Microtubules are cytoskeletal structures involved in stability, transport and organization in the cell. The building blocks, the α- and β-tubulin heterodimers, form protofilaments that associate laterally into the hollow microtubule. Microtubule also exists as highly stable doublet microtubules in the cilia where stability is needed for ciliary beating and function. The doublet microtubule maintains its stability through interactions at its inner and outer junctions where its A- and B-tubules meet. Here, using cryo-electron microscopy, bioinformatics and mass spectrometry of the doublets of Chlamydomonas reinhardtii and Tetrahymena thermophila, we identified two new inner junction proteins, FAP276 and FAP106, and an inner junction-associated protein, FAP126, thus presenting the complete answer to the inner junction identity and localization. Our structural study of the doublets shows that the inner junction serves as an interaction hub involved tubulin post-translational modification. These interactions contribute to the stability of the doublet and hence, normal ciliary motility.

中文翻译：

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纤毛的内部连接复合体是一个相互作用枢纽，涉及微管蛋白的翻译后修饰

微管是参与细胞稳定性，转运和组织的细胞骨架结构。α-和β-微管蛋白异二聚体的结构单元形成原丝，其横向结合到中空微管中。微管还作为纤毛中高度稳定的双态微管存在，其中纤毛的跳动和功能需要稳定性。双重微管通过其A管和B管相遇的内部和外部连接处的相互作用来维持其稳定性。在这里，使用冷冻电子显微镜，莱茵衣 藻和嗜热四膜虫的双峰的生物信息学和质谱法，我们鉴定了两个新的内部连接蛋白FAP276和FAP106，以及一个内部连接相关蛋白FAP126，从而为内部连接身份和定位提供了完整的答案。我们对二联体的结构研究表明，内部连接充当了微管蛋白翻译后修饰的相互作用中心。这些相互作用有助于双联体的稳定性，从而促进正常的睫状运动。