Yajima Junichiro, Cross Robert A
Molecular Motors Group, Marie Curie Research Institute, The Chart, Oxted, Surrey RH8 0TL, UK.
Nat Chem Biol. 2005 Nov;1(6):338-41. doi: 10.1038/nchembio740. Epub 2005 Oct 9.
Kinesin-1 is a twin-headed molecular motor that moves along microtubules in 8-nm steps, using a walking action in which the two heads interact alternately with the microtubule. Constructs with only one head can also produce impulses of force and motion, indicating that the walking action is an amplification strategy that leverages an underlying force-generating event. Recent work suggests that directional force is produced either by directionally biased selection of microtubule binding sites or by a conformational change subsequent to the binding event. We report here that surface-attached rat kinesin-1 monomers drive counterclockwise rotation of sliding microtubules around their axes, and that by manipulating the assay geometry, we could reduce or block the torsional motion with negligible effects on the axial motion. We can account for this behavior on the simple assumption that kinesin heads tend to bind to the closest available tubulin heterodimer in the lattice, but only in the case where an additional biasing process is present that shifts the start position for diffusion-to-capture toward the microtubule plus end by approximately 1 nm.
驱动蛋白-1是一种双头分子马达，它以8纳米的步长沿着微管移动，通过一种行走动作，其中两个头部交替与微管相互作用。只有一个头部的构建体也能产生力和运动的脉冲，这表明行走动作是一种利用潜在力产生事件的放大策略。最近的研究表明，定向力要么是由微管结合位点的定向偏向选择产生的，要么是由结合事件后的构象变化产生的。我们在此报告，表面附着的大鼠驱动蛋白-1单体驱动滑动微管绕其轴逆时针旋转，并且通过操纵检测几何结构，我们可以减少或阻止扭转运动，而对轴向运动的影响可以忽略不计。我们可以基于这样一个简单的假设来解释这种行为，即驱动蛋白头部倾向于与晶格中最接近的可用微管蛋白异二聚体结合，但只有在存在额外的偏向过程的情况下，该过程会使扩散到捕获的起始位置向微管正端移动约1纳米。
