Phosphatidylserine binding sites in erythroid spectrin: Location and implications for membrane stability
Phosphatidylserine binding sites in erythroid spectrin: Location and implications for membrane stability
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DOI：
10.1021/bi035653h
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发表时间：
2004-01-20
期刊：
影响因子：
2.9
通讯作者：
Mohandas, N
中科院分区：
文献类型：
--
作者：
An, XL;Guo, XH;Mohandas, N
红细胞膜是一种复合结构，由连接到血影蛋白膜骨架的脂质双层组成。已知血影蛋白与其他蛋白质的两种复合物参与附着。血影蛋白也被证明与磷脂酰丝氨酸（PS），脂质双层的组成部分，这是局限于其内部小叶相互作用。在血影蛋白序列中可能有多个与PS相互作用的位点，但迄今为止尚未确定。在这里，我们探讨了含PS的脂质体与天然α-和β-血影蛋白链的相互作用，并与重组血影蛋白片段，包括两条链的整个序列。我们发现，α-血影蛋白和β-血影蛋白结合PS和高亲和力的网站位于8的38个三螺旋结构重复，构成了大部分的两条链，这些是α 8，α 9 -10，β 2，β 3，β 4，β 12，β 13，和β 14，和PS的亲和力也被发现在非同源的N-末端结构域的β链。任何一条链的其他片段都没有显示出明显的结合。血影蛋白及其组成链与PS和磷脂酰胆碱（PC）混合脂质体的结合依赖于PS的比例。血影蛋白二聚体与PS脂质体的结合被含有PS结合位点的单重复序列抑制。值得注意的是，β-血影蛋白中的PS结合位点与锚蛋白和4.1R的连接位点非常接近，锚蛋白和4.1R是参与血影蛋白与膜连接的蛋白质。我们推测血影蛋白与PS在膜中的直接相互作用可能会调节其与蛋白质的相互作用，并且（也考虑到已知的4.1R对PS的亲和力）可能导致在红细胞膜中观察到的富含PS的脂质结构域的形成。
The erythrocyte membrane is a composite structure consisting of a lipid bilayer tethered to the spectrin-based membrane skeleton. Two complexes of spectrin with other proteins are known to participate in the attachment. Spectrin has also been shown to interact with phosphatidylserine (PS), a component of the lipid bilayer, which is confined to its inner leaflet. That there may be multiple sites of interaction with PS in the spectrin sequence has been inferred, but they have not hitherto been identified. Here we have explored the interaction of PS-containing liposomes with native alpha- and beta-spectrin chains and with recombinant spectrin fragments encompassing the entire sequences of both chains. We show that both alpha-spectrin and beta-spectrin bind PS and that sites of high affinity are located within 8 of the 38 triple-helical structural repeats which make up the bulk of both chains; these are alpha8, alpha9-10, beta2, beta3, beta4, beta12, beta13, and beta14, and PS affinity was also found in the nonhomologous N-terminal domain of the beta-chain. No other fragments of either chain showed appreciable binding. Binding of spectrin and its constituent chains to mixed liposomes of PS and phosphatidylcholine (PC) depended on the proportion of PS. Binding of spectrin dimers to PS liposomes was inhibited by single repeats containing PS binding sites. It is noteworthy that the PS binding sites in beta-spectrin are grouped in close proximity to the sites of attachment both of ankyrin and of 4.1R, the proteins engaged in attachment of spectrin to the membrane. We conjecture that direct interaction of spectrin with PS in the membrane may modulate its interactions with the proteins and that (considering also the known affinity of 4.1R for PS) the formation of PS-rich lipid domains, which have been observed in the red cell membrane, may be a result.