Processive behaviour of kinesin observed using micro-fabricated cantilevers

Area of Science:

• Biophysics
• Molecular Biology
• Nanotechnology

Background:

• Accurate mechanical characterization of biomolecular motors demands high-resolution force sensors.
• Microscale sensors can introduce structural deformations in nanoscale motors due to thermal fluctuations.
• Existing methods lack simple solutions to mitigate these sensor-induced motor deformations.

Purpose of the Study:

• To develop a novel force sensor with minimal degrees of freedom for studying kinesin-1.
• To investigate the mechanical properties and movement mechanism of kinesin-1.
• To determine if kinesin-1 requires tail rotation for processive movement.

Main Methods:

• Utilized micro-fabricated cantilevers to create a single-degree-of-freedom force sensor.
• Achieved a low spring constant of 0.03 pN nm(-1) for high sensitivity.
• Constrained kinesin-1 cargo binding domain movement during processive runs.

Main Results:

• Measured a step size of 8.0 ± 0.4 nm for kinesin-1.
• Determined a maximal unloaded velocity of 820 ± 80 nm s(-1) at saturated ATP concentrations.
• Observed that the cantilever excluded cargo rotation, constraining movement to a straight line.

Conclusions:

• Kinesin-1 moves processively in a straight line along microtubules.
• The motor protein does not require tail rotation for its stepping mechanism.
• This study provides new insights into the mechanics of molecular motors.