tethering strategies for precise control over complex orientation.
• Steered molecular dynamics (SMD) simulations.
• Machine learning techniques to analyze simulation data.

Main Results:

• Mechanical stability of the biotin/streptavidin complex is highly sensitive to the geometry of force application.
• Unbinding forces for C-terminal tethered monovalent streptavidin were significantly higher (beyond 400 pN at 10 nN/s loading rate) than for N-terminal tethering.
• SMD simulations revealed distinct force propagation pathways and identified partial unfolding of the streptavidin N-terminal region prior to biotin release, depending on the force geometry.

Conclusions:

• The geometry of force application is a critical determinant of the biotin/streptavidin complex's rupture force.
• Site-specific attachment and advanced computational methods provide deeper insights into complex mechanics.
• Findings necessitate a re-evaluation of previously reported rupture force data for this system.