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Updated: Jun 28, 2026
Self-Assembly of Microtubule Tactoids
Published on: June 23, 2022
A kinesin-13 mutant catalytically depolymerizes microtubules in ADP
Michael Wagenbach1, Sarah Domnitz, Linda Wordeman
1Deptartment of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA 98107, USA.
Abstract:
The kinesin-13 motor protein family members drive the removal of tubulin from microtubules (MTs) to promote MT turnover. A point mutation of the kinesin-13 family member mitotic centromere-associated kinesin/Kif2C (E491A) isolates the tubulin-removal conformation of the motor, and appears distinct from all previously described kinesin-13 conformations derived from nucleotide analogues. The E491A mutant removes tubulin dimers from stabilized MTs stoichiometrically in adenosine triphosphate (ATP) but is unable to efficiently release from detached tubulin dimers to recycle catalytically. Only in adenosine diphosphate (ADP) can the mutant catalytically remove tubulin dimers from stabilized MTs because the affinity of the mutant for detached tubulin dimers in ADP is low relative to lattice-bound tubulin. Thus, the motor can regenerate for further cycles of disassembly. Using the mutant, we show that release of tubulin by kinesin-13 motors occurs at the transition state for ATP hydrolysis, which illustrates a significant divergence in their coupling to ATP turnover relative to motile kinesins.
Insights
Kinesin-13 motors, like mitotic centromere-associated kinesin, remove tubulin from microtubules. A specific mutation reveals tubulin removal occurs at the ATP hydrolysis transition state, differing from other kinesins.
Area of Science:
- Biochemistry
- Cell Biology
- Molecular Motors
Background:
- Kinesin-13 family motor proteins are crucial for microtubule (MT) dynamics by promoting tubulin removal.
- Microtubule turnover is essential for various cellular processes, including cell division and intracellular transport.
Purpose of the Study:
- To investigate the mechanism of tubulin dimer removal by kinesin-13 motors.
- To characterize the unique conformation and catalytic cycle of a specific kinesin-13 mutant (E491A).
- To elucidate the relationship between ATP hydrolysis and tubulin release in kinesin-13 function.
Main Methods:
- Utilized a point mutant (E491A) of the kinesin-13 family member mitotic centromere-associated kinesin/Kif2C.
- Studied tubulin dimer removal from stabilized microtubules in the presence of adenosine triphosphate (ATP) and adenosine diphosphate (ADP).
- Analyzed the catalytic cycle and tubulin binding affinity of the mutant motor.
Main Results:
- The E491A mutant isolates a distinct tubulin-removal conformation of kinesin-13.
- Tubulin removal by the mutant is stoichiometric in ATP but catalytic only in ADP due to altered tubulin dimer release kinetics.
- The motor regenerates catalytically in ADP, enabling further cycles of microtubule disassembly.
Conclusions:
- Kinesin-13 mediated tubulin release from microtubules occurs at the transition state of ATP hydrolysis.
- This mechanism represents a significant divergence in ATP turnover coupling compared to motile kinesins.
- The findings provide new insights into the regulation and function of microtubule-severing kinesins.
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