期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 113, 期 47, 页码 E7483-E7489出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1611581113
关键词
Cut7; kinesin-5; bidirectional kinesin; mitotic kinesin; kinesin crowding
资金
- Biotechnology and Biological Sciences Research Council Grant [BB/H005137/1]
- Worldwide Cancer Research Grant [11-0261]
- BBSRC [BB/L014211/1, BB/L001993/1, BB/L00190X/1, BB/H005137/1] Funding Source: UKRI
- MRC [G0200542] Funding Source: UKRI
- Biotechnology and Biological Sciences Research Council [BB/L001993/1, BB/L014211/1, BB/L00190X/1, BB/H005137/1] Funding Source: researchfish
- Medical Research Council [G0200542] Funding Source: researchfish
- Wellcome Trust [103895/Z/14/Z] Funding Source: researchfish
- Worldwide Cancer Research [11-0261] Funding Source: researchfish
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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