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Elife. 2017 Jun 19;6. pii: e28433. doi: 10.7554/eLife.28433.

Direct measurement of conformational strain energy in protofilaments curling outward from disassembling microtubule tips.

Author information

1
Department of Physiology and Biophysics, University of Washington, Seattle, United States.
2
Department of Biophysics, UT Southwestern Medical Center, Dallas, United States.
3
Department of Biochemistry, UT Southwestern Medical Center, Dallas, United States.

Abstract

Disassembling microtubules can generate movement independently of motor enzymes, especially at kinetochores where they drive chromosome motility. A popular explanation is the 'conformational wave' model, in which protofilaments pull on the kinetochore as they curl outward from a disassembling tip. But whether protofilaments can work efficiently via this spring-like mechanism has been unclear. By modifying a previous assay to use recombinant tubulin and feedback-controlled laser trapping, we directly demonstrate the spring-like elasticity of curling protofilaments. Measuring their mechanical work output suggests they carry ~25% of the energy of GTP hydrolysis as bending strain, enabling them to drive movement with efficiency similar to conventional motors. Surprisingly, a β-tubulin mutant that dramatically slows disassembly has no effect on work output, indicating an uncoupling of disassembly speed from protofilament strain. These results show the wave mechanism can make a major contribution to kinetochore motility and establish a direct approach for measuring tubulin mechano-chemistry.

KEYWORDS:

S. cerevisiae; biophysics; cell biology; kinetochore; laser trap; mechanochemistry; mitosis; optical tweezer; ram's horn; structural biology

PMID:
28628007
PMCID:
PMC5515574
DOI:
10.7554/eLife.28433
[Indexed for MEDLINE]
Free PMC Article

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