Effects of folding on metalloprotein active sites
Effects of folding on metalloprotein active sites
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DOI：
10.1073/pnas.94.9.4246
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发表时间：
1997-04-29
影响因子：
11.1
通讯作者：
Gray, HB
中科院分区：
文献类型：
--
作者：
Winkler, JR;WittungStafshede, P;Gray, HB
利用细胞色素c和天青素在氯化喹(GuHCl)作用下的去折叠实验数据，建立了氧化和还原蛋白质折叠的自由能图。对于细胞色素c，折叠还原蛋白的驱动力比折叠氧化形式的驱动力大。氧化和还原折叠形式的酵母细胞色素c的稳定性都不如马蛋白的相应状态。由于血红素的共价结合和固定的四方配位几何构型，细胞色素c的折叠可以用二态模型来描述。热力学循环导致了折叠和未折叠蛋白质的自交换重组能之差的表达式，折叠蛋白质中的电子交换重组能大约比水溶液中的血红素小0.5 eV。还原天青素在较低的GuHCl浓度下展开的发现表明，铜在氧化和还原未折叠状态下的配位结构不同：未折叠蛋白质中的铜-I的几何构型可能是线性或三角的，而铜-II更倾向于四方的。证据表明，与铜(1，10-邻菲咯啉)(2)(2+/+)参比体系相比，蛋白质折叠使天青重组能降低约1.7 eV。
Experimental data for the unfolding of cytochrome c and azurin by quanidinium chloride (GuHCl) are used to construct free-energy diagrams for the folding of the oxidized and reduced proteins. With cytochrome c, the driving force for folding the reduced protein is larger than that for the oxidized form. Both the oxidized and the reduced folded forms of yeast cytochrome c are less stable than the corresponding states of the horse protein. Due to the covalent attachment of the heme and is fixed tetragonal coordination geometry, cytochrome c folding can be described by a two-state model. A thermodynamic cycle leads to an expression for the difference in self-exchange reorganization energies for the folded and unfolded proteins, The reorganization energy for electron exchange in the folded protein is approximately 0.5 eV smaller than that for a heme in aqueous solution. The finding that reduced azurin unfolds at lower GuHCl concentrations than the oxidized protein suggests that the coordination structure of copper is different in oxidized and reduced unfolded states: it is likely that the geometry of Cu-I in the unfolded protein is linear or trigonal, whereas Cu-II prefers to be tetragonal. The evidence indicates that protein folding lowers the azurin reorganization energy by roughly 1.7 eV relative to an aqueous Cu(1,10-phenanthroline)(2)(2+/+) reference system.