How calcium causes microtubule depolymerization.
How calcium causes microtubule depolymerization.
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DOI：
10.1002/(sici)1097-0169(1997)36:2
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发表时间：
1997
影响因子：
--
通讯作者：
E. T. O'Brien;E. Salmon;H. Erickson
中科院分区：
文献类型：
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作者：
E. T. O'Brien;E. Salmon;H. Erickson
钙（Ca）的影响进行了评估，使用视频增强微分干涉相差光学显微镜在体外个别微管。猪脑微管蛋白的磷酸纤维素纯化（PC）和微管相关蛋白（MAP）的制剂中组装在精子轴丝片段的流动室和微管的生长和缩短的模式进行了观察。然后将微管蛋白加Ca加入到腔室中并继续观察。钙促进微管的解体，特别是促进灾难反应在PC和MAP-含有微管，没有明显的变化，在伸长率。对突变频率的影响在高于0.5 mM游离Ca时非常迅速地增加，这意味着可能的协同效应。救援率仍然非常高后，钙添加在含MAP的微管，缩短率不变，而在磷酸纤维素纯化的微管，救援出现减少钙添加和缩短率增加4至6倍。这些结果表明，钙可以直接不稳定增长的微管末端，而不改变游离微管蛋白的有效浓度，这种效果可以看到，即使对背景的动力学的深刻差异所赋予的微管相关蛋白。在GTP帽的模型内考虑，结果暗示高Ca可能起作用以增加帽内GTP水解的速率。
The effects of calcium (Ca) were assessed using video-enhanced differential interference contrast light microscopy on individual microtubules in vitro. Phosphocellulose-purified (PC) and microtubule associated protein (MAP)-containing preparations of porcine brain tubulin were assembled in a flow chamber onto sperm axoneme fragments and the pattern of growth and shortening of the microtubules was observed. Tubulin plus Ca was then added to the chamber and observation continued. Ca promoted the disassembly of microtubules by specifically promoting the catastrophe reaction in both PC- and MAP-containing microtubules, without an appreciable change in elongation rate. The effect on catastrophe frequency increased very rapidly above 0.5 mM free Ca, implying a possible cooperative effect. The rescue rate remained very high after Ca addition in MAP-containing microtubules, and the shortening rate was unchanged, while in phosphocellulose-purified microtubules, rescue appeared to be decreased by Ca addition and shortening rates increased 4 to 6-fold. These results illustrate that Ca can directly destabilize growing microtubule ends without changing the effective concentration of free tubulin, and that this effect can be seen even against the background of the profound differences in dynamics conferred by the microtubule-associated proteins. Considered within models of the GTP cap, the results imply that high Ca may act to increase the rate of GTP hydrolysis within the cap.