Dynamics of a partially stretched protein molecule studied using an atomic force microscope.

Area of Science:

• Biophysics
• Protein Dynamics
• Mechanical Unfolding

Background:

• Bovine carbonic anhydrase II (BCA) exists in two conformational isomers: type I (enzymatically active) and type II (inactive).
• Understanding the mechanical properties and dynamic behavior of these isomers is crucial for protein folding studies.

Purpose of the Study:

• To investigate the mechanical unfolding dynamics of single bovine carbonic anhydrase II (BCA) molecules.
• To differentiate the dynamic responses of the two BCA conformers (type I and type II) under mechanical stress.

Main Methods:

• Utilized a custom-built atomic force microscope (AFM) for single-molecule force spectroscopy.
• Applied external oscillations to measure tensile force and mechanical response in the millisecond time domain.

Main Results:

• Type I BCA conformer displayed an out-of-phase response to external oscillation during mechanical extension.
• Type II BCA conformer consistently showed an in-phase response to external oscillation.
• These distinct dynamical behaviors were observed near the transition point between type I and type II conformations.

Conclusions:

• The mechanical unfolding dynamics of BCA isomers are conformation-dependent.
• AFM-based dynamic measurements can distinguish between active and inactive BCA conformers.
• This study provides insights into protein conformational transitions under mechanical force.