Load-dependent Release Limits the Processive Stepping of the Tetrameric Eg5 Motor

Eur Biophys J. 2007 Jul;36(6):675-81. doi: 10.1007/s00249-007-0134-6. Epub 2007 Feb 28.


Tetrameric motor proteins of the Kinesin-5 family are essential for eukaryotic cell division. The microscopic mechanism by which Eg5, the vertebrate Kinesin-5, drives bipolar mitotic spindle formation remains unknown. Here we show in optical trapping experiments that full-length Eg5 moves processively and stepwise along microtubule bundles. Interestingly, the force produced by individual Eg5 motors typically reached only approximately 2 pN, one-third of the stall force of Kinesin-1. Eg5 typically detached from microtubules before stalling. This behavior may reflect a regulatory mechanism important for the role of Eg5 in the mitotic spindle.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Kinesin / chemistry
  • Kinesin / physiology*
  • Microtubules / chemistry
  • Microtubules / physiology*
  • Motion
  • Optical Tweezers
  • Xenopus Proteins / chemistry
  • Xenopus Proteins / physiology*
  • Xenopus laevis


  • KIF11 protein, Xenopus
  • Xenopus Proteins
  • Kinesin