Case R B, Pierce D W, Hom-Booher N, Hart C L, Vale R D
Department of Pharmacology, University of California, San Francisco 94143, USA.
Cell. 1997 Sep 5;90(5):959-66. doi: 10.1016/s0092-8674(00)80360-8.
Members of the kinesin superfamily share a similar motor catalytic domain yet move either toward the plus end (e.g., conventional kinesin) or the minus end (e.g., Ncd) of microtubules. The structural features that determine the polarity of movement have remained enigmatic. Here, we show that kinesin's catalytic domain (316 residues) in a dimeric construct (560 residues) can be replaced with the catalytic domain of Ncd and that the resultant motor moves in the kinesin direction. We also demonstrate that this chimera does not move processively over many tubulin subunits, which is similar to Ncd but differs from the highly processive motion of conventional kinesin. These findings reveal that the catalytic domain contributes to motor processivity but does not control the polarity of movement. We propose that a region adjacent to the catalytic domain serves as a mechanical transducer that determines directionality.
驱动蛋白超家族的成员共享一个相似的马达催化结构域，但它们要么朝着微管的正端移动（例如，传统驱动蛋白），要么朝着微管的负端移动（例如，Ncd）。决定运动极性的结构特征一直是个谜。在这里，我们表明，在一个二聚体结构（560个残基）中，驱动蛋白的催化结构域（316个残基）可以被Ncd的催化结构域取代，并且由此产生的马达朝着驱动蛋白的方向移动。我们还证明，这种嵌合体不会在许多微管蛋白亚基上持续移动，这与Ncd相似，但与传统驱动蛋白的高度持续运动不同。这些发现表明，催化结构域有助于马达的持续运动，但并不控制运动的极性。我们提出，与催化结构域相邻的一个区域作为一个机械换能器，决定了方向性。
