beta-Spectrin limits alpha-spectrin assembly on membranes following synthesis in a chicken erythroid cell lysate.
beta-Spectrin limits alpha-spectrin assembly on membranes following synthesis in a chicken erythroid cell lysate.
复制标题
β-血影蛋白在鸡类红细胞裂解液中合成后，限制了 α-血影蛋白在膜上的组装。
作者：
R. Moon;E. Lazarides
血影蛋白是红细胞皮质下肌动蛋白网络的主要蛋白质，它包含两个不同的亚基，即α和β(参考文献1，2)。血影蛋白通过β-血影蛋白与外源蛋白Ankyrin的结合间接地与跨膜阴离子转运蛋白结合。在鸡胚红系细胞中，α-血影蛋白的合成是β-血影蛋白的三倍，尽管这两个亚基是以等摩尔量组装的。为了研究等摩尔量的血影蛋白的组装规律，现已建立了一套鸡胚红系细胞体外合成和组装的系统，该系统可以将血影蛋白的合成和组装解偶联并分别进行研究。在体外翻译了三倍于β-血影蛋白的α-血影蛋白后，95%的β-血影蛋白和等摩尔量的α-血影蛋白翻译后与去血影蛋白的兔红细胞膜结合，而多余的α-血影蛋白保持不结合。这种α-血影蛋白不能与随后添加到裂解物中的血影蛋白耗尽的质膜结合。因此，α-血影蛋白的组装受到β-血影蛋白可用性的限制，这两个亚基都是在翻译后组装的。
Spectrin, the major protein of the subcortical actin network in erythrocytes, contains two non-identical subunits, alpha and beta (refs 1, 2). Spectrin is indirectly associated with the transmembrane anion transporter through the binding of beta-spectrin to an extrinsic protein, ankyrin. In chicken embryo erythroid cells, alpha-spectrin is synthesized in a threefold excess relative to beta-spectrin, although the two subunits are assembled in equimolar amounts. To investigate the regulation of assembly of equimolar amounts of spectrin, an in vitro system from chicken embryo erythroid cells has now been developed where synthesis and assembly of spectrin can be uncoupled and studied separately. Following the in vitro translation of threefold more alpha- than beta-spectrin, 95% of the beta-spectrin and equimolar amounts of alpha-spectrin bind post-translationally to spectrin-depleted rabbit red blood cell membranes, and the excess alpha-spectrin remains unbound. This alpha-spectrin cannot bind spectrin-depleted plasma membranes subsequently added to the lysate. The assembly of alpha-spectrin is, therefore, limited by the availability of beta-spectrin, and both subunits assemble post-translationally.