STRUCTURES OF METAL SITES OF OXIDIZED BOVINE HEART CYTOCHROME-C-OXIDASE AT 2.8 ANGSTROM
STRUCTURES OF METAL SITES OF OXIDIZED BOVINE HEART CYTOCHROME-C-OXIDASE AT 2.8 ANGSTROM
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DOI：
10.1126/science.7652554
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发表时间：
1995-08-25
期刊：
影响因子：
56.9
通讯作者：
YOSHIKAWA, S
中科院分区：
文献类型：
--
作者：
TSUKIHARA, T;AOYAMA, H;YOSHIKAWA, S
本文报道了牛心细胞色素c氧化酶金属位点的高分辨三维x射线结构。细胞色素c氧化酶是迄今为止最大的膜蛋白质结晶和原子分辨率分析。氧化的牛细胞色素c氧化酶在2.8埃分辨率下的电子密度分布表明双核铜中心具有与[2Fe-2S]型铁硫中心类似的意想不到的结构。先前预测的锌和镁位点已经被定位，前者由膜基质侧的核编码亚基结合，后者位于血红素a（3）和Cu-A之间，在亚基I和II的界面处。O-2结合位点含有血红素a（3）铁和铜原子（Cu-B），原子间距离为4.5埃;尽管铁和铜原子之间存在强反铁磁耦合，但在铁和铜原子之间没有可检测到的桥接配体。血红素a（3）的羟基法呢基乙基侧链的羟基与酪氨酸的OH之间存在氢键。酪氨酸酚平面是直接相邻和垂直的咪唑基团键合到铜-B，这表明在分子内电子转移或构象控制，后者可能会引起的氧化还原耦合质子泵的可能作用。位于血红素a（3）的吡咯平面和与另一个家庭（血红素a）配位的咪唑平面之间的苯基也可以影响电子转移或构象控制。
The high resolution three-dimensional x-ray structure of the metal sites of bovine heart cytochrome c oxidase is reported. Cytochrome c oxidase is the largest membrane protein yet crystallized and analyzed at atomic resolution. Electron density distribution of the oxidized bovine cytochrome c oxidase at 2.8 Angstrom resolution indicates a dinuclear copper center with an unexpected structure similar to a [2Fe-2S]-type iron-sulfur center. Previously predicted zinc and magnesium sites have been located, the former bound by a nuclear encoded subunit on the matrix side of the membrane, and the latter situated between heme a(3) and Cu-A, at the interface of subunits I and II. The O-2 binding site contains heme a(3) iron and copper atoms (Cu-B) with an interatomic distance of 4.5 Angstrom; there is no detectable bridging ligand between iron and copper atoms in spite of a strong antiferromagnetic coupling between them. A hydrogen bond is present between a hydroxyl group of the hydroxyfarnesylethyl side chain of heme a(3) and an OH of a tyrosine. The tyrosine phenol plane is immediately adjacent and perpendicular to an imidazole group bonded to Cu-B, suggesting a possible role in intramolecular electron transfer or conformational control, the latter of which could induce the redox-coupled proton pumping. A phenyl group located halfway between a pyrrole plane of the heme a(3) and an imidazole plane liganded to the other home (heme a) could also influence electron transfer or conformational control.