A new model for binding of kinesin 13 to curved microtubule protofilaments

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Kinesin motor proteins are essential for intracellular transport.
• Most kinesins are processive motors that move along microtubules (MTs).
• Class 13 kinesins are unique, targeting MT ends for depolymerization.

Purpose of the Study:

• To elucidate the molecular mechanisms of kinesin-13 mediated MT depolymerization.
• To understand how kinesin-13 interacts with MT ends at a structural level.

Main Methods:

• Electron microscopy (EM) was used to visualize protein-MT interactions.
• Different kinesin-13 constructs (motor domain, neck+motor, full-length) were analyzed.
• Binding sites and structural conformations were mapped.

Main Results:

• Kinesin-13 motor domain binds to every tubulin heterodimer.
• Neck+motor and full-length constructs bind to alternate sites.
• Only one motor head is visible in dimeric full-length kinesin-13, suggesting steric hindrance by the neck region.
• Full-length kinesin-13 promotes increased tubulin ring stacking.

Conclusions:

• The neck region of kinesin-13 likely obstructs access to adjacent binding sites.
• A model is proposed where kinesin-13 binds to adjacent protofilaments for efficient depolymerization.
• This binding mechanism enhances the efficiency of microtubule disassembly.