Fehr Adrian N, Asbury Charles L, Block Steven M
Biophys J. 2008 Feb 1;94(3):L20-2. doi: 10.1529/biophysj.107.126839. Epub 2007 Dec 14.
Kinesin is a two-headed motor protein that transports cargo inside cells by moving stepwise on microtubules. Its exact trajectory along the microtubule is unknown: alternative pathway models predict either uniform 8-nm steps or alternating 7- and 9-nm steps. By analyzing single-molecule stepping traces from "limping" kinesin molecules, we were able to distinguish alternate fast- and slow-phase steps and thereby to calculate the step sizes associated with the motions of each of the two heads. We also compiled step distances from nonlimping kinesin molecules and compared these distributions against models predicting uniform or alternating step sizes. In both cases, we find that kinesin takes uniform 8-nm steps, a result that strongly constrains the allowed models.
驱动蛋白是一种双头马达蛋白，通过在微管上逐步移动来运输细胞内的货物。其沿微管的确切轨迹尚不清楚：替代途径模型预测要么是均匀的8纳米步长，要么是交替的7纳米和9纳米步长。通过分析“跛行”驱动蛋白分子的单分子步进轨迹，我们能够区分交替的快相和慢相步骤，从而计算与两个头部各自运动相关的步长。我们还汇总了非跛行驱动蛋白分子的步距，并将这些分布与预测均匀或交替步长的模型进行比较。在这两种情况下，我们发现驱动蛋白采取均匀的8纳米步长，这一结果强烈限制了允许的模型。
