Calvert R, Bennett P, Gratzer W
Eur J Biochem. 1980 Jun;107(2):355-61. doi: 10.1111/j.1432-1033.1980.tb06036.x.
The subunits of spectrin from human erythrocytes were separated by ion-exchange chromatography on hydroxyapatite in the presence of urea. When renatured from the urea solution they are found to be monomeric, although the smaller subunit (band 2) is prone to aggregation. In shape, solubility and secondary structure the subunits resemble the native spectrin dimer, indicating that subunit interaction is not essential for maintaining the native conformation. When the subunits are recombined, a dimer with the sedimentation coefficient of the native species is formed. This constitutes direct evidence that native spectrin is a heterodimer, rather than a mixture containing homologous and heterologous species. The interaction of the separated subunits with the chymotryptic fragment of the spectrin-binding protein (protein 2.1, or ankyrin) of the erythrocyte membrane was studied. Only the smaller subunit has the ability to bind, and thus presumably contains the site by which the cytoskeleton is attached to the plasma membrane. On the other hand, the formation of a complex with F-actin and protein 4.1 requires the presence of both subunits. A complex of these proteins with band 2 is formed, however, when traces of an additional, as yet unidentified, protein are present.
在尿素存在的情况下，通过羟基磷灰石离子交换色谱法分离人红细胞血影蛋白的亚基。当从尿素溶液中复性时，发现它们是单体，尽管较小的亚基（带2）易于聚集。在形状、溶解性和二级结构方面，这些亚基类似于天然血影蛋白二聚体，表明亚基间相互作用对于维持天然构象并非必不可少。当亚基重新组合时，会形成具有天然物种沉降系数的二聚体。这构成了直接证据，证明天然血影蛋白是一种异源二聚体，而不是包含同源和异源物种的混合物。研究了分离的亚基与红细胞膜血影蛋白结合蛋白（蛋白2.1，即锚蛋白）的胰凝乳蛋白酶片段之间的相互作用。只有较小的亚基具有结合能力，因此推测其包含细胞骨架附着于质膜的位点。另一方面，与F-肌动蛋白和蛋白4.1形成复合物需要两个亚基都存在。然而，当存在微量额外的、尚未鉴定的蛋白质时，这些蛋白质会与带2形成复合物。
