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bioRxiv · 10.1101/141978

Single molecule mechanics reveal Kif15 as an active molecular ratchet with acute strain sensitivity

McHugh, T.·Drechsler, H.·McAinsh, A. D.·Carter, N. J.·Cross, R. A.
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Abstract

Human Kif15 is a tetrameric kinesin-12 that contributes critically to bipolar spindle assembly in eukaryotes. Here we examine its single molecule mechanics. Under hindering loads, Kif15 steps predominantly towards microtubule plus ends, with its forestep:backstep ratio decreasing exponentially with load and stall occurring at ~6pN. Between steps, Kif15 binds stably, usually via a single head domain. By complete contrast, under assisting loads, Kif15 detaches rapidly, even in AMPPNP. Furthermore, Kif15 can autoinhibit, via an interaction requiring its C-terminus. Autoinhibited Kif15 binds microtubules nucleotide-independently, resists both hindering and assisting loads, and is further stabilized by Tpx2, which interacts with the Kif15 C-terminus. Our data reveal the mechanics of Kif15 to be extraordinarily sensitive to loading direction. When unloaded, it walks rapidly; when pulled forwards it slips and when pulled backwards it grips. We discuss the implications of this unique mechanical behaviour for the roles of Kif15 in spindle function.

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McHugh, T., Drechsler, H., McAinsh, A. D., Carter, N. J., Cross, R. A.. 2017-05-25. Single molecule mechanics reveal Kif15 as an active molecular ratchet with acute strain sensitivity. https://doi.org/10.1101/141978

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