Sindelar Charles V
Department of Molecular Biophysics and Biochemistry, Yale University, SHMC-E25, 333 Cedar Street, New Haven, CT 06520-8024 USA.
Biophys Rev. 2011 Jun;3(2):85-100. doi: 10.1007/s12551-011-0049-4. Epub 2011 Jun 4.
Recent structural observations of kinesin-1, the founding member of the kinesin group of motor proteins, have led to substantial gains in our understanding of this molecular machine. Kinesin-1, similar to many kinesin family members, assembles to form homodimers that use alternating ATPase cycles of the catalytic motor domains, or "heads", to proceed unidirectionally along its partner filament (the microtubule) via a hand-over-hand mechanism. Cryo-electron microscopy has now revealed 8-Å resolution, 3D reconstructions of kinesin-1•microtubule complexes for all three of this motor's principal nucleotide-state intermediates (ADP-bound, no-nucleotide, and ATP analog), the first time filament co-complexes of any cytoskeletal motor have been visualized at this level of detail. These reconstructions comprehensively describe nucleotide-dependent changes in a monomeric head domain at the secondary structure level, and this information has been combined with atomic-resolution crystallography data to synthesize an atomic-level "seesaw" mechanism describing how microtubules activate kinesin's ATP-sensing machinery. The new structural information revises or replaces key details of earlier models of kinesin's ATPase cycle that were based principally on crystal structures of free kinesin, and demonstrates that high-resolution characterization of the kinesin-microtubule complex is essential for understanding the structural basis of the cycle. I discuss the broader implications of the seesaw mechanism within the cycle of a fully functional kinesin dimer and show how the seesaw can account for two types of "gating" that keep the ATPase cycles of the two heads out of sync during processive movement.
驱动蛋白-1是驱动蛋白家族中最早被发现的成员，近期对其结构的研究使我们对这一分子机器有了更深入的了解。与许多驱动蛋白家族成员一样，驱动蛋白-1组装形成同型二聚体，利用催化运动结构域（即“头部”）交替进行的ATP酶循环，通过手拉手机制沿着其伙伴细丝（微管）单向移动。冷冻电子显微镜现已揭示了这种驱动蛋白三种主要核苷酸状态中间体（ADP结合态、无核苷酸态和ATP类似物态）与微管复合物的8埃分辨率三维重建结构，这是首次在如此高的细节水平上观察到任何细胞骨架驱动蛋白的细丝共复合物。这些重建结构全面描述了单体头部结构域在二级结构水平上依赖核苷酸的变化，并且该信息已与原子分辨率晶体学数据相结合，以合成一种原子水平的“跷跷板”机制，描述微管如何激活驱动蛋白的ATP传感机制。新的结构信息修正或取代了早期主要基于游离驱动蛋白晶体结构的驱动蛋白ATP酶循环模型的关键细节，并表明对驱动蛋白-微管复合物进行高分辨率表征对于理解该循环的结构基础至关重要。我将讨论跷跷板机制在功能完备的驱动蛋白二聚体循环中的更广泛意义，并展示跷跷板机制如何解释两种“门控”类型，即在持续运动过程中使两个头部的ATP酶循环不同步。
