Ueno Hironori, Bui Khanh Huy, Ishikawa Takuji, Imai Yohsuke, Yamaguchi Takami, Ishikawa Takashi
Institute of Molecular Biology and Biophysics, Eidgenössische Technische Hochschule (ETH) Zürich, Zürich, Switzerland; International Advanced Research and Education Organization (IAREO), Tohoku University, Miyagi, Japan; Molecular Function & Life Siciences, Aichi University of Education, Aichi, Japan.
Cytoskeleton (Hoboken). 2014 Jul;71(7):412-22. doi: 10.1002/cm.21180. Epub 2014 Jul 2.
The mechanism by which the two different heads of the ciliary outer dynein arm produce force to translocate the microtubule during beating is still unknown. In this report we use cryo-electron tomography and image processing to analyze the conformational changes and the relative abundance of each conformation of the two dynein heads from mouse respiratory cilia. In the absence of nucleotides the majority of dynein dimers are in the apo form and both heads are tightly packed, whereas they are dissociated and move independently in the presence of nucleotides. The head of the external outer arm dynein heavy chain has a diagonal shift toward both the neighboring B-tubule and the proximal end of the axoneme, while the head of the internal heavy chain shifts only longitudinally toward the proximal end. In the presence of nucleotides a significant number of the dynein dimers have two heads overlapped in the proximal shifting form or overlapped in the apo form. During ciliary bending axonemal dynein translocates microtubules by moving with short steps and two heads stay at the same position longer than cytoplasmic dynein. This demonstrates that the step of the outer arm dynein dimer is not dominated by the hand-over-hand motion, but also indicates the difference between axonemal dynein and cytoplasmic dynein.
在纤毛摆动过程中，睫状体外动力蛋白臂的两个不同头部产生力以使微管移位的机制仍然未知。在本报告中，我们使用冷冻电子断层扫描和图像处理来分析来自小鼠呼吸道纤毛的两种动力蛋白头部的构象变化以及每种构象的相对丰度。在没有核苷酸的情况下，大多数动力蛋白二聚体处于脱辅基形式，两个头部紧密堆积，而在有核苷酸存在时它们会解离并独立移动。外侧外臂动力蛋白重链的头部向相邻的B微管和轴丝近端都有对角线移位，而内侧重链的头部仅纵向向近端移位。在有核苷酸存在时，大量动力蛋白二聚体的两个头部以近端移位形式重叠或以脱辅基形式重叠。在纤毛弯曲过程中，轴丝动力蛋白通过短步移动使微管移位，并且两个头部在同一位置停留的时间比胞质动力蛋白更长。这表明外臂动力蛋白二聚体的步移并不以交替移动为主，同时也表明了轴丝动力蛋白和胞质动力蛋白之间的差异。
