Cytoskeletal motors drive many essential cellular processes. For example, kinesin-1 transports cargo in a step-wise manner along microtubules. To resolve rotations during stepping, we used optical tweezers combined with an optical microprotractor and torsion balance using highly birefringent microspheres to directly and simultaneously measure the translocation, rotation, force, and torque generated by individual kinesin-1 motors. While, at low adenosine 5′-triphosphate (ATP) concentrations, motors did not generate torque, we found that motors translocating along microtubules at saturating ATP concentrations rotated unidirectionally, producing significant torque on the probes. Accounting for the rotational work makes kinesin a highly efficient machine. These results imply that the motor’s gait follows a rotary hand-over-hand mechanism. Our method is generally applicable to study rotational and linear motion of molecular machines, and our findings have implications for kinesin-driven cellular processes.

中文翻译：

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驱动蛋白单向旋转并在微管上行走时产生扭矩

细胞骨架马达驱动许多重要的细胞过程。例如，kinesin-1 沿着微管逐步运输货物。为了解决步进过程中的旋转问题，我们使用光学镊子与光学微量角器和使用高双折射微球的扭力天平相结合，直接并同时测量单个 kinesin-1 电机产生的易位、旋转、力和扭矩。虽然在低腺苷 5'-三磷酸 (ATP) 浓度下，电机不会产生扭矩，但我们发现在饱和 ATP 浓度下沿微管易位的电机单向旋转，在探针上产生显着扭矩。考虑到旋转功使驱动蛋白成为高效机器。这些结果意味着电机的步态遵循旋转的手-手机制。