Tubulin tails and their modifications regulate protein diffusion on microtubules
Tubulin tails and their modifications regulate protein diffusion on microtubules
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DOI：
10.1073/pnas.1914772117
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发表时间：
2020-04-21
影响因子：
11.1
通讯作者：
Levy, Yaakov
中科院分区：
文献类型：
--
作者：
Bigman, Lavi S.;Levy, Yaakov
微管（MT）是真核生物细胞骨架的重要组成部分，是细胞内运输的“高速公路”。除了众所周知的主动运输货物的马达蛋白，许多MT结合蛋白似乎采用扩散运动作为运输机制。然而，由于目前实验技术的有限空间分辨率，蛋白质扩散的详细机制尚未阐明。特别是，微管蛋白尾部和尾部修饰在扩散过程中的确切作用尚不清楚。在这里，使用粗粒度的分子动力学模拟验证对原子模拟，我们探索蛋白质扩散的分子机制沿着MT。我们发现，静电相互作用在蛋白质扩散中起着核心作用;无序的微管蛋白尾部增强亲和力，但减慢扩散，扩散发生在离散的步骤。虽然沿着野生型MT的扩散沿着是在二聚体微管蛋白的步骤中进行的，但是尾部的去除导致单体微管蛋白的步骤。我们发现，扩散的能量势垒是较大的MT上的扩散主要是由MT尾巴，而不是MT体介导的。此外，球状蛋白（EB 1和PRC 1）比内在无序蛋白（Tau）在MT上扩散得更慢。最后，我们发现微管蛋白尾部的多聚谷氨酰化和多聚甘氨酰化导致蛋白质沿沿着MT扩散较慢，尽管多聚甘氨酰化导致跨MT原丝的更快扩散。两者合计，我们的研究结果解释了实验观察到的数据，并阐明了无序微管蛋白尾部和尾部修饰在蛋白质沿沿着MT扩散的分子机制中所起的作用。
Microtubules (MTs) are essential components of the eukaryotic cytoskeleton that serve as "highways" for intracellular trafficking. In addition to the well-known active transport of cargo by motor proteins, many MT-binding proteins seem to adopt diffusional motility as a transportation mechanism. However, because of the limited spatial resolution of current experimental techniques, the detailed mechanism of protein diffusion has not been elucidated. In particular, the precise role of tubulin tails and tail modifications in the diffusion process is unclear. Here, using coarse-grained molecular dynamics simulations validated against atomistic simulations, we explore the molecular mechanism of protein diffusion along MTs. We found that electrostatic interactions play a central role in protein diffusion; the disordered tubulin tails enhance affinity but slow down diffusion, and diffusion occurs in discrete steps. While diffusion along wild-type MT is performed in steps of dimeric tubulin, the removal of the tails results in a step of monomeric tubulin. We found that the energy barrier for diffusion is larger when diffusion on MTs is mediated primarily by the MT tails rather than the MT body. In addition, globular proteins (EB1 and PRC1) diffuse more slowly than an intrinsically disordered protein (Tau) on MTs. Finally, we found that polyglutamylation and polyglycylation of tubulin tails lead to slower protein diffusion along MTs, although polyglycylation leads to faster diffusion across MT protofilaments. Taken together, our results explain experimentally observed data and shed light on the roles played by disordered tubulin tails and tail modifications in the molecular mechanism of protein diffusion along MTs.