Edwin F, Jagannadham M V
Molecular Biology Unit, Institute of Medical Sciences, Banaras Hindu University, Varanasi, 221 005, India.
Biochem Biophys Res Commun. 1998 Nov 27;252(3):654-60. doi: 10.1006/bbrc.1998.9720.
Papain exhibits the characteristics of molten globule under acidic conditions as seen by circular dichroism, fluorescence and ANS binding. Between pH 2.0-2.5 the protein exhibits substantial secondary structure as indicated by far-UV CD spectrum but loses the persistent tertiary interactions of the native state. Enhanced binding of ANS to the state at pH 2.0 in relation to the native and unfolded states at neutral pH indicates a considerable exposure of aromatic side chains. Temperature and guanidine hydrochloride induced unfolding of papain in this state is noncooperative and the transition curves are biphasic in nature. As papain molecule consists of two domains, the results suggest that the domains unfold independently and sequentially.
通过圆二色性、荧光和ANS结合可以看出，木瓜蛋白酶在酸性条件下呈现出熔球态的特征。在pH 2.0 - 2.5之间，远紫外CD光谱表明该蛋白质具有大量二级结构，但失去了天然状态下持久的三级相互作用。与中性pH下的天然态和未折叠态相比，ANS在pH 2.0时与该状态的结合增强，表明芳香族侧链大量暴露。在这种状态下，温度和盐酸胍诱导的木瓜蛋白酶去折叠是非协同的，转变曲线本质上是双相的。由于木瓜蛋白酶分子由两个结构域组成，结果表明这些结构域是独立且依次展开的。
