Uversky V N, Ptitsyn O B
Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region, Russia.
Fold Des. 1996;1(2):117-22. doi: 10.1016/S1359-0278(96)00020-X.
It has long been established that temperature-induced melting of small globular proteins is an all-or-none transition. Little was known, however, about the degree of cooperativity of denaturant-induced transitions in proteins, especially in those cases in which the proteins unfold through the molten globule state.
We have processed data on the equilibrium urea-induced and guanidinium chloride (GdmCl)-induced unfolding of globular proteins from the native to the unfolded state, from the native to the molten globule state and from the molten globule to the unfolded state. We show that in all these cases, the cooperativity of unfolding increases linearly with the increase of the molecular weight of the protein up to 25-30 kDa.
The cooperative unit of the urea-induced and GdmCl-induced equilibrium transitions of small proteins between the native, molten globule and unfolded states includes the protein molecule as a whole. In other words, both native and molten globule proteins are unfolded by strong denaturing solvents according to an all-or-none mechanism.
长期以来人们已经确定，温度诱导的小球状蛋白质解链是一种全或无的转变。然而，对于变性剂诱导的蛋白质转变的协同程度，尤其是在蛋白质通过熔球态展开的情况下，人们了解甚少。
我们处理了有关球状蛋白质在平衡状态下由尿素和氯化胍（GdmCl）诱导从天然态到未折叠态、从天然态到熔球态以及从熔球态到未折叠态展开的数据。我们表明，在所有这些情况下，直至25 - 30 kDa，展开的协同性随蛋白质分子量的增加而线性增加。
小分子蛋白质在天然态、熔球态和未折叠态之间由尿素和GdmCl诱导的平衡转变的协同单元包括整个蛋白质分子。换句话说，天然态和熔球态蛋白质在强变性溶剂作用下均按照全或无机制展开。
