A torque component present in mitotic kinesin Eg5 revealed by three-dimensional tracking

Area of Science:

• Cell biology
• Molecular motors
• Cytoskeleton dynamics

Background:

• Mitotic kinesin Eg5 is a homotetrameric motor protein crucial for cell division.
• Eg5 cross-links and slides microtubules, but its processivity is not well understood.

Purpose of the Study:

• To investigate the processivity of mitotic kinesin Eg5 during microtubule sliding.
• To directly visualize the motion of microtubules driven by Eg5.

Main Methods:

• Utilized three-dimensional tracking of a quantum dot attached to a microtubule.
• Employed a motility assay to observe microtubule sliding dynamics.
• Analyzed the corkscrew motion and rotational pitch of the sliding microtubule.

Main Results:

• Directly visualized the corkscrew motion of microtubules sliding along Eg5.
• Demonstrated that the rotational pitch of microtubule sliding serves as an indicator of motor processivity.
• Confirmed that two-headed Eg5 exhibits significantly lower processivity compared to two-headed kinesin-1.

Conclusions:

• The rotational pitch of microtubule sliding provides a novel method to assess motor protein processivity.
• Mitotic kinesin Eg5 is less processive than kinesin-1, impacting its role in mitosis.
• Understanding Eg5 processivity is key to comprehending its function in cell division mechanics.