Journal
JOURNAL OF CELL BIOLOGY
Volume 197, Issue 7, Pages 957-970Publisher
ROCKEFELLER UNIV PRESS
DOI: 10.1083/jcb.201201132
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Funding
- National Institutes of Health [GM086351, GM54141, P41-RR000592]
- U.S. Department of Energy, Office of Energy Research [W-31-109-ENG-38]
- NIH [T32-GM07215, T32-GM065103]
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Kinesin-14 motors generate microtubule minus-end-directed force used in mitosis and meiosis. These motors are dimeric and operate with a nonprocessive powerstroke mechanism, but the role of the second head in motility has been unclear. In Saccharomyces cerevisiae, the Kinesin-14 Kar3 forms a heterodimer with either Vik1 or Cik1. Vik1 contains a motor homology domain that retains microtubule binding properties but lacks a nucleotide binding site. In this case, both heads are implicated in motility. Here, we show through structural determination of a C-terminal heterodimeric Kar3Vik1, electron microscopy, equilibrium binding, and motility that at the start of the cycle, Kar3Vik1 binds to or occludes two alpha beta-tubulin subunits on adjacent protofilaments. The cycle begins as Vik1 collides with the microtubule followed by Kar3 microtubule association and ADP release, thereby destabilizing the Vik1-microtubule interaction and positioning the motor for the start of the powerstroke. The results indicate that head-head communication is mediated through the adjoining coiled coil.
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