Structure of the kinesin13-microtubule ring complex

Area of Science:

• Structural Biology
• Molecular Motors
• Cell Biology

Background:

• Microtubules are essential cytoskeletal polymers involved in cell division and intracellular transport.
• Kinesin13 is a unique kinesin family that promotes microtubule depolymerization, a critical process for dynamic instability.
• Understanding the mechanism of kinesin13-mediated depolymerization is crucial for comprehending microtubule dynamics.

Purpose of the Study:

• To elucidate the structural mechanism by which kinesin13 induces microtubule depolymerization.
• To determine the atomic interactions between the kinesin13 motor domain and microtubules.
• To identify key residues and binding sites involved in kinesin13-microtubule complex formation.

Main Methods:

• Cryo-electron microscopy (cryo-EM) to generate a 3D map of the kinesin13-microtubule ring complex.
• Image analysis and atomic model docking using crystal structures of tubulin and kinesin13 motor domain.
• Site-directed mutagenesis to investigate the function of identified tubulin-binding sites.

Main Results:

• A 3D atomic model of the kinesin13 motor domain bound to a curved tubulin protofilament was generated.
• Kinesin13 class-specific residues were found to stabilize tubulin curvature at the microtubule plus-end.
• A conserved tubulin-binding site on the kinesin13 motor domain was identified, and mutations disrupted ring complex formation.

Conclusions:

• The study provides a structural snapshot of kinesin13-induced microtubule depolymerization at near-atomic resolution.
• Kinesin13 stabilizes protofilament curvature, suggesting a mechanism for promoting depolymerization.
• The identified tubulin-binding site is critical for the formation of kinesin13-microtubule structures.