Flagellar microtubule doublet assembly in vitro reveals a regulatory role of tubulin C-terminal tails
Flagellar microtubule doublet assembly in vitro reveals a regulatory role of tubulin C-terminal tails
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DOI：
10.1126/science.aav2567
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发表时间：
2019-01
期刊：
影响因子：
56.9
通讯作者：
Marketa Schmidt-Cernohorska;I. Zhernov;Emmanuelle Steib;M. L. Guennec;R. Achek;S. Borgers;Davide Demurtas;L. Mouawad;Zdeněk Lánský;Virginie Hamel;Paul Guichard
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文献类型：
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作者：
Marketa Schmidt-Cernohorska;I. Zhernov;Emmanuelle Steib;M. L. Guennec;R. Achek;S. Borgers;Davide Demurtas;L. Mouawad;Zdeněk Lánský;Virginie Hamel;Paul Guichard
纤毛是一种保守的细胞器，对于运动以及感知细胞外环境至关重要。其核心结构的特点是由9个微管双联体（MTD）。MTD组装的机制尚不清楚。Schmidt-Cernohorska等人开发了一种体外重建MTD组装体的试验。微管蛋白羧基末端尾在MTD形成中起关键的抑制作用。分子动力学表明，羧基端尾的A11微管原丝调节MTD启动。此外，活细胞成像显示MTD的意外双向各向同性伸长。微管蛋白的内在相互作用特性为鞭毛微管双联体组装提供了结构基础。微管双联体（MTDs），由一个完整的A-微管表面的一个不完整的B-微管组成，提供了一个结构支架介导鞭毛内运输和纤毛跳动。尽管MTD的基本作用，其形成的分子机制是未知的。我们使用无细胞测定来证明微管蛋白的羧基末端（C末端）尾在MTD组装中的关键抑制作用。去除组装的A-微管的C-末端尾部允许B-微管在其表面上成核。只有一个A-微管原丝的C-末端尾巴抑制这种侧表面微管蛋白的相互作用，这将在体内克服结合蛋白伴侣。B-微管成核和其独特的各向同性伸长的动力学阐明通过使用现场成像。因此，微管蛋白的固有相互作用性质提供了驱动鞭毛MTD组装的结构基础。
Assembly of the ciliary microtubule doublet The cilium is a conserved organelle that is crucial for motility as well as for sensing the extracellular environment. Its core structure is characterized by nine microtubule doublets (MTDs). The mechanisms of MTD assembly are unclear. Schmidt-Cernohorska et al. developed an assay to reconstitute MTD assembly in vitro. Tubulin carboxyl-terminal tails played a critical inhibitory role in MTD formation. Molecular dynamics revealed that carboxyl-terminal tails of the A11 microtubule protofilament regulated MTD initiation. Furthermore, live-cell imaging showed an unexpected bidirectional isotropic elongation of the MTD. Science, this issue p. 285 Inherent interaction properties of tubulin provide a structural basis for flagellar microtubule doublet assembly. Microtubule doublets (MTDs), consisting of an incomplete B-microtubule at the surface of a complete A-microtubule, provide a structural scaffold mediating intraflagellar transport and ciliary beating. Despite the fundamental role of MTDs, the molecular mechanism governing their formation is unknown. We used a cell-free assay to demonstrate a crucial inhibitory role of the carboxyl-terminal (C-terminal) tail of tubulin in MTD assembly. Removal of the C-terminal tail of an assembled A-microtubule allowed for the nucleation of a B-microtubule on its surface. C-terminal tails of only one A-microtubule protofilament inhibited this side-to-surface tubulin interaction, which would be overcome in vivo with binding protein partners. The dynamics of B-microtubule nucleation and its distinctive isotropic elongation was elucidated by using live imaging. Thus, inherent interaction properties of tubulin provide a structural basis driving flagellar MTD assembly.