Baistrocchi P, Banci L, Bertini I, Turano P, Bren K L, Gray H B
Department of Chemistry, University of Florence, Italy.
Biochemistry. 1996 Oct 29;35(43):13788-96. doi: 10.1021/bi961110e.
Two-dimensional 1H NMR spectra of Saccharomyces cerevisiae reduced iso-1-cytochrome c have been used to confirm and slightly extend the assignment available in the literature. 1702 NOESY cross-peaks have been assigned, and their intensities have been measured. Through the program DIANA and related protocols (Güntert, 1992), a solution structure has been obtained by using 1442 meaningful NOEs and 13 hydrogen-bond constraints. The RMSD values with respect to the mean structure for the backbone and all heavy atoms for a family of 20 structures are 0.61 +/- 0.09 and 0.98 +/- 0.09 A, the average target function value being as small as 0.57 A2. The larger number of slowly exchanging amide NHs observed in this system compared to that observed in the cyanide derivative of oxidized Ala 80 cytochrome c suggests that the oxidized form is much more flexible and that the backbone protons are more solvent accessible. Comparison of the present structure with the crystal structures of reduced yeast cytochrome c and of the complex between cytochrome c peroxidase and oxidized yeast cytochrome c reveals substantial similarity among the backbone conformations but differences in the residues located in the region of protein-protein interaction. Interestingly, in solution the peripheral residues involved in the interaction with cytochrome c peroxidase are on average closer to the position found in the crystal structure of the complex than to the solid state structure of the isolated reduced from.
酿酒酵母还原型异-1-细胞色素c的二维¹H NMR谱已被用于确认并略微扩展文献中已有的归属。已归属了1702个NOESY交叉峰，并测量了它们的强度。通过DIANA程序及相关协议（Güntert，1992），利用1442个有意义的NOE和13个氢键约束获得了一个溶液结构。对于一组20个结构，其主链和所有重原子相对于平均结构的RMSD值分别为0.61±0.09 Å和0.98±0.09 Å，平均目标函数值小至0.57 Ų。与氧化型Ala 80细胞色素c的氰化物衍生物相比，该系统中观察到更多缓慢交换的酰胺NH，这表明氧化形式更加灵活，主链质子更容易与溶剂接触。将当前结构与还原型酵母细胞色素c的晶体结构以及细胞色素c过氧化物酶与氧化型酵母细胞色素c之间复合物的晶体结构进行比较，发现主链构象之间存在实质性相似性，但在蛋白质-蛋白质相互作用区域的残基存在差异。有趣的是，在溶液中，与细胞色素c过氧化物酶相互作用的外围残基平均而言更接近复合物晶体结构中发现的位置，而不是分离的还原型晶体结构中的位置。
