Structural features and the reaction mechanism of cytochrome oxidase: iron and copper X-ray absorption fine structure.
Structural features and the reaction mechanism of cytochrome oxidase: iron and copper X-ray absorption fine structure.
复制标题
细胞色素氧化酶的结构特点及反应机制：铁和铜X射线吸收精细结构。
DOI：
10.1016/s0006-3495(81)84863-1
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发表时间：
1981
影响因子：
3.4
通讯作者：
Angiolillo,P
中科院分区：
文献类型：
--
作者：
Powers,L;Chance,B;Ching,Y;Angiolillo,P
用X射线边缘吸收法研究了牛心、树枝状副球菌和HB-8嗜热菌的细胞色素氧化酶（血红素浓度为1-2.5 mM）的铜离子和铁离子的精细结构。X射线束中所需的氧化还原状态（完全氧化、还原的CO、混合价甲酸盐和CO）通过低温（~ 140 ℃）控制，并通过同时光谱法和通过每30分钟X射线暴露的电子顺磁共振（EPR）监测来连续监测。活性位点的结构，细胞色素a3-铜对在完全氧化和混合价甲酸盐状态，其中它们是自旋耦合，包含硫桥与三个配体2.60 +/- 0.03 A从Fea 3和2.18 +/- 0.03 A从Cua 3。Fea 3和Cua 3之间的距离为3.75 +/-0.05 A，使得硫键角103度对于sp3硫键合是合理的。Fea 3第一壳具有四个典型的血红素氮（2.01 +/- 0.03 A），其中近端氮在2.14 +/- 0.03 A。第六个配体是桥连硫。Cua 3的第一层壳与含有两个氮和一个桥硫的氧化的星花青苷相同。在用CO还原时，活性位点与Cua 3第一壳的还原星花青苷相同，并且含有在完全氧化和混合价甲酸盐状态下形成桥的硫。Fea 3第一壳与氧合血红蛋白相同，但具有CO而不是O2。其他氧化还原中心，Fea和其他“EPR可检测”的Cu没有观察到较高的外壳的Fea 3。Fea有六个等距的氮原子，Cua有一个（或两个）氮原子和三个（或两个）硫原子，这些配体在还原时只有轻微的变化。这些结构提供了基础的氧还原机制，涉及氧和过氧中间体。
X-ray edge absorption of copper and extended fine structure studies of both copper and iron centers have been made of cytochrome oxidase from beef heart, Paracoccus dentrificans, and HB-8 thermophilic bacteria (1–2.5 mM in heme). The desired redox state (fully oxidized, reduced CO, mixed valence formate and CO) in the x-ray beam was controlled by low temperature (-140 degrees C) and was continuously monitored by simultaneous optical spectroscopy and by electron paramagnetic resonance (EPR) monitoring every 30min of x-ray exposure. The structure of the active site, a cytochrome a3-copper pair in fully oxidized and in mixed valence formate states where they are spin coupled, contains a sulphur bridge with three ligands 2.60 +/- 0.03 A from Fea3 and 2.18 +/- 0.03 A from Cua3. The distance between Fea3 and Cua3 is 3.75 +/- 0.05 A, making the sulphur bond angle 103 degrees reasonable for sp3 sulphur bonding. The Fea3 first shell has four typical heme nitrogens (2.01 +/- 0.03 A) with a proximal nitrogen at 2.14 +/- 0.03 A. The sixth ligand is the bridging sulphur. The Cua3 first shell is identical to oxidized stellacyanin containing two nitrogens and a bridging sulphur. Upon reduction with CO, the active site is identical to reduced stellacyanin for the Cua3 first shell and contains the sulphur that forms the bridge in fully oxidized and mixed valence formate states. The Fea3 first shell is identical to oxyhemoglobin but has CO instead of O2. The other redox centers, Fea and the other "EPR detectable" Cu are not observed in higher shells of Fea3. Fea has six equidistant nitrogens and Cua has one (or two) nitrogens and three (or two) sulphurs with typical distances; these ligands change only slight on reduction. These structures afford the basis for an oxygen reduction mechanism involving oxy- and peroxy intermediates.