Cilia are ubiquitous microtubule-based eukaryotic organelles that project from the cell to generate motility or function in cellular signaling. Motile cilia or flagella contain axonemal dynein motors and other complexes to achieve beating. Primary cilia are immotile and act as signaling hubs, with receptors shuttling between the cytoplasm and ciliary compartment. In both cilia types, an intraflagellar transport (IFT) system powered by unique kinesin and dynein motors functions to deliver the molecules required to build cilia and maintain their functions. Cryo-electron tomography has helped to reveal the organization of protein complex arrangement along the axoneme and the structure of anterograde IFT trains as well as the structure of primary cilia. Only recently, single-particle analysis (SPA) cryo-electron microscopy has provided molecular details of the protein organization of ciliary components, helping us to understand how they bind to microtubule doublets and how mechanical force propagated by dynein conformational changes is converted into ciliary beating. Here we highlight recent structural advances that are leading to greater knowledge of ciliary function.

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纤毛和鞭毛内运输的结构生物学

纤毛是普遍存在的基于微管的真核细胞器，它从细胞中伸出，在细胞信号传导中产生运动或功能。运动的纤毛或鞭毛含有轴丝动力蛋白马达和其他复合物来实现跳动。初级纤毛不动，充当信号中枢，受体在细胞质和纤毛室之间穿梭。在这两种纤毛类型中，由独特的驱动蛋白和动力蛋白马达驱动的鞭毛内运输（IFT）系统可传递构建纤毛并维持其功能所需的分子。冷冻电子断层扫描有助于揭示蛋白质复合物沿轴丝排列的组织、顺行 IFT 序列的结构以及初级纤毛的结构。直到最近，单颗粒分析（SPA）冷冻电子显微镜才提供了纤毛成分蛋白质组织的分子细节，帮助我们了解它们如何与微管双联体结合，以及动力蛋白构象变化传播的机械力如何转化为纤毛跳动。在这里，我们重点介绍最近的结构进展，这些进展使人们对睫状体功能有了更多的了解。