In in vitro microtubule gliding assays, most kinesins drive the rotation of gliding microtubules around their longitudinal axes in a corkscrew motion. The corkscrewing pitch is smaller than the supertwisted protofilament pitch of microtubules, indicating that the corkscrewing pitch is an inherent property of kinesins. To elucidate the molecular mechanisms through which kinesins corkscrew the microtubule, we performed three‐dimensional tracking of a quantum dot bound to a microtubule translocating over a surface coated with single‐headed kinesin‐1 s under various assay conditions to alter the interactions between the kinesin and microtubule. Although alternations in kinesin concentration, ionic strength, and ATP concentration changed both gliding and rotational velocities, the corkscrewing pitch remained left‐handed and constant at ~0.3 μm under all tested conditions apart from a slight increase in pitch at a low ATP concentration. We then used our system to analyze the effect of point mutations in the N‐terminal β‐strand protruding from the kinesin motor core and found mutations that decreased the corkscrewing pitch. Our findings confirmed that the corkscrewing motion of microtubules is caused by the intrinsic properties of the kinesin and demonstrates that changes in the active or retarding force originating from the N‐terminal β‐strand in the head modulate the pitch.

中文翻译：

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单头驱动蛋白 1 的 N 端 β 链可以调节离轴力的产生和由此产生的旋转螺距。

在体外微管滑动试验中，大多数驱动蛋白驱动滑动微管绕其纵轴以螺旋式运动旋转。螺旋螺距小于微管的超扭曲原丝节距，表明螺旋螺距是驱动蛋白的固有特性。为了阐明驱动蛋白螺旋状微管的分子机制，我们对绑定到微管上的量子点进行了三维跟踪，该微管在各种测定条件下在涂有单头驱动蛋白-1s 的表面上易位，以改变驱动蛋白之间的相互作用和微管。尽管驱动蛋白浓度、离子强度和 ATP 浓度的变化改变了滑动速度和旋转速度，但螺旋螺距保持左旋且恒定在~0。除了在低 ATP 浓度下间距略有增加外，在所有测试条件下均为 3 μm。然后，我们使用我们的系统分析了从驱动蛋白运动核心突出的 N 端 β 链中点突变的影响，并发现了降低开瓶器螺距的突变。我们的研究结果证实，微管的螺旋运动是由驱动蛋白的内在特性引起的，并表明源自头部 N 端 β 链的主动或阻滞力的变化会调节音高。