Boffi F, Bonincontro A, Cinelli S, Congiu Castellano A, De Francesco A, Della Longa S, Girasole M, Onori G
Dipartimento di Fisica, Università "La Sapienza" Roma, INFM.
Biophys J. 2001 Mar;80(3):1473-9. doi: 10.1016/S0006-3495(01)76119-X.
We have studied, using x-ray absorption spectroscopy by synchrotron radiation, the native state of the horse heart cytochrome c (N), the HCl denatured state (U(1) at pH 2), the NaOH denatured state (U(2) at pH 12), the intermediate HCl induced state (A(1) at pH 0.5), and the intermediate NaCl induced state (A(2) at pH 2). Although many results concerning the native and denatured states of this protein have been published, a site-specific structure analysis of the denatured and intermediate solvent induced states has never been attempted before. Model systems and myoglobin in different states of coordination are compared with cytochrome c spectra to have insight into the protein site structure in our experimental conditions. New features are evidenced by our results: 1) x-ray absorption near edge structure (XANES) of the HCl intermediate state (A(1)) presents typical structures of a pentacoordinate Fe(III) system, and 2) local site structures of the two intermediate states (A(1) and A(2)) are different.
我们利用同步辐射X射线吸收光谱法研究了马心细胞色素c的天然状态（N）、HCl变性状态（pH 2时的U(1)）、NaOH变性状态（pH 12时的U(2)）、HCl诱导的中间状态（pH 0.5时的A(1)）以及NaCl诱导的中间状态（pH 2时的A(2)）。尽管已经发表了许多关于该蛋白质天然和变性状态的研究结果，但此前从未尝试过对变性和中间溶剂诱导状态进行位点特异性结构分析。将不同配位状态的模型系统和肌红蛋白与细胞色素c光谱进行比较，以便在我们的实验条件下深入了解蛋白质位点结构。我们的结果证明了一些新特征：1）HCl中间状态（A(1)）的X射线吸收近边结构（XANES）呈现出五配位Fe(III)系统的典型结构，2）两种中间状态（A(1)和A(2)）的局部位点结构不同。
