Identification and functional characterization of protein 4.1R and actin-binding sites in erythrocyte β spectrin:: Regulation of the interactions by phosphatidylinositol-4,5-bisphosphate
Identification and functional characterization of protein 4.1R and actin-binding sites in erythrocyte β spectrin:: Regulation of the interactions by phosphatidylinositol-4,5-bisphosphate
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DOI：
10.1021/bi047331z
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发表时间：
2005-08-09
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;Debnath, G;Mohandas, N
血影蛋白、F-肌动蛋白和蛋白质4.1R的三元复合物定义了红细胞膜骨架网络，其控制膜的稳定性和弹性。研究表明，4.1R和肌动蛋白均与血影蛋白β链的N-末端区域（残基1-301）结合，该区域含有两个钙调蛋白同源结构域，命名为CH 1和CH 2。在这里，我们表明，4.1R也结合到单独的CH 1和CH 2结构域。出乎意料的是，通过其20个氨基酸截短CH 2结构域，对应于其N-末端α螺旋，发现大大增强了其与4.1R的结合。完整的N末端和CH 1而不是CH 2结构域与F-肌动蛋白结合，但同样，后者的前20个氨基酸的缺失暴露了肌动蛋白结合活性。如预期的，多肽1-301在体外抑制血影蛋白二聚体与肌动蛋白的结合以及血影蛋白-肌动蛋白-4.1R三元复合物的形成。此外，PIP 2极大地增强了4.1R与1-301的结合，这意味着细胞中存在调节开关。
The ternary complex of spectrin, F-actin, and protein 4.1R defines the erythrocyte membrane skeletal network, which governs the stability and elasticity of the membrane. It has been shown that both 4.1R and actin bind to the N-terminal region (residues 1-301) of the spectrin beta chain, which contains two calponin homology domains, designated CH1 and CH2. Here, we show that 4.1R also binds to the separate CH1 and CH2 domains. Unexpectedly, truncation of the CH2 domain by its 20 amino acids, corresponding to its N-terminal a helix, was found to greatly enhance its binding to 4.1R. The intact N terminus and the CH1 but not the CH2 domain bind to F-actin, but again, deletion of the first 20 amino acids of the latter exposes an actin-binding activity. As expected, the polypeptide 1-301 inhibits the binding of spectrin dimer to actin and formation of the spectrin-actin-4.1R ternary complex in vitro. Furthermore, the binding of 4.1R to 1-301 is greatly enhanced by PIP2, implying the existence of a regulatory switch in the cell.