含有二硫键的蛋白质在6mol/L盐酸胍中变性后不是完全无序的

本文用紫外差光谱、紫外二阶导数光谱和圆二色光谱,对二硫键完整和经还原并氨酰羧甲基化(以下简称还原)的核糖核酸酶A(RNase A),牛血清白蛋白(BSA)和溶菌酶在6 mol/L盐酸胍中变性后的结构进行了比较。尽管在圆二色光谱中,二硫键完整和还原的变性蛋白都看不到α-螺旋和β-折叠等有序二级结构的存在,但是,与二硫键还原的变性蛋白相比,含有完整天然二硫键的变性蛋白在芳香族氨基酸残基侧链的暴露程度上明显较低。这些结果说明含有完整天然二硫键的蛋白在6mol/L盐酸胍中变性后可能仍然保留有一定程度的有序空间结构。     

二硫键完整对蛋白质在盐酸胍中变性时伸展的影响——Fourier红外光谱研究

利用Fourier红外光谱对二硫键完整和还原的核糖核酸酶A(RNase A),牛血清白蛋白(BSA)和溶菌酶在6mol/L盐酸胍中变性后的结构进行了比较。这三种蛋白质,在二硫键完整和还原状态下变性后的Fourier红外酰胺Ⅰ带光谱都表现了不同程度的差异,但是三种还原蛋白质在完全变性后的光谱却非常相似。说明含有完整天然二硫键的蛋白在6mol/L盐酸胍中变性后仍然有相当程度的残留有序结构,而二硫键断开的蛋白质完全变性后在结构上却是相似的。     

Effect of Native Disulfide Bonds on the Denaturation of Proteins in 6 mol/L Guanidinium Chloride——A Fourier Transformed Infrared Study

The unfolding of bovine serum albumin, lysozyme and ribonuclease A denatured in 6 mol/L GuHCl with their disulfide bridges intact and reduced have been compared by FTIR studies. The peak positions and heights in the deconvolved spectra of amide I bands of the above denatured proteins with native disulfide bonds show marked differences whereas those for the denatured proteins without disulfide linkages are closely similar. The above and other evidence suggest that denatured proteins with intact disulfides still have considerable ordered conformation even in 6 mol/L GuHCl.