SUBSTOICHIOMETRIC BINDING OF TAXOL SUPPRESSES MICROTUBULE DYNAMICS
SUBSTOICHIOMETRIC BINDING OF TAXOL SUPPRESSES MICROTUBULE DYNAMICS
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DOI：
10.1021/bi00007a014
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发表时间：
1995-02-21
期刊：
影响因子：
2.9
通讯作者：
JORDAN, MA
中科院分区：
文献类型：
--
作者：
DERRY, WB;WILSON, L;JORDAN, MA
我们在体外实验中测量了紫杉醇（10 nM ~ 1 μ M）对牛脑微管末端生长和缩短动力学的影响，并将其与微管中紫杉醇与微管蛋白结合的化学计量学以及微管聚合物质量的变化联系起来。结果表明，紫杉醇对微管动力学不稳定性的抑制作用取决于紫杉醇与微管结合的化学计量。在最低的有效浓度（小于或等于100 nM）下，紫杉醇与微管中微管蛋白的亚化学量结合（在0.001至0.01 mol结合紫杉醇/mol微管中微管蛋白之间）有效且选择性地抑制了与微管聚合物质量增加（28%至60%）相关的正端缩短速率和程度。在中等紫杉醇浓度（100 nM至1 μ M之间）下，额外的紫杉醇分子与微管的结合（在0.01至0.1 mol紫杉醇结合/mol微管中的微管蛋白之间）抑制了微管两端的生长和缩短事件，而微管聚合物质量没有额外增加。在高紫杉醇浓度和高紫杉醇结合化学计量（大于或等于1 μ M紫杉醇和大于或等于0.1 mol紫杉醇结合/mol微管中的微管蛋白）下，微管质量急剧增加，动力学几乎完全被抑制。这些数据支持这样的假设，即紫杉醇分子与微管中微管蛋白亚基的结合会引起该亚基的构象变化，当亚基暴露在微管末端时，该亚基的解离能力会大大降低。
We have measured the effects of taxol (10 nM to 1 mu M) on the growing and shortening dynamics at the ends of individual bovine brain microtubules in vitro and have correlated the effects both with the stoichiometry of taxol binding to tubulin in microtubules and with the changes in the microtubule polymer mass. The results indicate that taxol suppresses microtubule dynamic instability differently depending upon the stoichiometry of taxol binding to the microtubules. At the lowest effective concentrations (less than or equal to 100 nM), substoichiometric binding of taxol to tubulin in microtubules (between 0.001 and 0.01 mol of bound taxol/mol of tubulin in microtubules) potently and selectively suppresses the rate and extent of shortening at plus ends in association with some increase (28% to 60%) in the mass of microtubule polymer. At intermediate taxol concentrations (between 100 nM and 1 mu M), the binding of additional taxol molecules to the microtubules (between 0.01 and 0.1 mol of taxol bound/mol of tubulin in microtubules) inhibits both growing and shortening events at both microtubule ends with no additional increase in microtubule polymer mass, At high taxol concentrations and high taxol binding stoichiometries (greater than or equal to 1 mu M taxol and greater than or equal to 0.1 mol of taxol bound/mol of tubulin in microtubules), microtubule mass increases sharply and dynamics is almost completely suppressed. The data support the hypothesis that binding of a molecule of taxol to a tubulin subunit in microtubules induces a conformational change in that subunit that strongly reduces its ability to dissociate when the subunit becomes exposed at the microtubule end.