The axoneme of motile cilia is the largest macromolecular machine of eukaryotic cells. In humans, impaired axoneme function causes a range of ciliopathies. Axoneme assembly, structure, and motility require a radially arranged set of doublet microtubules, each decorated in repeating patterns with non-tubulin components. We use single-particle cryo-electron microscopy to visualize and build an atomic model of the repeating structure of a native axonemal doublet microtubule, which reveals the identities, positions, repeat lengths, and interactions of 38 associated proteins, including 33 microtubule inner proteins (MIPs). The structure demonstrates how these proteins establish the unique architecture of doublet microtubules, maintain coherent periodicities along the axoneme, and stabilize the microtubules against the repeated mechanical stress induced by ciliary motility. Our work elucidates the architectural principles that underpin the assembly of this large, repetitive eukaryotic structure and provides a molecular basis for understanding the etiology of human ciliopathies.

中文翻译：

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装饰性睫状双子微管的结构。

运动纤毛的轴突是真核细胞最大的大分子机器。在人类中，轴突功能受损会导致一系列的纤毛病。轴突的组装，结构和运动性需要径向排列的一组双态微管，每个微管以重复的形式装饰有非微管蛋白成分。我们使用单粒子冷冻电子显微镜可视化并构建天然轴突双峰微管重复结构的原子模型，该模型揭示了38个相关蛋白（包括33个微管内部蛋白）的身份，位置，重复长度和相互作用。 MIP）。该结构说明了这些蛋白质如何建立双重态微管的独特结构，如何沿着轴突保持连贯的周期性，并稳定微管以抵抗由睫状运动引起的反复机械应力。我们的工作阐明了支撑这种大的重复性真核生物结构的结构原理，并为理解人类纤毛病的病因提供了分子基础。