Ray S, Meyhöfer E, Milligan R A, Howard J
Department of Physiology and Biophysics, University of Washington, Seattle 98195.
J Cell Biol. 1993 Jun;121(5):1083-93. doi: 10.1083/jcb.121.5.1083.
We tested the hypothesis that kinesin moves parallel to the microtubule's protofilament axis. We polymerized microtubules with protofilaments that ran either parallel to the microtubule's long axis or that ran along shallow helical paths around the cylindrical surface of the microtubule. When gliding across a kinesin-coated surface, the former microtubules did not rotate. The latter microtubules, those with supertwisted protofilaments, did rotate; the pitch and handedness of the rotation accorded with the supertwist measured by electron cryo-microscopy. The results show that kinesin follows a path parallel to the protofilaments with high fidelity. This implies that the distance between consecutive kinesin-binding sites along the microtubule must be an integral multiple of 4.1 nm, the tubulin monomer spacing along the protofilament, or a multiple of 8.2 nm, the dimer spacing.
我们验证了驱动蛋白沿着微管原纤维轴平行移动的假说。我们聚合了原纤维与微管长轴平行或沿着微管圆柱表面浅螺旋路径排列的微管。当在涂有驱动蛋白的表面滑行时，前一种微管不会旋转。后一种微管，即原纤维具有超螺旋的微管，会发生旋转；旋转的螺距和方向与通过电子冷冻显微镜测量的超螺旋一致。结果表明，驱动蛋白以高保真度沿着与原纤维平行的路径移动。这意味着沿着微管连续的驱动蛋白结合位点之间的距离必须是4.1纳米（沿原纤维的微管蛋白单体间距）的整数倍，或者是8.2纳米（二聚体间距）的倍数。
