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

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

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Kinetochores / metabolism
  • Mechanical Phenomena*
  • Microtubules / chemistry*
  • Microtubules / metabolism*
  • Protein Multimerization*
  • Tubulin / metabolism*

Substances

  • Tubulin