Yildiz Ahmet, Tomishige Michio, Gennerich Arne, Vale Ronald D
Department of Cellular and Molecular Pharmacology and the Howard Hughes Medical Institute, University of California, San Francisco, CA 94158, USA.
Cell. 2008 Sep 19;134(6):1030-41. doi: 10.1016/j.cell.2008.07.018.
Kinesin advances 8 nm along a microtubule per ATP hydrolyzed, but the mechanism responsible for coordinating the enzymatic cycles of kinesin's two identical motor domains remains unresolved. Here, we have tested whether such coordination is mediated by intramolecular tension generated by the "neck linkers," mechanical elements that span between the motor domains. When tension is reduced by extending the neck linkers with artificial peptides, the coupling between ATP hydrolysis and forward stepping is impaired and motor's velocity decreases as a consequence. However, speed recovers to nearly normal levels when external tension is applied by an optical trap. Remarkably, external load also induces bidirectional stepping of an immotile kinesin that lacks its mechanical element (neck linker) and fuel (ATP). Our results indicate that the kinesin motor domain senses and responds to strain in a manner that facilitates its plus-end-directed stepping and communication between its two motor domains.
驱动蛋白每水解一个三磷酸腺苷（ATP）会沿着微管前进8纳米，但负责协调驱动蛋白两个相同运动结构域酶促循环的机制仍未得到解决。在这里，我们测试了这种协调是否由“颈部连接体”产生的分子内张力介导，颈部连接体是跨越运动结构域的机械元件。当通过人工肽段延长颈部连接体来降低张力时，ATP水解与向前步进之间的耦合受到损害，结果驱动蛋白的速度降低。然而，当通过光镊施加外部张力时，速度恢复到几乎正常的水平。值得注意的是，外部负载还会诱导缺乏机械元件（颈部连接体）和燃料（ATP）的静止驱动蛋白进行双向步进。我们的结果表明，驱动蛋白运动结构域以一种促进其向正端步进以及两个运动结构域之间通讯的方式感知并响应应变。
