膜脂质微环境改变对CD71蛋白分子结构的影响

Effects of changes of membrane lipid microenvironment on CD71 protein conformation

采用亲和层析法从人胎盘滋养层细胞和Ｍｏｌｔ－４细胞分离到高纯度ＣＤ７１蛋白，ＳＤＳ－ＰＡＧＥ显示，在还原条件下有一明显９０×１０３ｕ蛋白带。将此蛋白分子重组到由不同磷脂、胆固醇（Ｃｈ）构成的人工脂双层膜上，圆二色谱分析表明，随ＤＭＰＣ／Ｃｈ和ＤＯＰＣ／Ｃｈ脂膜上胆固醇增加，ＣＤ７１蛋白β－片层结构减少，而α－螺旋及无规卷曲结构增多，色氨酸荧光光谱扫描也提示，随人工脂膜上脂质组成的变化。

Highly purified CD71 protein was isolated from human placental trophoblasts and Molt 4 cells with affinity chromatography. SDS PAGE revealed that it was a single major species with an apparent mass of 90×10 3 u under reducing condition. After the protein was reconstituted into the artificial membrane composed of various phospholipids and cholesterol (Ch), circular dichroism measurements indicated that CD71 underwent a conformational change from b structure to a helica and random coil upon interaction with the increment of Ch content in DMPC/Ch or DOPC/Ch artificial membrane. Meanwhile, tryptophan fluorescence spectra also indicated that the conformation of CD71 protein was changed with the modification of lipid composition in artificial membrane.