5M5L: 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

Citation:
Abstract
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.
PDB ID: 5M5LDownload
MMDB ID: 145292
PDB Deposition Date: 2016/10/21
Updated in MMDB: 2016/12
Experimental Method:
electron microscopy
Resolution: 9.3  Å
Source Organism:
Schizosaccharomyces pombe 972h-
Similar Structures:
Biological Unit for 5M5L: trimeric; determined by author
Molecular Components in 5M5L
Label Count Molecule
Proteins (3 molecules)
1
Tubulin Alpha-1d Chain(Gene symbol: TUBA1D)
Molecule annotation
1
Tubulin Beta-2b Chain(Gene symbol: TUBB2B)
Molecule annotation
1
Kinesin-like Protein Cut7(Gene symbol: cut7)
Molecule annotation
Chemicals (6 molecules)
1
2
2
1
3
1
4
1
5
1
* Click molecule labels to explore molecular sequence information.

Citing MMDB
.