Cell
Volume 179, Issue 4, 31 October 2019, Pages 909-922.e12
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Article
Structure of the Decorated Ciliary Doublet Microtubule

https://doi.org/10.1016/j.cell.2019.09.030Get rights and content
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Highlights

  • High-resolution cryo-EM structure of a native axonemal doublet microtubule

  • Atomic model for the 48-nm repeat structure includes 38 proteins

  • Coherent register between different periodicities via interconnected networks

  • Insights into diverse MIP functions and roles in ciliopathies

Summary

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.

Keywords

cilia
axoneme
doublet microtubule
tubulin
cryo-EM

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