Hirose K, Amos L A
National Institute for Advanced Interdisciplinary Research, Tsukuba, Ibaraki, Japan.
Cell Mol Life Sci. 1999 Oct 15;56(3-4):184-99. doi: 10.1007/s000180050421.
Images, calculated from electron micrographs, show the three-dimensional structures of microtubules and tubulin sheets decorated stoichiometrically with motor protein molecules. Dimeric motor domains (heads) of kinesin and ncd, the kinesin-related protein that moves in the reverse direction, each appeared to bind to tubulin in the same way, by one of their two heads. The second heads show an interesting difference in position that seems to be related to the directions of movement of the two motors. X-ray crystallographic results showing the structures of kinesin and ncd to be very similar at atomic resolution, and homologous also to myosin, suggest that the two motor families may use mechanisms that have much in common. Nevertheless, myosins and kinesins differ kinetically. Also, whereas conformational changes in the myosin catalytic domain are amplified by a long lever arm that connects it to the stalk domain, kinesin and ncd do not appear to possess a structure with a similar function but may rely on biased diffusion in order to move along microtubules.
由电子显微照片计算得出的图像显示了微管和微管蛋白片层的三维结构，这些结构被运动蛋白分子以化学计量方式修饰。驱动蛋白和ncd（一种反向移动的驱动蛋白相关蛋白）的二聚体运动结构域（头部），似乎各自通过其两个头部之一以相同方式与微管蛋白结合。第二个头部在位置上显示出有趣的差异，这似乎与两种马达的运动方向有关。X射线晶体学结果表明，驱动蛋白和ncd在原子分辨率下结构非常相似，并且与肌球蛋白也同源，这表明这两个运动蛋白家族可能使用有许多共同之处的机制。然而，肌球蛋白和驱动蛋白在动力学上有所不同。此外，肌球蛋白催化结构域中的构象变化通过连接它与柄部结构域的长杠杆臂放大，而驱动蛋白和ncd似乎不具备具有类似功能的结构，而是可能依赖于偏向扩散来沿着微管移动。
