Effects of stalk orientation and size of trapped bead on force–velocity relation of kinesin motor determined using single molecule optical trapping methods
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引用次数: 0
Abstract
Conventional kinesin protein is a prototypical biological molecular motor that can step processively on microtubules towards the plus end by hydrolyzing ATP molecules, performing the biological function of intracellular transports. An important characteristic of the kinesin is the load dependence of its velocity, which is usually measured by using the single molecule optical trapping method with a large-sized bead attached to the motor stalk. Puzzlingly, even for the same kinesin, some experiments showed that the velocity is nearly independent of the forward load whereas others showed that the velocity decreases evidently with the increase in the magnitude of the forward load. Here, a theoretical explanation is provided of why different experiments give different dependencies of the velocity on the forward load. It is shown that both the stalk orientation and bead size play a critical role in the different dependencies. Additionally, the reason why the optical trapping experiments with the movable trap usually gave a sigmoid form of the velocity versus backward load whereas with the fixed trap gave a nearly linear form is also explained theoretically. The study is not only critical to the understanding of the response of the motor to the load but also provides strong insights into the coupling mechanism of the motor.
传统的驱动蛋白是一种典型的生物分子马达,它可以通过水解 ATP 分子在微管上向正端移动,发挥细胞内运输的生物功能。驱动蛋白的一个重要特征是其速度与负载有关,通常使用单分子光学捕获法测量其速度,在马达柄上连接一个大尺寸的珠子。令人费解的是,即使是同样的驱动蛋白,有些实验表明其速度几乎与前向载荷无关,而有些实验则表明其速度随着前向载荷的增加而明显下降。在此,我们从理论上解释了为什么不同的实验得出的速度与前向载荷的关系不同。实验结果表明,在不同的依赖关系中,柄的方向和珠子的大小都起着至关重要的作用。此外,还从理论上解释了为什么使用可移动捕集器进行的光学捕集实验通常给出速度与后向载荷的曲线,而使用固定捕集器则给出近似线性的曲线。这项研究不仅对理解电机对负载的响应至关重要,而且对电机的耦合机制提供了深刻的见解。
期刊介绍:
Many physicists are turning their attention to domains that were not traditionally part of physics and are applying the sophisticated tools of theoretical, computational and experimental physics to investigate biological processes, systems and materials.
The Journal of Biological Physics provides a medium where this growing community of scientists can publish its results and discuss its aims and methods. It welcomes papers which use the tools of physics in an innovative way to study biological problems, as well as research aimed at providing a better understanding of the physical principles underlying biological processes.