Südhof T C, Walker J H, Obrocki J
EMBO J. 1982;1(10):1167-70. doi: 10.1002/j.1460-2075.1982.tb00008.x.
Calelectrin is a protein that can be purified to homogeneity from the cholinergically innervated electric organ of Torpedo marmorata where it is present in large amounts. It has been shown to bind to the membranes of the electric organ in a Ca2+-dependent and specific manner. Using the purified protein we now report that it is specifically self-aggregated by Ca2+ in micromolar concentrations but not by Mg2+ at much higher concentrations. Sr2+ is also completely inactive, while Ba2+ and the trivalent lanthanides Tb3+, Eu3 +, and La3+ can substitute for Ca2+. Calelectrin also greatly enhances the Ca2+-induced aggregation of isolated synaptic vesicle membranes from the cholinergic nerve terminals of T. marmorata and of chromaffin granule membranes from the bovine adrenal medulla. The potentiation of membrane aggregation is mainly due to the appearance of a fast aggregatory phase in the presence of calelectrin . It is saturable with respect to calelectrin and can be demonstrated at very low calelectrin concentrations, suggesting a specific calelectrin membrane-binding component. This component seems to be of lipid nature since the aggregation of total extracted lipids from Torpedo electric organ and from chromaffin granules could also be enhanced by calelectrin . The Ca2+-induced self-association of calelectrin and its aggregation enhancing effect may be of great importance to the structural organization of neural and secretory cells and the mechanism of exocytosis.
钙电蛋白是一种可从多斑电鳐胆碱能神经支配的电器官中纯化至同质的蛋白质，该器官中大量存在这种蛋白质。已证明它以钙依赖且特异的方式与电器官的膜结合。利用纯化的该蛋白质，我们现在报告，它在微摩尔浓度下被钙离子特异性地自我聚集，而在高得多的浓度下不被镁离子聚集。锶离子也完全无活性，而钡离子和三价镧系元素铽离子、铕离子和镧离子可替代钙离子。钙电蛋白还极大地增强了来自多斑电鳐胆碱能神经末梢的分离突触小泡膜以及来自牛肾上腺髓质嗜铬颗粒膜的钙离子诱导的聚集。膜聚集的增强主要归因于在有钙电蛋白存在时出现快速聚集阶段。它对钙电蛋白是可饱和的，并且在非常低的钙电蛋白浓度下即可显示，提示存在一种特异的钙电蛋白膜结合成分。该成分似乎具有脂质性质，因为来自电鳐电器官和嗜铬颗粒的总提取脂质的聚集也可被钙电蛋白增强。钙电蛋白的钙离子诱导的自缔合及其聚集增强作用可能对神经细胞和分泌细胞的结构组织以及胞吐作用机制非常重要。
