EFFECT OF SYNEXIN ON AGGREGATION AND FUSION OF CHROMAFFIN GRANULE GHOSTS AT PH 6
EFFECT OF SYNEXIN ON AGGREGATION AND FUSION OF CHROMAFFIN GRANULE GHOSTS AT PH 6
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DOI：
10.1016/0005-2736(87)90221-5
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发表时间：
1987-10-02
期刊：
影响因子：
--
通讯作者：
POLLARD, HB
中科院分区：
文献类型：
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作者：
NIR, S;STUTZIN, A;POLLARD, HB
在pH 6，37 ℃下，通过突触蛋白诱导嗜铬颗粒影的融合。C，在10-7 M Ca ~（2+）存在下。为了研究这种融合过程的动力学和程度，我们采用了两种测定法，其通过荧光强度增加连续监测含水内容物的混合或膜混合。在这两个试验中，嗜铬颗粒鬼被标记在膜上或在所包括的水相中。空白与标记嗜铬颗粒血影的比率在1至10之间变化。结果进行了分析的质量作用动力学模型，该模型认为，作为一个序列的第二阶的聚集过程，然后由第一级融合反应的整体融合反应。模型计算给出了公平的模拟和预测的实验结果。描述膜混合的速率常数比体积混合的速率常数大2倍以上。分析还表明，最初的聚集和融合过程，直到二聚体形成，是非常快的。聚集的速率常数接近扩散控制过程中的极限，而融合速率常数与在pH 5下最快的病毒-脂质体融合事件中发现的相同。一个小的体积增加被发现伴随着嗜铬颗粒鬼之间的融合。使用0.13、0.41和1.15的突触蛋白与嗜铬颗粒影蛋白的比率表明，中间（0.41）情况下的总体融合率更大。分析表明，synexin的主要活性是增强聚集速率。在中间或exressive synexin浓度，分别促进适度，或抑制实际的融合步骤。
Fusion of chromaffin granule ghosts was induced by synexin at pH 6, 37.degree. C, in the presence of 10-7 M Ca2+. To study the kinetics and extent of this fusion process we employed two assays that monitored continuously mixing of aqueous contents or membrane mixing by fluorescence intensity increases. In both assays chromaffin granule ghosts were either labeled on the membrane or in the included aqueous phase. The ratios of blank to labeled chromaffin granule ghosts were varied from 1 to 10. The results were analyzed in terms of a mass action kinetic model, which views the overall fusion reaction as a sequence of a second-order process of aggregation followed by a first-order fusion reaction. The model calculations gave fair simulations and predictions of the experimental results. The rate constants describing membrane mixing are more than 2-fold larger than those for volume mixing. The analysis also indicated that the initial aggregation and fusion processes, up to dimer formation, were extremely fast. The rate constant of aggregation was close to the limit in diffusion-controlled processes, whereas the fusion rate constant was about the same as found in fastest virus-liposome fusion events at pH 5. A small increase in volume was found to accompany the fusion between chromaffin granule ghosts. Using ratios of synexin to chromaffin granule ghost protein of 0.13, 0.41 and 1.15 indicated that the overall fusion rate was larger for the intermediate (0.41) case. The analysis showed that the main activity of synexin was an enhancement of the rate of aggregation. At intermediate or excressive synexin concentrations it, respectively, promoted moderately, or inhibited the actual fusion step.