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

• Main Authors: Jonathan W Driver, Elisabeth A Geyer, Megan E Bailey, Luke M Rice, Charles L Asbury
• Format: Article
• Language: English
• Published: eLife Sciences Publications Ltd 2017-06-01
• Series: eLife
• Subjects: mechanochemistry; kinetochore; ram's horn; laser trap; optical tweezer; mitosis
• Online Access: https://elifesciences.org/articles/28433

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.