Suprenant K A, Dentler W L
J Cell Biol. 1982 Apr;93(1):164-74. doi: 10.1083/jcb.93.1.164.
By use of dark-field light microscopy, secretory granules isolated from the anglerfish endocrine pancreas were observed to attach to and release from microtubules assembled in vitro from brain homogenates. Secretory granules only bound to microtubules assembled in the presence of microtubule-associated proteins (MAPs) and not to microtubules assembled from purified tubulin. The addition of a MAP fraction to purified tubulin restored secretory granule binding. The secretory granules were released from MAP-containing microtubules by the addition of Mg-ATP but not by other nucleotides. The number of secretory granules bound to MAP-containing microtubules was increased in the presence of cyclic AMP. In addition to the associations of secretory granules with microtubules, MAP-containing microtubules also associated with each other. These laterally associated microtubules were dispersed by the addition of Mg-ATP. Electron micrographs confirmed that the associations between MAP-containing microtubules and secretory granules as well as the associations of microtubules with one another were mediated by the high molecular weight MAPs known to project from the surface of in-vitro-assembled microtubules.
利用暗视野光学显微镜观察到，从琵琶鱼内分泌胰腺分离出的分泌颗粒能够附着于由脑匀浆体外组装的微管上，并从这些微管上释放。分泌颗粒仅与在微管相关蛋白（MAPs）存在下组装的微管结合，而不与由纯化微管蛋白组装的微管结合。向纯化的微管蛋白中添加MAP组分可恢复分泌颗粒的结合。通过添加Mg-ATP可使分泌颗粒从含MAP的微管上释放，而其他核苷酸则不能。在环磷酸腺苷存在的情况下，与含MAP微管结合的分泌颗粒数量增加。除了分泌颗粒与微管的结合外，含MAP的微管之间也相互结合。这些横向结合的微管通过添加Mg-ATP而分散。电子显微镜照片证实，含MAP微管与分泌颗粒之间的结合以及微管之间的结合是由已知从体外组装微管表面伸出的高分子量MAP介导的。
