SPECTRIN TETRAMER-DIMER EQUILIBRIUM AND THE STABILITY OF ERYTHROCYTE-MEMBRANE SKELETONS
SPECTRIN TETRAMER-DIMER EQUILIBRIUM AND THE STABILITY OF ERYTHROCYTE-MEMBRANE SKELETONS
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DOI：
10.1038/285586a0
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发表时间：
1980-01-01
期刊：
影响因子：
64.8
通讯作者：
PALEK, J
中科院分区：
文献类型：
--
作者：
LIU, SC;PALEK, J
红细胞膜的内侧由膜蛋白的二维网络层压而成，其中包括血影蛋白、肌动蛋白和其他一些成分1-4。从膜中提取脂质和整合蛋白后，该膜骨架可以可视化为由扭曲纤维 1-4 和球状突起 4 组成的球形网络；然而，膜骨架中各个蛋白质的组装尚不清楚。血影蛋白可以二聚体和四聚体的形式从膜上洗脱5-8。使用低角度阴影技术的电子显微镜研究表明，血影蛋白二聚体是两条平行的扭曲纤维，可能代表血影蛋白 9 的带 1 和 2。推测由两个二聚体头对头结合形成的血影蛋白四聚体的长度是其两倍9。在溶液中，血影蛋白二聚体-四聚体平衡取决于温度和盐浓度7,8；然而，尚不清楚膜中是否存在相同的平衡以及它是否影响膜的物理性质，例如其结构稳定性和可变形性。我们现在证明血影蛋白二聚体和四聚体在膜中处于可逆平衡，并且在生理条件下这种平衡有利于血影蛋白四聚体。此外，我们还发现，在低渗条件下通过幽灵孵化诱导的血影蛋白四聚体向二聚体的转化会降低 Triton 不溶性膜骨架的结构稳定性。
The inner side of the red-cell membrane is laminated by a two-dimensional network of membrane proteins which include spectrin, actin and some other components1–4. After extraction of lipids and integral proteins from the membrane, this membrane skeleton can be visualized as a ball-shaped network consisting of twisted fibres1–4and globular protrusions4; however, the assembly of the individual proteins in the membrane skeleton is not well understood. Spectrin can be eluted from the membrane in the form of dimers and tetramers5–8. Electron microscopic study with low-angle shadowing technique shows that spectrin dimers are two parallel strands of twisted fibres presumably representing bands 1 and 2 of spectrin9. Spectrin tetramers presumably formed by head-to-head associations of two dimers are twice as long9. In solution, the spectrin dimer–tetramer equilibrium depends on temperature and salt concentration7,8; however, it is not known whether the same equilibrium exists in the membrane and whether it affects the physical properties of the membrane, such as its structural stability and deformability. We now demonstrate that spectrin dimers and tetramers are in a reversible equilibrium in the membrane and that in physiological conditions this equilibrium favours spectrin tetramers. Furthermore, we show that transformation of spectrin tetramers to dimers, as induced by ghost incubation in hypotonic conditions, diminishes the structural stability of the Triton-insoluble membrane skeletons.