Williams G, Clayden N J, Moore G R, Williams R J
J Mol Biol. 1985 Jun 5;183(3):447-60. doi: 10.1016/0022-2836(85)90013-0.
The two accompanying papers describe the assignment of methyl-containing spin-systems in the 1H nuclear magnetic resonance spectra of tuna ferricytochrome c and tuna ferrocytochrome c. At present, 104 resonances from 208 C-H protons are assigned in both oxidation states. In this paper, the difference in chemical shift of a resonance between the two oxidation states is used together with a dipolar model of the unpaired electron spin of ferricytochrome c to compare the structure of cytochrome c in solution with three high-resolution structures of cytochrome c obtained by X-ray diffraction in single crystals. The overall protein fold and the positions of most of the haem-packing residues are shown to be invariant between the crystal and solution. However, three regions of the protein, at the C terminus, around the haem propionic acid groups and at the haem crevice near thioether-2, are found to undergo conformational changes on the removal of crystal packing constraints.
随附的两篇论文描述了金枪鱼高铁细胞色素c和金枪鱼亚铁细胞色素c的1H核磁共振谱中含甲基自旋系统的归属。目前，在两种氧化态下已归属了来自208个C-H质子的104个共振峰。在本文中，利用两种氧化态之间共振峰化学位移的差异，结合高铁细胞色素c未成对电子自旋的偶极模型，将溶液中细胞色素c的结构与通过X射线衍射在单晶中获得的细胞色素c的三种高分辨率结构进行比较。结果表明，晶体和溶液中蛋白质的整体折叠以及大多数血红素堆积残基的位置是不变的。然而，发现蛋白质的三个区域，即C末端、血红素丙酸基团周围以及硫醚-2附近的血红素裂隙处，在去除晶体堆积限制后会发生构象变化。
