Structural model for tubulin recognition and deformation by kinesin-13 microtubule depolymerases

Area of Science:

• Biochemistry
• Structural Biology
• Cell Biology

Background:

• Microtubules are dynamic polymers essential for cell division and structure.
• Kinesin-13 motor proteins are unique in their ability to depolymerize microtubules, a process crucial for cellular regulation.
• The precise mechanism by which kinesin-13s interact with and destabilize microtubules remains incompletely understood.

Purpose of the Study:

• To elucidate the structural basis of microtubule depolymerization mediated by kinesin-13 motor proteins.
• To determine the high-resolution structure of a kinesin-13 motor bound to tubulin.

Main Methods:

• Cryo-electron microscopy (cryo-EM) to obtain a 1.1 nm resolution 3D structure.
• Fluorescence polarization microscopy to analyze protein interactions.
• Biochemical assays involving site-directed mutagenesis.

Main Results:

• A high-resolution cryo-EM structure of the KLP10A head domain (KLP10AHD) bound to curved tubulin was determined.
• KLP10AHD binding induces tubulin curvature and subunit shear, creating a distinct configuration.
• The KLP10AHD-tubulin interface involves three interaction sites, including conserved KVD residues, suggesting a crossbow-like bending mechanism.
• Mutating KVD residues altered KLP10AHD orientation and mobility on microtubules.

Conclusions:

• The study reveals a novel crossbow-type mechanism for tubulin bending by kinesin-13s.
• This mechanism explains the distinct binding modes of kinesin-13s to microtubule lattice and ends.
• Structural insights into KLP10AHD-tubulin interactions provide a foundation for understanding microtubule dynamics regulation.