Bongiovanni Cristiana, Sinibaldi Federica, Ferri Tommaso, Santucci Roberto
Università di Roma Tor Vergata, Dipartimento di Medicina Sperimentale e Scienze Biochimiche, Italy.
J Protein Chem. 2002 Jan;21(1):35-41. doi: 10.1023/a:1014179031881.
At high concentration (98% or higher, v/v), glycerol induces collapse of acid-denatured cytochrome c into a compact state, the G(U) state, showing a molten globule character. The G(U) state possesses a nativelike alpha-helix structure but a tertiary conformation less packed with respect to the native state. The spectroscopic properties of the G(U) state closely resemble those of the molten globule stabilized by the organic solvent from the native protein (called the G(N) state), indicating that glycerol can stabilize the molten globule of cytochrome c either from the native or the acid-denatured protein. The G(U) and the G(N) states show spectroscopic (and, thus, structural) properties and stabilities comparable to those of molten globules stabilized by different effectors, despite the fact that the mechanisms involved in the molten globule formation may significantly differ. This implies in cytochrome c a hierarchy for the rupture (native-to-molten globule) or the formation (unfolded-to-molten globule) of intramolecular interactions leading to the stabilization of the molten globule state of the protein, independently from the effector responsible for the structural transition, in accord with the sequential model proposed by Englander and collaborators.
在高浓度（98%或更高，v/v）下，甘油会诱导酸变性的细胞色素c塌陷成一种紧密状态，即G(U)状态，呈现出熔球特征。G(U)状态具有类似天然的α-螺旋结构，但相对于天然状态，其三级构象的堆积程度较低。G(U)状态的光谱性质与由天然蛋白质中的有机溶剂稳定的熔球（称为G(N)状态）的光谱性质非常相似，这表明甘油可以稳定细胞色素c从天然或酸变性蛋白质形成的熔球。尽管熔球形成所涉及的机制可能有显著差异，但G(U)和G(N)状态显示出与由不同效应剂稳定的熔球相当的光谱（以及结构）性质和稳定性。这意味着在细胞色素c中，分子内相互作用的断裂（天然态到熔球态）或形成（未折叠态到熔球态）存在一个层次结构，该层次结构导致蛋白质熔球态的稳定，而与负责结构转变的效应剂无关，这与Englander及其合作者提出的顺序模型一致。
