Insight into the molecular mechanism of the multitasking kinesin-8 motor

Abstract

Members of the kinesin-8 motor class have the remarkable ability to both walk towards microtubule plus-ends and depolymerise these ends on arrival, thereby regulating microtubule length. To analyse how kinesin-8 multitasks, we studied the structure and function of the kinesin-8 motor domain. We determined the first crystal structure of a kinesin-8 and used cryo-electron microscopy to calculate the structure of the microtubule-bound motor. Microtubule-bound kinesin-8 reveals a new conformation compared with the crystal structure, including a bent conformation of the α4 relay helix and ordering of functionally important loops. The kinesin-8 motor domain does not depolymerise stabilised microtubules with ATP but does form tubulin rings in the presence of a non-hydrolysable ATP analogue. This shows that, by collaborating, kinesin-8 motor domain molecules can release tubulin from microtubules, and that they have a similar mechanical effect on microtubule ends as kinesin-13, which enables depolymerisation. Our data reveal aspects of the molecular mechanism of kinesin-8 motors that contribute to their unique dual motile and depolymerising functions, which are adapted to control microtubule length.

Prime movers: the mechanochemistry of mitotic kinesins

“…KIF18A can also make tubulin rings 113 and has an extended loop-2 reminiscent of the kinesin-13 family (BOX 2), which supports the idea that it can bend tubulin to drive depolymerization. These effects on microtubule dynamics likely cause the reported changes in the speed and amplitude of kinetochore oscillations following depletion of KIF18A, and the resulting severe chromosome congression defect 106,114,115 .…”

Spatial Control of Microtubule Length and Lifetime by Opposing Stabilizing and Destabilizing Functions of Kinesin-8

“…Kinesin-8 is required for metaphase congression in Drosophila S2 and human HeLa cells [40, 41]. Moreover, the human kinesin-8, Kif18A, accumulates as a gradient on kinetochore MTs [41], stabilizes dynamic MTs in vitro [15, 16], and has a nucleotide-dependent MT destabilizing activity [7, 42]. Thus, the spatial regulation of MTs by kinesin-8 may be a conserved mechanism to differentially control the length or lifetime of cellular MTs.…”

The structure of apo-kinesin bound to tubulin links the nucleotide cycle to movement

“…In addition, kinesin motor domains in all their nucleotide states, bound to microtubules, have been studied by cryo-electron microscopy (EM) at resolutions up to ca. 9 Å [12][13][14][15] . However, for a complete description of the kinesin nucleotide cycle, a high-resolution structure of the nucleotide-free kinesin bound to its track protein (nucleotide-free complex) is required.…”