THE FORCE EXERTED BY A SINGLE KINESIN MOLECULE AGAINST A VISCOUS LOAD
THE FORCE EXERTED BY A SINGLE KINESIN MOLECULE AGAINST A VISCOUS LOAD
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DOI：
10.1016/s0006-3495(94)80537-5
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发表时间：
1994-08-01
影响因子：
3.4
通讯作者：
HOWARD, J
中科院分区：
文献类型：
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作者：
HUNT, AJ;GITTES, F;HOWARD, J
动蛋白是一种马达蛋白，它利用三磷酸腺苷水解产生的能量来推动细胞器沿微管的运输。为了探索这种化学-机械-机械能传递反应的机理，通过增加缓冲溶液的粘度来干扰微管在涂有动蛋白的玻璃表面的运动。当低密度流动分析中使用的溶液的粘度通过添加多糖和多肽增加约100倍时，承受来自流体的较大阻力的较长的微管移动得比较短的微管慢。微管的运动速度与电机的阻力成线性关系。在最低的动蛋白密度下，稀释实验表明运动是由单个动蛋白分子引起的，对线性关系的外推得出每个马达的最大时间平均阻力为4.2+/-0.5pN(平均+/-实验SE)。力的大小与一种类型的‘棘轮’模型相反，在该模型中，假设电机是为了纠正微管的扩散；在高粘度时，扩散太慢，无法解释观察到的速度。另一方面，我们的数据与力是电机内弹性元件应变的结果的模型是一致的；这些模型包括不同的“棘轮”模型(由A.F.赫胥黎在1957年提出的类型)以及“功率-冲程”模型。
Kinesin is a motor protein that uses the energy derived from the hydrolysis of ATP to power the transport of organelles along microtubules. To probe the mechanism of this chemical-ta-mechanical energy transduction reaction, the movement of microtubules across glass surfaces coated with kinesin was perturbed by raising the viscosity of the buffer solution. When the viscosity of the solution used in the low density motility assay was increased approximately 100-fold through addition of polysaccharides and polypeptides, the longer microtubules, which experienced a larger drag force from the fluid, moved more slowly than the shorter ones. The speed of movement of a microtubule depended linearly on the drag force loading the motor. At the lowest kinesin density, where dilution experiments indicated that the movement was caused by a single kinesin molecule, extrapolation of the linear relationship yielded a maximum time-averaged drag force of 4.2 +/- 0.5 pN per motor (mean +/- experimental SE). The magnitude of the force argues against one type of ''ratchet' model in which the motor is hypothesized to rectify the diffusion of the microtubule; at high viscosity, diffusion is too slow to account for the observed speeds. On the other hand, our data are consistent with models in which force is a consequence of strain developed in an elastic element within the motor; these models include a different ''ratchet' model (of the type proposed by A. F. Huxley in 1957) as well as ''power-stroke'' models.