Dynamic instability of microtubules assembled from microtubule-associated protein-free tubulin: neither variability of growth and shortening rates nor "rescue" requires microtubule-associated proteins.
Dynamic instability of microtubules assembled from microtubule-associated protein-free tubulin: neither variability of growth and shortening rates nor "rescue" requires microtubule-associated proteins.
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由无微管相关蛋白的微管蛋白组装而成的微管的动态不稳定性：生长和缩短率的变化和“拯救”都不需要微管相关蛋白。
DOI：
10.1021/bi9616965
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Bhatacharjee,G
中科院分区：
文献类型：
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作者：
Billger,MA;Bhattacharjee,G;WilliamsJr,RC;Bhatacharjee,G
微管相关蛋白（MAPs）是微管在动态不稳定状态下生长和缩短的重要调控因子。对动态不稳定性机制的充分理解需要区分哪些方面是由微管相关蛋白介导的（即使是在小的残留浓度下），哪些是微管蛋白晶格本身的内在特性。本文讨论了其中的两个方面：MAP是否会导致动态不稳定的救援事件（即，从缩短到生长的转变）以及MAP是否是微管生长和缩短速率显著变化的原因。通过磷酸纤维素和DEAE-Sephadex连续色谱法制备非常纯的微管蛋白。电泳和免疫印迹分析表明，它基本上是MAP-免费的，它含有少于一个MAP分子每10 000微管蛋白二聚体。当通过视频DIC显微镜研究其动态不稳定性时，发现救援发生的平均频率为每4 μm缩短1次。在几微米的长度尺度上观察到的生长和缩短速率的变异性并没有因为去除MAPs而改变。由于在这些实验中计算的结合MAP分子之间的平均距离大于14 μm，因此可以得出结论，它们不会引起速率的挽救或变异性。
The growth and shortening of microtubules in dynamic instability is known to be modulated by microtubule-associated proteins (MAPs). A full understanding of the mechanism of dynamic instability requires that one distinguish which of its aspects are mediated by microtubule-associated proteins (even in small residual concentrations) and which are intrinsic properties of the tubulin lattice itself. This paper addresses two of those aspects: whether MAPs cause the rescue events of dynamic instability (i.e., the transitions from shortening to growth) and whether MAPs are responsible for the marked variability of the rates at which microtubules grow and shorten. Very pure tubulin was prepared by sequential chromatographies on phosphocellulose and DEAE-Sephadex. Analysis by electrophoresis and immunoblotting showed it to be essentially MAP-free; it contained fewer than one MAP molecule per 10 000 tubulin dimers. When its dynamic instability was studied by video-DIC microscopy, rescues were found to occur at a mean frequency of one per 4 μm of shortening. Variability of rates of growth and shortening, which is observed on the length scale of a few micrometers, was not changed by removal of MAPs. Because the mean distance between bound MAP molecules was calculated to be greater than 14 μm in these experiments, it is concluded that they cannot cause either rescue or variability of rates.