Böhm K J, Vater W, Steinmetzer P, Unger E
Biochim Biophys Acta. 1987 Jul 6;929(2):154-63. doi: 10.1016/0167-4889(87)90171-6.
In the presence of glycerol, microtubule proteins reassemble into both microtubules and protofilament ribbons with C- and S-shaped cross-section profiles. By means of electron micrographs of cross-sectioned assemblies, we have demonstrated that, during the steady state, the percentage of ribbons, especially of C-shaped ones, decreases in favour of the formation of microtubules. The following conversion modes are discussed: A, closure of the protofilament wall by increasing its curvature; B, lateral association of C-ribbons; C, completion of C-ribbons to microtubules by lateral association of tubulin; D, disassembly of ribbons and elongation of microtubules. We conclude that ribbon disassembly proceeding in an end-wise fashion and microtubule elongation is the favoured mode of conversion. Microtubule-associated proteins were found to be required for the steady-state conversions of ribbons into microtubules. In the absence of microtubule-associated proteins, C-ribbons associate laterally, forming S-ribbons. It is shown that the protofilaments of the counter-curved parts of S-ribbons have the same polarity.
在甘油存在的情况下，微管蛋白会重新组装成具有C形和S形横截面轮廓的微管和原丝带。通过对横截面组装体的电子显微镜观察，我们证明了在稳态期间，丝带（尤其是C形丝带）的百分比会下降，有利于微管的形成。讨论了以下转换模式：A，通过增加原丝壁的曲率使其闭合；B，C形丝带的横向结合；C，通过微管蛋白的横向结合将C形丝带完成转化为微管；D，丝带的解体和微管的延长。我们得出结论，以末端方式进行的丝带解体和微管延长是最有利的转换模式。发现微管相关蛋白是丝带向微管稳态转换所必需的。在没有微管相关蛋白的情况下，C形丝带横向结合，形成S形丝带。结果表明，S形丝带反曲部分的原丝具有相同的极性。
