Di Primo C, Deprez E, Hoa G H, Douzou P
INSERM-INRA U310, Institut de Biologie Physico-Chimique, Paris, France.
Biophys J. 1995 May;68(5):2056-61. doi: 10.1016/S0006-3495(95)80384-X.
The combined effects of hydrostatic pressure and osmotic pressure, generated by polyols, on the spin equilibrium of fenchone-bound cytochrome P-450cam were investigated. Hydrostatic pressure indices a high spin to low spin transition, whereas polyols induce the reversed reaction. Of the four solutes used, glycerol, glucose, stachyose, and sucrose, only the last two would act on the spin transition by osmotic stress. The spin volume changes measured by both techniques are different, 29 and -350 ml/mol for hydrostatic pressure and osmotic pressure, respectively. It suggests that even if the two are perturbing water molecules, different properties are probed. From the volume change induced by osmotic stress, 19 water molecules are deduced that would be implicated in the spin transition of the fenchone-bound protein. This result suggests that water molecules other than the well defined ones located in the active site play a key role in modulating the spin equilibrium of cytochrome P-450cam.
研究了多元醇产生的静水压力和渗透压对小茴香酮结合的细胞色素P-450cam自旋平衡的综合影响。静水压力促使高自旋向低自旋转变，而多元醇则引发相反的反应。在所使用的四种溶质甘油、葡萄糖、水苏糖和蔗糖中，只有后两种会通过渗透压作用于自旋转变。两种技术测得的自旋体积变化不同，静水压力和渗透压分别为29和-350毫升/摩尔。这表明，即使两者都在扰动水分子，但探测的是不同的性质。根据渗透压引起的体积变化，推断出19个水分子与小茴香酮结合蛋白的自旋转变有关。这一结果表明，位于活性位点之外的水分子在调节细胞色素P-450cam的自旋平衡中起关键作用。
