摘要
在酸性条件下用硫酸银断裂马心细胞色素ｃ（以下简称ｃｙｔ．ｃ）的肽链与血红素相连的硫醚键，通过酸性丙酮抽提，硫基乙醇处理及超速离心等步骤纯化得去血红素的ｃｙｔ．ｃ（以下简称Ａｐｏ－ｃｙｔ．ｃ）。Ａｐｏ－ｃｙｔ．ｃ与天然ｃｙｔ．ｃ相比，其酸性电泳迁移率明显降低，紫外－可见光谱在１９０～２２０ｎｍ处吸收上升，荧光光谱的最大发射峰波长产生红移，同时ＣＤ谱中α螺旋的特征峰完全消失，这说明在ｃｙｔ．ｃ去血红素的过程中，蛋白质已由原来的紧密球状结构变成了较为松散、伸展的无规卷曲构象。因此，血红素对ｃｙｔ．ｃ天然构象的维持有着重要作用。
The two thioether bonds which link the heme moiety with polypeptide chain of horse heart cytochrome c were cleaved by reaction with silver sulfate in acidic solution. The pure apoprotein was obtained after being extracted with acid acetone,treated with 2-mercaptoethanol and ultracentrifuged. Compared with native cytochrome c, Apo-cyt.c moved slower in acidic electrophoresis. However, the absorbance in ultra-visible spectrum was raised between 190 nm and 220 nm, and the maximum emission wavelength exhibited an apparant red-shifted. In the CD spectrum,the specific absorbance of α-helix was disappeared completely. all these results suggested that the compact and nearly spherical comformatiom of native cytochrome c was distroyed to a randomly coiled comformation when the heme moiety was removed from the protein.Therefore,it can be concluded that the heme moiety is necessary for cyt. c to stabilize its native comformation.
基金
国家自然科学基金
