Morris S J, Costello M J, Robertson J D, Südhof T C, Odenwald W F, Haynes D H
J Auton Nerv Syst. 1983 Jan;7(1):19-33. doi: 10.1016/0165-1838(83)90066-8.
Rapid freeze/freeze-fracture and thin section electron micrographic studies of the Ca2+-promoted aggregation and fusion of isolated bovine adrenal medullary chromaffin granule membranes show that the granules undergo a series of morphological changes. The contact region becomes quite extensive and the membrane curvature changes radically at the edge of the contact site. The core material retracts away from the contact site leaving an electron lucent "stripe"; however, it remains adjacent to the membrane in the non-contact areas. The pentalaminar double membrane of the contact region often shows breaks. Close examination reveals that the two granule membranes have fused and become one continuous membrane. Rearrangement of large membrane associated particles (MAPs) can be seen by freeze fracture after Ca2+-promoted granule-granule contact. The broken pentalaminar septum becomes smaller and may break down into globular structures. These observations suggest a series of reactions in which the granules first form an encounter complex, then a stable complex. The membranes within the contact region undergo lateral displacement of the proteins and phase separations of the lipids, and then fuse. Analysis of the kinetics of turbidity and fluorescence changes during granule aggregation and fusion support the main postulates of the model. The initial events of aggregation are facilitated by putative recognition proteins and K+ will promote all activities except fusion. Recent observations that several soluble proteins (synexin, and albumin) will act as fusogens are discussed in terms of the relevance to exocytosis in vivo.
对钙离子促进的分离牛肾上腺髓质嗜铬颗粒膜聚集和融合进行快速冷冻/冷冻断裂及超薄切片电子显微镜研究表明，颗粒经历了一系列形态变化。接触区域变得相当广泛，接触位点边缘的膜曲率发生了根本性变化。核心物质从接触位点缩回，留下一个电子透明的“条带”；然而，它在非接触区域仍与膜相邻。接触区域的五片层双膜常常出现断裂。仔细观察发现，两个颗粒膜已经融合并变成了一个连续的膜。钙离子促进颗粒 - 颗粒接触后，通过冷冻断裂可以看到与膜相关的大颗粒（MAPs）发生了重排。断裂的五片层隔膜变小，并可能分解成球状结构。这些观察结果表明存在一系列反应，其中颗粒首先形成相遇复合物，然后形成稳定复合物。接触区域内的膜经历蛋白质的侧向位移和脂质的相分离，然后融合。对颗粒聚集和融合过程中浊度和荧光变化动力学的分析支持了该模型的主要假设。聚集的初始事件由假定的识别蛋白促进，钾离子将促进除融合之外的所有活动。近期关于几种可溶性蛋白（突触结合蛋白和白蛋白）可作为融合剂的观察结果，根据其与体内胞吐作用的相关性进行了讨论。
