5M5O image
Entry Detail
PDB ID:
5M5O
Keywords:
Title:
Pseudo-atomic model of microtubule-bound S.pombe kinesin-5 motor domain in the AMPPNP state (based on cryo-electron microscopy experiment): the N-terminus adopts multiple conformations.
Biological Source:
PDB Version:
Deposition Date:
2016-10-22
Release Date:
2016-11-30
Method Details:
Experimental Method:
Resolution:
9.30 Å
Aggregation State:
HELICAL ARRAY
Reconstruction Method:
SINGLE PARTICLE
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:Tubulin alpha-1D chain
Chain IDs:A
Chain Length:452
Number of Molecules:1
Biological Source:Bos taurus
Polymer Type:polypeptide(L)
Description:Tubulin beta-2B chain
Chain IDs:B
Chain Length:445
Number of Molecules:1
Biological Source:Bos taurus
Polymer Type:polypeptide(L)
Description:Kinesin-like protein cut7
Chain IDs:C
Chain Length:369
Number of Molecules:1
Biological Source:Schizosaccharomyces pombe (strain 972 / ATCC 24843)
Primary Citation
Schizosaccharomyces pombe kinesin-5 switches direction using a steric blocking mechanism.
Proc. Natl. Acad. Sci. U.S.A. 113 E7483 E7489 (2016)
PMID: 27834216 DOI: 10.1073/pnas.1611581113

Abstact

Cut7, the sole kinesin-5 in Schizosaccharomyces pombe, is essential for mitosis. Like other yeast kinesin-5 motors, Cut7 can reverse its stepping direction, by mechanisms that are currently unclear. Here we show that for full-length Cut7, the key determinant of stepping direction is the degree of motor crowding on the microtubule lattice, with greater crowding converting the motor from minus end-directed to plus end-directed stepping. To explain how high Cut7 occupancy causes this reversal, we postulate a simple proximity sensing mechanism that operates via steric blocking. We propose that the minus end-directed stepping action of Cut7 is selectively inhibited by collisions with neighbors under crowded conditions, whereas its plus end-directed action, being less space-hungry, is not. In support of this idea, we show that the direction of Cut7-driven microtubule sliding can be reversed by crowding it with non-Cut7 proteins. Thus, crowding by either dynein microtubule binding domain or Klp2, a kinesin-14, converts Cut7 from net minus end-directed to net plus end-directed stepping. Biochemical assays confirm that the Cut7 N terminus increases Cut7 occupancy by binding directly to microtubules. Direct observation by cryoEM reveals that this occupancy-enhancing N-terminal domain is partially ordered. Overall, our data point to a steric blocking mechanism for directional reversal through which collisions of Cut7 motor domains with their neighbors inhibit their minus end-directed stepping action, but not their plus end-directed stepping action. Our model can potentially reconcile a number of previous, apparently conflicting, observations and proposals for the reversal mechanism of yeast kinesins-5.

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