HIGH-RESOLUTION 3-DIMENSIONAL STRUCTURE OF HORSE HEART CYTOCHROME-C
HIGH-RESOLUTION 3-DIMENSIONAL STRUCTURE OF HORSE HEART CYTOCHROME-C
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DOI：
10.1016/0022-2836(90)90200-6
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发表时间：
1990-07-20
影响因子：
5.6
通讯作者：
BRAYER, GD
中科院分区：
文献类型：
--
作者：
BUSHNELL, GW;LOUIE, GV;BRAYER, GD
1.94 . ang。氧化马心脏细胞色素c的分辨率三维结构已被阐明并细化到最终r因子为0.17。这使得对这种蛋白质的结构特征进行了详细的评估，包括二级结构、氢键模式和血红素几何形状的存在。对马心脏细胞色素c与其他具有高分辨率结构的真核细胞色素c（酵母iso-1、金枪鱼、大米）之间结构差异的全面分析也已完成。这些蛋白质之间的显著构象差异发生在三个区域，主要涉及残基22至27、41至43和56至57。第一个可变区域是曲面的一部分。-环，而后两者位于一起毗邻血红素组。该研究还表明，在马细胞色素c中，Phe82的侧链以一种共面方式定位在血红素旁边，其构象与其他细胞色素c中的构象相似。因此，该残基的定位似乎与氧化状态无关。总共有5个水分子在马心脏、酵母iso-1、金枪鱼和水稻细胞色素c的结构中占据保守位置。其中3个位于蛋白质表面，用于稳定局部多肽链构象。其余两个位于内部。其中一种介导不变残基Arg38和附近的丙酸血红素之间的带电相互作用。另一个位于血红素铁原子的中心位置，与保守残基Asn52、Tyr67和Thr78形成氢键。如果比较不同来源的细胞色素c结构，则表明后一种水分子在氧化态变化时以一致的方式移动。这种结构特征的保存及其与血红素铁原子的密切关系强烈暗示这种内部水分子在细胞色素c的作用机制中具有功能作用。
The 1.94 .ANG. resolution three-dimensional structure of oxidized horse heart cytochrome c has heen elucidated and refined to a final R-factor of 0.17. This has allowed for a detailed assessment of the structural features of this protein, including the presence of secondary structure, hydrogen-bonding patterns and heme geometry. A comprehensive analysis of the structural differences between horse heart cytochrome c and those other eukaryotic cytochromes c for which high-resolution structures are available (yeast iso-1, tuna, rice) has also been completed. Significant conformational differences between these proteins occur in three regions and primarily involve residues 22 to 27, 41 to 43 and 56 to 57. The first of these variable regions is part of a surface .beta.-loop, whilst the latter two are located together adjacent to the heme group. This study also demonstrates that, in horse cytochrome c, the side-chain of Phe82 is positioned in a co-planar fashion next to the heme in a conformation comparable to that found in other cytochromes c. The positioning of this residue does not therefore appear to be oxidation-state-dependent. In total, five water molecules occupy conserved positions in the structures of horse heart, yeast iso-1, tuna and rice cytochromes c. Three of these are on the surface of the protein, serving to stabilize local polypeptide chain conformations. The remaining two are internally located. One of these mediates a charged interaction between the invariant residue Arg38 and a nearby heme propionate. The other is more centrally buried near the heme iron atom and is hydrogen bonded to the conserved residues Asn52, and Tyr67 and Thr78. It shown that this latter water molecule shifts in a consistent manner upon change in oxidation state if cytochrome c structures from various sources are compared. The conservation of this structural feature and its close proximity to the heme iron atom strongly implicate this internal water molecule as having a functional role in the mechanism of action of cytochrome c.