HIGH-RESOLUTION CRYSTAL-STRUCTURE OF CYTOCHROME-P450CAM
HIGH-RESOLUTION CRYSTAL-STRUCTURE OF CYTOCHROME-P450CAM
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DOI：
10.1016/0022-2836(87)90190-2
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发表时间：
1987-06-05
影响因子：
5.6
通讯作者：
HOWARD, AJ
中科院分区：
文献类型：
--
作者：
POULOS, TL;FINZEL, BC;HOWARD, AJ
恶臭假单胞菌细胞色素P450cam与其底物樟脑结合的晶体结构已细化到R=0.19，正常分辨率为1.63。虽然1.63.ANG.模型证实了我们基于2.6ANG.模型的初步分析，但更高分辨率的结构揭示了重要的新细节。这些包括更精确的序列到二级结构的分配，三个顺式脯氨酸残基的鉴定，以及底物-蛋白质相互作用的更详细的图像。此外，还发现了204个有序的溶剂分子，其中一个似乎是阳离子。阳离子稳定了参与形成部分活性部位口袋的不利多肽构象，表明阳离子可能是金属离子结合部位，与众所周知的金属离子促进酶-底物复合体形成的能力有关。另一种不寻常的多肽构象形成了拟议的氧结合口袋。末端螺旋的局部扭曲和扩大为分子氧提供了一个口袋。侧链到主链氢键的复杂系统有助于稳定螺旋几何结构中所需的局部破坏。序列同源性强烈表明所有P450物种都有一个共同的氧结合口袋。P450物种之间的进一步序列比较表明，共同的三维结构与变化集中在分子的一个区域，推测与底物专一性的控制有关。
The crystal structure of Pseudomonas putida cytochrome P450cam with its substrate, camphor, bound has been refined to R = 0.19 at a normal resolution of 1.63 .ANG.. While the 1.63 .ANG. model confirms our initial analysis based on the 2.6 .ANG. model, the higher resolution structure has revealed important new details. These include a more precise assignment of sequence to secondary structure, the identification of three cis-proline residues, and a more detailed picture of substrate-protein interactions. In addition, 204 ordered solvent molecules have been found, one of which appears to be a cation. The cation stabilizes an iunfavorable polypeptide conformation involved in forming part of the active site pocket, suggesting that the cation may be the metal ion binding site associated with the well-known ability of metal ions to enhance formation of the enzyme-substrate complex. Another unusual polypeptide conformation forms the proposed oxygen-binding pocket. A localized distortion and widening of the distal helix provides a pocket for molecular oxygen. An intricate system of side-chain to backbone hydrogen bonds aids in stabilizing the required local disruption in helical geometry. Sequence homologies strongly suggest a common oxygen-binding pocket in all P450 species. Further sequence comparisons between P450 species indicate common three-dimensional structures with changes focused in a region of the molecule postulated to be associated with the control of substrate specificity.