Childers S R, Siegel F L
Biochim Biophys Acta. 1975 Sep 9;405(1):99-108. doi: 10.1016/0005-2795(75)90319-0.
An acidic calcium-binding phosphoprotein has been isolated from a cholinergic tissue, electroplax from Electrophorus electricus. The purification procedures included (NH4)2SO4 fractionation, boiling treatment, ECTEOLA-cellulose chromatography, and gel filtration on Sephadex G-100. Experiments were performed to compare this protein and a calcium-binding protein isolated from mammalian brain, adrenal medulla, and testis. These experiments showed that the two proteins were identical in terms of molecular weight (14 000), calcium-binding dissociation constant (kd=2.1-10(-5) M), electrophoretic mobility at pH 8.7 in 15% polyacrylamide gels, and phosphorus content (1 mol phosphorus per mol protein). In addition, the two proteins had similar amino acid compositions and peptide maps. Although the electroplax protein was not present in eel skeletal muscle, preliminary experiments indicated that small amounts of the protein were present in other eel tissues, namely brain, liver and spleen. These results suggest an identity between the electroplax and mammalian calcium-binding proteins and extend the findind of comparatively large amounts of the protein from mammalian nervous tissue to a cholinergic nervous tissue, electroplax. The close similarity of the proteins suggests a conservation of structure during evolution which may be required to fulfill a role in neuronal function.
一种酸性钙结合磷蛋白已从一种胆碱能组织——电鳗的电板中分离出来。纯化步骤包括硫酸铵分级分离、煮沸处理、ECTEOLA - 纤维素层析以及在葡聚糖G - 100上的凝胶过滤。进行了实验以比较这种蛋白质与从哺乳动物脑、肾上腺髓质和睾丸中分离出的一种钙结合蛋白。这些实验表明，这两种蛋白质在分子量（14000）、钙结合解离常数（kd = 2.1×10⁻⁵ M）、在pH 8.7的15%聚丙烯酰胺凝胶中的电泳迁移率以及磷含量（每摩尔蛋白质含1摩尔磷）方面是相同的。此外，这两种蛋白质具有相似的氨基酸组成和肽图。虽然电板蛋白在鳗鱼骨骼肌中不存在，但初步实验表明，在鳗鱼的其他组织，即脑、肝和脾中存在少量这种蛋白质。这些结果表明电板蛋白与哺乳动物钙结合蛋白相同，并将从哺乳动物神经组织中发现的相对大量的这种蛋白质的发现扩展到了一种胆碱能神经组织——电板。这些蛋白质的高度相似性表明在进化过程中结构的保守性，这可能是在神经元功能中发挥作用所必需的。
