A kinesin-13 mutant catalytically depolymerizes microtubules in ADP

“…Wagenbach et al . propose that there are two transition states that MCAK goes through for MT depolymerization prior to ATP hydrolysis: high affinity end binding and tubulin detachment from the MT [33]. The MCAK conformational changes we show in this study likely correlate with these different nucleotide and MT binding states (Figure 7A).…”

Section: Discussionmentioning

confidence: 56%

Aurora B Inhibits MCAK Activity through a Phosphoconformational Switch that Reduces Microtubule Association

et al. 2013

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SUMMARY Background Proper spindle assembly and chromosome segregation relies on precise microtubule dynamics, which are governed in part by the Kinesin-13 MCAK. MCAK microtubule depolymerization activity is inhibited by Aurora B-dependent phosphorylation, but the mechanism of this inhibition is not understood. Results Here we develop the first FRET-based biosensor for MCAK and show that MCAK in solution exists in a closed conformation mediated by an interaction between the C-terminal domain (CT) and the neck. Using fluorescence lifetime imaging (FLIM) we show that MCAK bound to microtubule ends is closed relative to MCAK associated with the microtubule lattice. Aurora B phosphorylation at S196 in the neck opens MCAK conformation and diminishes the interaction between the CT and the neck. Using FLIM and TIRF imaging we found that changes in MCAK conformation are associated with a decrease in MCAK affinity for the microtubule. Conclusions Unlike motile kinesins, which are open when doing work, the high affinity binding state for microtubule depolymerizing kinesins is in a closed conformation. Phosphorylation switches MCAK conformation, which inhibits its ability to interact with microtubules and reduces its microtubule depolymerization activity. This work shows that the conformational model proposed for regulating kinesin activity is not universal and that microtubule depolymerizing kinesins utilize a distinct conformational mode to regulate affinity for the microtubule, thus controlling their catalytic efficiency. Furthermore, our work provides a mechanism by which the robust microtubule depolymerization activity of Kinesin-13s can be rapidly modulated to control cellular microtubule dynamics.

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“…Once at the end, MCAK promotes disassembly through a high affinity interaction with curved tubulin which stimulates its ATPase activity, enabling it to recycle for additional rounds of catalysis. (Hunter et al, 2003; Wagenbach et al, 2008). …”

Section: Discussionmentioning

confidence: 99%

A Tubulin Binding Switch Underlies Kip3/Kinesin-8 Depolymerase Activity

et al. 2017

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Summary Kinesin-8 motors regulate the size of microtubule structures, using length-dependent accumulation at the plus-end to preferentially disassemble long microtubules. Despite extensive study, the kinesin-8 depolymerase mechanism remains under debate. Here, we provide evidence for an alternative, tubulin curvature-sensing model of microtubule depolymerization by the budding yeast kinesin-8, Kip3. Kinesin-8/Kip3 uses ATP hydrolysis, like other kinesins, for stepping on the microtubule lattice, but at the plus-end, Kip3 undergoes a switch: Its ATPase activity is suppressed when it binds tightly to the curved conformation of tubulin. This prolongs plus-end binding, stabilizes protofilament curvature, and ultimately promotes microtubule disassembly. The tubulin curvature-sensing model is supported by our identification of Kip3 structural elements necessary and sufficient for plus-end binding and depolymerase activity, as well as by the identification of an α-tubulin residue specifically required for the Kip3-curved tubulin interaction. Together, these findings elucidate a major regulatory mechanism controlling the size of cellular microtubule structures.

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A kinesin-13 mutant catalytically depolymerizes microtubules in ADP

Cited by 31 publications

References 31 publications

Prime movers: the mechanochemistry of mitotic kinesins

Prime movers: the mechanochemistry of mitotic kinesins

Aurora B Inhibits MCAK Activity through a Phosphoconformational Switch that Reduces Microtubule Association

A Tubulin Binding Switch Underlies Kip3/Kinesin-8 Depolymerase Activity

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