Protein Friction Limits Diffusive and Directed Movements of Kinesin Motors on Microtubules
Protein Friction Limits Diffusive and Directed Movements of Kinesin Motors on Microtubules
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DOI：
10.1126/science.1174923
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发表时间：
2009-08-14
期刊：
影响因子：
56.9
通讯作者：
Schaeffer, Erik
中科院分区：
文献类型：
--
作者：
Bormuth, Volker;Varga, Vladimir;Schaeffer, Erik
摩擦限制了宏观发动机的运行，对微观机械装置的性能至关重要。我们报告了生物纳米机器中摩擦的测量。使用光学镊子，我们表征了单个kinesin-8马达蛋白与其微管轨道相互作用的摩擦阻力。在低速和无能量时，摩擦阻力与扩散系数的关系符合爱因斯坦关系。在较高的速度下，摩擦阻力呈非线性增加，与马达沿微管在相邻的微管蛋白二聚体之间跳跃8纳米一致，且不对称，反映了微管的结构极性。我们认为，这些摩擦力来自于马达结构域和微管之间的断裂，它们限制了运动蛋白的速度和效率。
Friction limits the operation of macroscopic engines and is critical to the performance of micromechanical devices. We report measurements of friction in a biological nanomachine. Using optical tweezers, we characterized the frictional drag force of individual kinesin-8 motor proteins interacting with their microtubule tracks. At low speeds and with no energy source, the frictional drag was related to the diffusion coefficient by the Einstein relation. At higher speeds, the frictional drag force increased nonlinearly, consistent with the motor jumping 8 nanometers between adjacent tubulin dimers along the microtubule, and was asymmetric, reflecting the structural polarity of the microtubule. We argue that these frictional forces arise from breaking bonds between the motor domains and the microtubule, and they limit the speed and efficiency of kinesin.