Assembly dynamics of microtubules at molecular resolution
Assembly dynamics of microtubules at molecular resolution
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DOI：
10.1038/nature04928
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发表时间：
2006-08-10
期刊：
影响因子：
64.8
通讯作者：
Dogterom, Marileen
中科院分区：
文献类型：
--
作者：
Kerssemakers, Jacob W. J.;Munteanu, E. Laura;Dogterom, Marileen
微管是高度动态的蛋白质聚合物（1），它是所有真核细胞中细胞骨架的关键组成部分。尽管已知微管由微管蛋白二聚体自组装而成，但无论是在体外（2,3）还是在体内（4,5），关于微管组装动力学的信息都局限于对数千个微管蛋白亚基的平均生长和收缩速率的测量。因此，缺乏关于导致微管末端生长和收缩的分子事件顺序的信息。在此，我们利用光镊以分子分辨率观察单个微管的组装动力学。我们发现微管几乎能瞬间增加其总长度，增加量超过单个二聚体的大小（8纳米）。当加入微管相关蛋白XMAP215（参考文献6）时，这种效应显著增强，并且观察到长度快速增加约40 - 60纳米。这些观察结果表明，小的微管蛋白寡聚体能够直接添加到生长的微管上，并且XMAP215通过促进长寡聚体的添加来加速微管生长。在微管组装过程中实现分子分辨率为直接研究许多最近发现的微管末端结合蛋白在活细胞中调节微管动力学的分子机制开辟了道路（7 - 9）。
Microtubules are highly dynamic protein polymers(1) that form a crucial part of the cytoskeleton in all eukaryotic cells. Although microtubules are known to self- assemble from tubulin dimers, information on the assembly dynamics of microtubules has been limited, both in vitro(2,3) and in vivo(4,5), to measurements of average growth and shrinkage rates over several thousands of tubulin subunits. As a result there is a lack of information on the sequence of molecular events that leads to the growth and shrinkage of microtubule ends. Here we use optical tweezers to observe the assembly dynamics of individual microtubules at molecular resolution. We find that microtubules can increase their overall length almost instantaneously by amounts exceeding the size of individual dimers ( 8 nm). When the microtubule- associated protein XMAP215 ( ref. 6) is added, this effect is markedly enhanced and fast increases in length of about 40 - 60 nm are observed. These observations suggest that small tubulin oligomers are able to add directly to growing microtubules and that XMAP215 speeds up microtubule growth by facilitating the addition of long oligomers. The achievement of molecular resolution on the microtubule assembly process opens the way to direct studies of the molecular mechanism by which the many recently discovered microtubule end-binding proteins regulate microtubule dynamics in living cells(7-9).