Kinesin is a molecular motor that moves processively1-4 by regular 8-nm steps along microtubules5-11. The processivity of this movement is explained by a hand-over-hand model in which the two heads of kinesin work in a coordinated manner. One head remains bound to the microtubule while the other steps from the αβ-tubulin dimer behind the attached head to the dimer in front. The overall movement is 8 nm per ATPase cycle9-13. To investigate elementary processes within the 8-nm step, we have developed a new assay that resolves nanometre displacements of single kinesin molecules with microsecond accuracy. Our data show that the 8-nm step can be resolved into fast and show substeps, each corresponding to a displacement of Ο4 nm. The substeps are most probably generated by structural changes in one head of kinesin, leading to rectified forward thermal motions of the partner head14. It is also possible that the kinesin steps along the 4-nm repeat of tubulin monomers.
ASJC Scopus subject areas
- Cell Biology