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Nat Commun. 2015 Oct 6;6:8160. doi: 10.1038/ncomms9160.

Kinesin-5 is a microtubule polymerase.

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Department of Biomedical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Interdisciplinary Graduate Degree Program in Cell and Developmental Biology, Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.


Kinesin-5 slides antiparallel microtubules during spindle assembly, and regulates the branching of growing axons. Besides the mechanical activities enabled by its tetrameric configuration, the specific motor properties of kinesin-5 that underlie its cellular function remain unclear. Here by engineering a stable kinesin-5 dimer and reconstituting microtubule dynamics in vitro, we demonstrate that kinesin-5 promotes microtubule polymerization by increasing the growth rate and decreasing the catastrophe frequency. Strikingly, microtubules growing in the presence of kinesin-5 have curved plus ends, suggesting that the motor stabilizes growing protofilaments. Single-molecule fluorescence experiments reveal that kinesin-5 remains bound to the plus ends of static microtubules for 7 s, and tracks growing microtubule plus ends in a manner dependent on its processivity. We propose that kinesin-5 pauses at microtubule plus ends and enhances polymerization by stabilizing longitudinal tubulin-tubulin interactions, and that these activities underlie the ability kinesin-5 to slide and stabilize microtubule bundles in cells.

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