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bioRxiv · 10.1101/520072

Kinesin-5 promotes microtubule nucleation and assembly by stabilizing a lattice-competent conformation of tubulin

Chen, G.-Y.·Asenjo, A. B.·Chen, Y.·Mascaro, J.·Arginteanu, D. F. J.·Sosa, H. J.·Hancock, W. O.
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Abstract

Besides sliding apart antiparallel microtubules during spindle elongation, the mitotic kinesin-5, Eg5 promotes microtubule polymerization, emphasizing its importance in mitotic spindle length control. Here, we characterize the Eg5 microtubule polymerase mechanism by assessing motor-induced changes in the longitudinal and lateral tubulin-tubulin bonds that form the microtubule lattice. Isolated Eg5 motor domains promote microtubule nucleation, growth and stability. Eg5 binds preferentially to microtubules over free tubulin, and colchicine-like inhibitors that stabilize the bent conformation of tubulin allosterically inhibit Eg5 binding, consistent with a model in which Eg5 induces a curved-to-straight transition in tubulin. Domain swap experiments establish that the family-specific Loop11, which resides near the nucleotide-sensing Switch-II domain, is necessary and sufficient for the polymerase activity of Eg5. Thus, we propose a microtubule polymerase mechanism in which Eg5 at the plus-end promotes a curved-to-straight transition in tubulin that enhances lateral bond formation and thereby promotes microtubule growth and stability.

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Chen, G.-Y., Asenjo, A. B., Chen, Y., Mascaro, J., Arginteanu, D. F. J., Sosa, H. J., Hancock, W. O.. 2019-01-14. Kinesin-5 promotes microtubule nucleation and assembly by stabilizing a lattice-competent conformation of tubulin. https://doi.org/10.1101/520072

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