Rothwell S W, Grasser W A, Murphy D B
J Cell Biol. 1985 Nov;101(5 Pt 1):1637-42. doi: 10.1083/jcb.101.5.1637.
Using an immunoelectron microscopic procedure, we directly observed the concurrent addition and loss of chicken brain tubulin subunits from the opposite ends of microtubules containing erythrocyte tubulin domains. The polarity of growth of the brain tubulin on the ends of erythrocyte microtubules was determined to be similar to growth off the ends of Chlamydomonas axonemes. The flux rate for brain tubulin subunits in vitro was low, approximately 0.9 micron/h. Tubulin subunit flux did not continue through the entire microtubule as expected, but ceased when erythrocyte tubulin domains became exposed, resulting in a metastable configuration that persisted for at least several hours. We attribute this to differences in the critical concentrations of erythrocyte and brain tubulin. The exchange of tubulin subunits into the walls of preformed microtubules other than at their ends was also determined to be insignificant, the exchange rate being less than the sensitivity of the assay, or less than 0.2%/h.
运用免疫电子显微镜技术，我们直接观察到鸡脑微管蛋白亚基在含有红细胞微管蛋白结构域的微管两端同时进行添加和丢失。红细胞微管末端脑微管蛋白的生长极性被确定为与衣藻轴丝末端的生长相似。体外脑微管蛋白亚基的通量速率较低，约为0.9微米/小时。微管蛋白亚基通量并未如预期那样贯穿整个微管，而是在红细胞微管蛋白结构域暴露时停止，从而形成了一种至少持续数小时的亚稳构型。我们将此归因于红细胞和脑微管蛋白临界浓度的差异。除了微管末端之外，微管蛋白亚基与预先形成的微管壁的交换也被确定为微不足道，其交换速率低于检测灵敏度，即小于0.2%/小时。
