Chrétien D, Fuller S D, Karsenti E
European Molecular Biology Laboratory, Heidelberg, Germany.
J Cell Biol. 1995 Jun;129(5):1311-28. doi: 10.1083/jcb.129.5.1311.
Observation of microtubule growth at different rates by cryo-electron microscopy reveals that the ends range from blunt to long, gently curved sheets. The mean sheet length increases with the growth rate while the width of the distributions increases with the extent of assembly. The combination of a concentration dependent growth rate of the tubulin sheet with a variable closure rate of the microtubule cylinder, results in a model in which stochastic fluctuations in sheet length and tubulin conformation confine GTP-tubulins to microtubule ends. We propose that the variability of microtubule growth rate observed by video microscopy (Gildersleeve, R. F., A. R. Cross, K. E. Cullen, A. P. Fagen, and R. C. Williams. 1992. J. Biol. Chem. 267: 7995-8006, and this study) is due to the variation in the rate of cylinder closure. The curvature of the sheets at the end of growing microtubules and the small oligomeric structures observed at the end of disassembling microtubules, indicate that tubulin molecules undergo conformational changes both during assembly and disassembly.
通过冷冻电子显微镜观察不同速率下微管的生长发现，其末端形态多样，从钝端到长的、轻微弯曲的薄片不等。薄片的平均长度随生长速率增加，而分布宽度随组装程度增加。微管蛋白薄片的浓度依赖性生长速率与微管圆柱体可变的封闭速率相结合，产生了一个模型，其中薄片长度和微管蛋白构象的随机波动将GTP-微管蛋白限制在微管末端。我们认为，视频显微镜观察到的微管生长速率的变异性（Gildersleeve, R. F., A. R. Cross, K. E. Cullen, A. P. Fagen, and R. C. Williams. 1992. J. Biol. Chem. 267: 7995 - 8006，以及本研究）是由于圆柱体封闭速率的变化。生长中微管末端薄片的曲率以及解聚微管末端观察到的小寡聚结构，表明微管蛋白分子在组装和解聚过程中都发生了构象变化。
