Processivity of the motor protein kinesin requires two heads.
Processivity of the motor protein kinesin requires two heads.
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DOI：
10.1083/jcb.140.6.1395
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发表时间：
1998-03-23
期刊：
影响因子：
--
通讯作者：
Howard J
中科院分区：
文献类型：
--
作者：
Hancock WO;Howard J
一个驱动蛋白分子可以沿着微管移动数百步而不会解离。解释这种过程运动的一种假设是，驱动蛋白的两个头部的结合是协调的，因此至少有一个头部总是与微管结合。为了验证这一假设，在体外微管滑动实验中检测了全长单头动力蛋白异二聚体的运动性。当单头驱动蛋白的表面密度降低时，微管在表面上着陆和移动的速度以及微管移动的距离都急剧下降，这表明单个单头驱动蛋白马达不是进步性的，大约4到6个单头驱动蛋白分子是必要的，足以连续移动一个微管。在高ATP浓度下，单个单头驱动蛋白分子非常缓慢地从微管中分离出来（速率低于每秒一个），比双头运动时的分离速度慢100倍。这种缓慢的分离直接支持一种协调的、手拉手的模型，其中二聚体中一个头的快速分离取决于第二个头的结合。
A single kinesin molecule can move for hundreds of steps along a microtubule without dissociating. One hypothesis to account for this processive movement is that the binding of kinesin's two heads is coordinated so that at least one head is always bound to the microtubule. To test this hypothesis, the motility of a full-length single-headed kinesin heterodimer was examined in the in vitro microtubule gliding assay. As the surface density of single-headed kinesin was lowered, there was a steep fall both in the rate at which microtubules landed and moved over the surface, and in the distance that microtubules moved, indicating that individual single-headed kinesin motors are not processive and that some four to six single-headed kinesin molecules are necessary and sufficient to move a microtubule continuously. At high ATP concentration, individual single-headed kinesin molecules detached from microtubules very slowly (at a rate less than one per second), 100-fold slower than the detachment during two-headed motility. This slow detachment directly supports a coordinated, hand-over-hand model in which the rapid detachment of one head in the dimer is contingent on the binding of the second head.