Microtubule assembly dynamics at the nanoscale
Microtubule assembly dynamics at the nanoscale
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DOI：
10.1016/j.cub.2007.07.011
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发表时间：
2007-09-04
期刊：
影响因子：
9.2
通讯作者：
Hunt, Alan J.
中科院分区：
文献类型：
--
作者：
Schek, Henry T., III;Gardner, Melissa K.;Hunt, Alan J.
背景资料：微管的不稳定性质对于建立细胞形态和运动性至关重要，但组装的分子基础仍不清楚。在这里，我们使用光镊跟踪微管聚合对微制造的障碍，允许前所未有的空间resolution.Results：我们发现，微管表现出广泛的纳米尺度的变化，在生长速率和经常经历缩短的游览，在某些情况下超过五个微管蛋白层，在整个净增长期间。这一结果表明三磷酸鸟苷（GTP）帽并不像之前提出的那样以单层形式存在。我们还发现，长度增量（超过100 ms的时间间隔，n = 16，762）很小，0.81 +/- 6.60 nm（平均值+/-标准差），很少超过16 nm（约两个二聚体长度），表明组装几乎完全通过单亚基添加而不是通过寡聚体发生，如最近所建议的。最后，组装率仅弱依赖于负载，与平均增长率仅下降2倍的力增加7倍，从0.4 pN到2.8 pN.Conclusions：数据是一致的机械化学模型，在空间上扩展的GTP帽允许大幅缩短纳米尺度，同时在大多数情况下仍然防止完全的灾难。
Background: The labile nature of microtubules is critical for establishing cellular morphology and motility, yet the molecular basis of assembly remains unclear. Here we use optical tweezers to track microtubule polymerization against microfabricated barriers, permitting unprecedented spatial resolution.Results: We find that microtubules exhibit extensive nanometer-scale variability in growth rate and often undergo shortening excursions, in some cases exceeding five tubulin layers, during periods of overall net growth. This result indicates that the guanosine triphosphate (GTP) cap does not exist as a single layer as previously proposed. We also find that length increments (over 100 ms time intervals, n = 16,762) are small, 0.81 +/- 6.60 nm (mean +/- standard deviation), and very rarely exceed 16 nm (about two dimer lengths), indicating that assembly occurs almost exclusively via single-subunit addition rather than via oligomers as was recently suggested. Finally, the assembly rate depends only weakly on load, with the average growth rate decreasing only 2-fold as the force increases 7-fold from 0.4 pN to 2.8 pN.Conclusions: The data are consistent with a mechanochemical model in which a spatially extended GTP cap allows substantial shortening on the nanoscale, while still preventing complete catastrophe in most cases.