Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
MRC Harwell Institute, Harwell Campus, Oxfordshire OX11 0RD, UK.
Cell. 2021 Nov 11;184(23):5791-5806.e19. doi: 10.1016/j.cell.2021.10.007. Epub 2021 Oct 28.
Dynein-decorated doublet microtubules (DMTs) are critical components of the oscillatory molecular machine of cilia, the axoneme, and have luminal surfaces patterned periodically by microtubule inner proteins (MIPs). Here we present an atomic model of the 48-nm repeat of a mammalian DMT, derived from a cryoelectron microscopy (cryo-EM) map of the complex isolated from bovine respiratory cilia. The structure uncovers principles of doublet microtubule organization and features specific to vertebrate cilia, including previously unknown MIPs, a luminal bundle of tektin filaments, and a pentameric dynein-docking complex. We identify a mechanism for bridging 48- to 24-nm periodicity across the microtubule wall and show that loss of the proteins involved causes defective ciliary motility and laterality abnormalities in zebrafish and mice. Our structure identifies candidate genes for diagnosis of ciliopathies and provides a framework to understand their functions in driving ciliary motility.
动力蛋白装饰的二联体微管（DMT）是纤毛的振荡分子机器轴丝的关键组成部分，其内腔表面由微管内蛋白（MIP）周期性图案化。在这里，我们从牛呼吸纤毛中分离出的复合物的冷冻电镜（cryo-EM）图谱中，提供了哺乳动物 DMT 的 48nm 重复的原子模型。该结构揭示了二联体微管组织的原则和脊椎动物纤毛特有的特征，包括以前未知的 MIP、微管内腔中的 tektin 丝束和五聚体动力蛋白 docking 复合物。我们确定了一种在微管壁上桥接 48nm 到 24nm 周期性的机制，并表明相关蛋白的缺失会导致斑马鱼和小鼠的纤毛运动缺陷和偏侧性异常。我们的结构确定了纤毛病的候选诊断基因，并提供了一个框架来理解它们在驱动纤毛运动中的功能。
