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Full-length dimeric MCAK is a more efficient microtubule depolymerase than minimal domain monomeric MCAK
Kathleen M Hertzer1, Stephanie C Ems-McClung, Susan L Kline-Smith
1Medical Sciences Program, Indiana University, Bloomington, IN 47405, USA.
Molecular Biology of the Cell
|November 18, 2005
Summary
Microtubule kinesin-13 (MCAK) dimerization enhances its microtubule depolymerization activity. Full-length MCAK dimers bind microtubule ends more efficiently and recycle better than monomeric units, preventing sequestration by tubulin.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- MCAK (Kinesin-13 family) is a microtubule depolymerase.
- Previous studies identified the minimal functional unit as the catalytic domain plus neck (MD-MCAK).
Purpose of the Study:
- To compare the activity of full-length MCAK (dimer) with MD-MCAK (monomer).
- To investigate the role of MCAK dimerization in its catalytic cycle and microtubule depolymerization.
Main Methods:
- Steady-state ATPase kinetics assays.
- Microtubule depolymerization assays.
- Microtubule-MCAK cosedimentation assays.
Main Results:
- Full-length MCAK dimers showed higher ATPase activity compared to monomeric MD-MCAK.
- Dimeric MCAK exhibited more efficient binding to microtubule ends.
- MCAK dimers had reduced affinity for tubulin heterodimers.
Conclusions:
- MCAK dimerization is crucial for its catalytic cycle.
- Dimerization promotes binding to microtubule ends and enhances recycling for multiple depolymerization rounds.
- Dimerization prevents MCAK sequestration by tubulin heterodimers.