Soft Biosystem Group, Laboratories for Nanobiology, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan.
Nat Commun. 2012 Jul 17;3:956. doi: 10.1038/ncomms1934.
Motor proteins are force-generating nanomachines that are highly adaptable to their ever-changing biological environments and have a high energy conversion efficiency. Here we constructed an imaging system that uses optical tweezers and a DNA handle to visualize elementary mechanical processes of a nanomachine under load. We apply our system to myosin-V, a well-known motor protein that takes 72 nm 'hand-over-hand' steps composed of a 'lever-arm swing' and a 'brownian search-and-catch'. We find that the lever-arm swing generates a large proportion of the force at low load (<0.5 pN), resulting in 3 k(B)T of work. At high load (1.9 pN), however, the contribution of the brownian search-and-catch increases to dominate, reaching 13 k(B)T of work. We believe the ability to switch between these two force-generation modes facilitates myosin-V function at high efficiency while operating in a dynamic intracellular environment.
马达蛋白是产生力的纳米机器，它们高度适应不断变化的生物环境，并且具有高效率的能量转换能力。在这里，我们构建了一个使用光学镊子和 DNA 手柄的成像系统，以可视化纳米机器在负载下的基本机械过程。我们将我们的系统应用于肌球蛋白-V，这是一种众所周知的马达蛋白，它采取 72nm 的“手拉手”步骤，由“臂摆动”和“布朗搜索和捕捉”组成。我们发现臂摆动在低负载（<0.5pN）下产生了很大一部分力，导致 3k(B)T 的功。然而，在高负载（1.9pN）下，布朗搜索和捕捉的贡献增加，占据主导地位，达到 13k(B)T 的功。我们相信，这种在两种力产生模式之间切换的能力，使得肌球蛋白-V 在高效运行的同时，能够在动态的细胞内环境中发挥作用。
