Microtubule capture by mitotic kinesin centromere protein E (CENP-E).

Centromere protein E, CENP-E, is a kinetochore-associated kinesin-7 that establishes the microtubule-chromosome linkage and transports monooriented chromosomes to the spindle equator along kinetochore fibers of already bioriented chromosomes. As a processive kinesin, CENP-E uses a hand-over-hand mechanism, yet a number of studies suggest that CENP-E exhibits mechanistic differences from other processive kinesins that may be important for its role in chromosome congression. The results reported here show that association of CENP-E with the microtubule is unusually slow at 0.08 μM(-1) s(-1) followed by slow ADP release at 0.9 s(-1). ATP binding and hydrolysis are fast with motor dissociation from the microtubule at 1.4 s(-1), suggesting that CENP-E head detachment from the microtubule, possibly controlled by phosphate release, determines the rate of stepping during a processive run because the rate of microtubule gliding corresponds to 1.4 steps/s. We hypothesize that the unusually slow CENP-E microtubule association step favors CENP-E binding of stable microtubules over dynamic ones, a mechanism that would bias CENP-E binding to kinetochore fibers.