Beaven G H, Jean-Baptiste L, Ungewickell E, Baines A J, Shahbakhti F, Pinder J C, Lux S E, Gratzer W B
Eur J Cell Biol. 1985 Mar;36(2):299-306.
A part of the spectrin extracted from red cell membranes at low ionic strength occurs in the form of a high-molecular weight oligomeric complex with actin and proteins 4.1 and 4.9. When the extraction is performed at 35 degrees, the spectrin is present in this complex as the dimer, all higher forms being dissociated. We have been unable to establish any correlation between the fraction of the spectrin thus complexed and the metabolic state of the cell. At least a large part of the complex appears to be a defined monodisperse species, sedimenting at 31S. The actin is present as short protofilaments. The average number of spectrin molecules associated with each molecule of complex has been studied by cytochalasin binding and electron microscopy. The complexes present the appearance in the electron microscope of spiders, in which the legs are spectrin dimers, attached to a globular element, containing by inference, actin and proteins 4.1 and 4.9; they are active in nucleating the polymerization of G-actin. The complexes are extremely stable, being resistant to dissociation under the conditions of the deoxyribonuclease assay, even after treatment with trypsin to degrade the actin-associated proteins. It is suggested that the complexes represent intact junctions of the membrane cytoskeletal network. Relevant structural features of the network are revealed by electron microscopy. The results lead to inferences concerning the mechanism of dissociation of the network from the membrane.
在低离子强度下从红细胞膜中提取的部分血影蛋白以与肌动蛋白、4.1和4.9蛋白形成的高分子量寡聚复合物的形式存在。当在35摄氏度下进行提取时，血影蛋白在该复合物中以二聚体形式存在，所有更高形式均已解离。我们未能在如此复合的血影蛋白部分与细胞的代谢状态之间建立任何关联。至少大部分复合物似乎是一种确定的单分散物种，沉降系数为31S。肌动蛋白以短原纤维形式存在。已通过细胞松弛素结合和电子显微镜研究了与每个复合物分子相关的血影蛋白分子的平均数量。这些复合物在电子显微镜下呈现出蜘蛛的外观，其中的“腿”是血影蛋白二聚体，附着于一个球状元件，据推测该元件含有肌动蛋白、4.1和4.9蛋白；它们在引发G-肌动蛋白的聚合反应中具有活性。这些复合物极其稳定，即使在用胰蛋白酶处理以降解与肌动蛋白相关的蛋白质后，在脱氧核糖核酸酶测定条件下也能抗解离。有人提出，这些复合物代表膜细胞骨架网络的完整连接。网络的相关结构特征通过电子显微镜得以揭示。这些结果引发了关于网络与膜解离机制的推断。
