Department of Biology and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
J Biol Chem. 2012 Jul 20;287(30):24894-904. doi: 10.1074/jbc.M112.376830. Epub 2012 May 27.
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.
着丝粒蛋白 E（CENP-E）是一种与动粒相关的驱动蛋白-7，它建立微管-染色体连接，并沿已双定向染色体的动粒纤维将单定向染色体运送到纺锤体赤道。作为一种成束运动的驱动蛋白，CENP-E 使用交替机制，但许多研究表明，CENP-E 表现出与其他成束运动的驱动蛋白不同的机械特性，这对于其在染色体汇聚中的作用可能很重要。这里报道的结果表明，CENP-E 与微管的结合速度非常缓慢，为 0.08 μM(-1) s(-1)，随后 ADP 以 0.9 s(-1)的速度缓慢释放。ATP 结合和水解速度很快，马达与微管解离速度为 1.4 s(-1)，这表明 CENP-E 头部与微管的脱离（可能由磷酸盐释放控制）决定了在成束运动过程中的步速，因为微管滑行的速度对应于 1.4 步/s。我们假设 CENP-E 与微管的结合速度非常缓慢，有利于 CENP-E 结合稳定的微管而不是动态的微管，这种机制会使 CENP-E 偏向于与动粒纤维结合。
