Cellular Nanoscience, Center for Plant Molecular Biology, University of Tübingen, 72076 Tübingen, Germany.
Cellular Nanoscience, Center for Plant Molecular Biology, University of Tübingen, 72076 Tübingen, Germany
Proc Natl Acad Sci U S A. 2017 Oct 10;114(41):10894-10899. doi: 10.1073/pnas.1706985114. Epub 2017 Sep 25.
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.
细胞骨架马达驱动许多重要的细胞过程。例如，驱动蛋白-1 沿着微管以逐步的方式运输货物。为了解决在步进过程中的旋转，我们使用光学镊子结合光学微角度计和扭转天平，使用高度双折射微球，直接且同时测量单个驱动蛋白-1 马达产生的转位、旋转、力和扭矩。虽然在低腺苷 5'-三磷酸 (ATP) 浓度下，马达不会产生扭矩，但我们发现，在饱和 ATP 浓度下沿微管转运的马达单向旋转，对探针产生显著的扭矩。考虑到旋转功，驱动蛋白成为一种高效的机器。这些结果表明，马达的步态遵循旋转的手对手机制。我们的方法通常适用于研究分子机器的旋转和线性运动，我们的发现对驱动蛋白驱动的细胞过程具有重要意义。
