Minus-end-directed motor ncd exhibits processive movement that is enhanced by microtubule bundling in vitro
Minus-end-directed motor ncd exhibits processive movement that is enhanced by microtubule bundling in vitro
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DOI：
10.1016/j.cub.2007.12.056
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发表时间：
2008-01-22
期刊：
影响因子：
9.2
通讯作者：
Toyoshima, Yoko Yano
中科院分区：
文献类型：
--
作者：
Furuta, Ken'ya;Toyoshima, Yoko Yano
果蝇Ncd是驱动蛋白-14A家族成员，对减数分裂和有丝分裂至关重要[1 - 7]。Ncd是一种负末端定向的马达蛋白，在尾部区域具有ATP非依赖性微管结合位点，这使其能够作为微管的动态交联剂来组装和维持纺锤体[8 - 12]。虽然无尾Ncd已被证明是非进行性的[13 - 16]，但Ncd尾在单分子运动中的作用尚不清楚。在这里，我们表明，个别NCD二聚体包含的尾部区域可以移动processively沿着微管在非常低的离子强度，这提供了第一个证据的持续性为负端导向驱动蛋白。GFP-Ncd的运动由单向运动和扩散运动两部分组成，对离子强度敏感。运动性的截断系列的Ncd和微管蛋白尾部的去除表明，Ncd尾部作为一个静电系绳微管，在较高的离子条件下，Ncd显示只有一个小的偏差扩散沿着"单一"的微管，而它表现出进行性运动沿着"捆绑"的微管。这种特性可能允许Ncd优先在聚焦的微管附近积累，然后交联和滑动微管，可能有助于动态纺锤体自组织。
Drosophila Ncd, a kinesin-14A family member, is essential for meiosis and mitosis [1 - 7]. Ncd is a minus-end-directed motor protein that has an ATP-independent microtubule binding site in the tail region, which enables it to act as a dynamic crosslinker of microtubules to assemble and maintain the spindle [8 - 12]. Although a tailless Ncd has been shown to be nonprocessive [13 - 16], the role of the Ncd tail in single-molecule motility is unknown. Here, we show that individual Ncd dimers containing the tail region can move processively along microtubules at very low ionic strength, which provides the first evidence of processivity for minus-end-directed kinesins. The movement of GFP-Ncd consists of both a unidirectional and a diffusive element, and it was sensitive to ionic strength. Motility of a truncation series of Ncd and removal of the tubulin tail suggested that the Ncd tail serves as an electrostatic tether to microtubules, Under higher ionic conditions, Ncd showed only a small bias in diffusion along '' single '' microtubules, whereas it exhibited processive movement along '' bundled '' microtubules. This property may allow Ncd to accumulate preferentially in the vicinity of focused microtubules and then to crosslink and slide microtubules, possibly contributing to dynamic spindle self-organization.