The cytoskeleton forms a dynamic network that generates fluctuations larger than thermal agitation of the cytoplasm¹. Here, we tested whether dynein, a minus-end-directed microtubule (MT) motor², can harness energy from these fluctuations using optical trapping in vitro. We show that dynein forms an asymmetric slip bond with MTs, where its detachment rate increases more slowly under hindering forces than assisting forces. This asymmetry enables dynein to generate unidirectional motility towards the minus-end from force fluctuations. Consistent with our model, oscillatory forces exerted by the trap drive dynein stepping without net force and ATP. Dynein is capable of ratcheting towards the minus-end, even when the net force is in the plus-end direction. With ATP, force oscillations increase the velocity and stall force of dynein as it transports cargos and glides MTs. Therefore, dynein is a mechanical ratchet that rectifies cytoskeletal fluctuations to move faster and resists higher forces along MTs.

细胞骨架形成动态网络，其产生的波动大于细胞质¹的热搅动。在这里，我们测试了动力蛋白是否是负端定向微管 (MT) 电机²，可以利用体外光捕获从这些波动中获取能量。我们表明，动力蛋白与 MTs 形成不对称的滑移键，其分离率在阻碍力下比辅助力下增加得更慢。这种不对称性使动力蛋白能够从力波动产生朝向负端的单向运动。与我们的模型一致，陷阱施加的振荡力驱动动力蛋白在没有净力和 ATP 的情况下步进。动力蛋白能够向负端棘轮，即使净力在正端方向。使用 ATP，力振荡会增加动力蛋白在运输货物和滑行 MT 时的速度和失速力。因此，动力蛋白是一种机械棘轮，可纠正细胞骨架波动以更快地移动并抵抗沿 MT 的更高力。