Detection of fractional steps in cargo movement by the collective operation of kinesin-1 motors

Research output: Contribution to journalResearch articleContributedpeer-review


  • Cécile Leduc - , Max Planck Institute of Molecular Cell Biology and Genetics (Author)
  • Felix Ruhnow - , Max Planck Institute of Molecular Cell Biology and Genetics (Author)
  • Jonathon Howard - , Max Planck Institute of Molecular Cell Biology and Genetics (Author)
  • Stefan Diez - , Max Planck Institute of Molecular Cell Biology and Genetics (Author)


The stepping behavior of single kinesin-1 motor proteins has been studied in great detail. However, in cells, these motors often do not work alone but rather function in small groups when they transport cellular cargo. Until now, the cooperative interactions between motors in such groups were poorly understood. A fundamental question is whether two or more motors that move the same cargo step in synchrony, producing the same step size as a single motor, or whether the step size of the cargo movement varies. To answer this question, we performed in vitro gliding motility assays, where microtubules coated with quantum dots were driven over a glass surface by a known number of kinesin-1 motors. The motion of individual microtubules was then tracked with nanometer precision. In the case of transport by two kinesin-1 motors, we found successive 4-nm steps, corresponding to half the step size of a single motor. Dwell-time analysis did not reveal any coordination, in the sense of alternate stepping, between the motors. When three motors interacted in collective transport, we identified distinct forward and backward jumps on the order of 10 nm. The existence of the fractional steps as well as the distinct jumps illustrate a lack of synchronization and has implications for the analysis of motor-driven organelle movement investigated in vivo.


Original languageEnglish
Pages (from-to)10847-10852
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America : PNAS
Issue number26
Publication statusPublished - 26 Jun 2007
Externally publishedYes

External IDs

PubMed 17569782
ORCID /0000-0002-0750-8515/work/142235580


ASJC Scopus subject areas


  • Collective motion, Microtubules, Nanometer tracking, Quantum dots