Nara Ikuko, Ishiwata Shin'ichi
Department of Physics, School of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo169-8555, Japan.
Department of Physics, School of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo169-8555, Japan; Advanced Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo169-8555, Japan.
Biophysics (Nagoya-shi). 2006 Feb 22;2:13-21. doi: 10.2142/biophysics.2.13. eCollection 2006.
Kinesin is a motor protein that processively moves step by step along a microtubule. To investigate the effects of temperature on run length, i.e., processivity of kinesin motility, we performed a single-molecular bead assay at temperature range of 20-40°C. An increase in the walking velocity of kinesin corresponded to the Arrhenius activation enthalpy of 48 kJ/mol, being consistent with the previous reports. Here, we found that the run length increased, that is, the kinesin processivity enhanced with increasing temperature. Then, we estimated the probability of detachment of kinesin from a microtubule per one 8-nm stepping event, and found that it diminishes from 0.014 to 0.006/step with increasing temperature from 20 to 40°C. And we noticed that prolonged incubation at 30, 35 and 40°C significantly slowed down the walking velocity, but further increased the run length and duration. Those results are interpreted according to the effect of temperature on the rate constants of some key kinetic steps in the ATPase cycle.
驱动蛋白是一种能沿着微管逐步进行性移动的马达蛋白。为了研究温度对行程长度的影响，即驱动蛋白运动的持续性，我们在20 - 40°C的温度范围内进行了单分子磁珠实验。驱动蛋白行走速度的增加对应着48 kJ/mol的阿仑尼乌斯活化焓，这与之前的报道一致。在此，我们发现行程长度增加，也就是说，驱动蛋白的持续性随着温度升高而增强。然后，我们估计了每一次8纳米步移事件中驱动蛋白从微管上脱离的概率，发现随着温度从20°C升高到40°C，该概率从0.014降至0.006/步。并且我们注意到在30°C、35°C和40°C下长时间孵育会显著减慢行走速度，但会进一步增加行程长度和持续时间。这些结果是根据温度对ATP酶循环中一些关键动力学步骤速率常数的影响来解释的。
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