Structures of recombinant human and mouse NAD(P)H:quinone oxidoreductases:: Species comparison and structural changes with substrate binding and release
Structures of recombinant human and mouse NAD(P)H:quinone oxidoreductases:: Species comparison and structural changes with substrate binding and release
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DOI：
10.1073/pnas.050585797
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发表时间：
2000-03-28
影响因子：
11.1
通讯作者：
Amzel, LM
中科院分区：
文献类型：
--
作者：
Faig, M;Bianchet, MA;Amzel, LM
NAD（P）H/醌受体氧化还原酶（QR 1，NQO 1，以前称为DT-心肌黄酶; EC 1.6.99.2）保护动物细胞免受醌类和其他亲电体的有害和致癌作用。在本文中，我们报告的apoenzyme结构的人（在1.7埃分辨率）和小鼠（2.8埃）的QR 1和复合物的人酶与底物duroquinone（2.5埃）（2，3，5，6-四甲基对苯醌）。除了提供几个物种之间的结构和催化差异的描述和理由外，这些结构还揭示了伴随底物或辅因子（NAD）结合和释放的变化。酪氨酸-128和跨越残基232-236的环关闭结合位点，部分占据离开分子（底物或辅因子）留下的空位。这些变化突出了乒乓机制所需的对进入催化位点的精确控制，其中在还原黄素后，NAD（P）（+）离开催化位点并允许底物结合在空出的位置。在人的QR 1-杜醌结构中，一个环碳明显更接近黄素N5，表明氢化物直接转移到这个原子。
NAD(P)H/quinone acceptor oxidoreductase (QR1, NQO1, formerly DT-diaphorase; EC 1.6.99.2) protects animal cells from the deleterious and carcinogenic effects of quinones and other electrophiles. In this paper we report the apoenzyme structures of human (at 1.7-Angstrom resolution) and mouse (2.8 Angstrom) QR1 and the complex of the human enzyme with the substrate duroquinone (2.5 Angstrom) (2,3,5,6-tetramethyl-p-benzoquinone). In addition to providing a description and rationale of the structural and catalytic differences among several species, these structures reveal the changes that accompany substrate or cofactor (NAD) binding and release. Tyrosine-128 and the loop spanning residues 232-236 close the binding site, partially occupying the space left vacant by the departing molecule (substrate or cofactor). These changes highlight the exquisite control of access to the catalytic site that is required by the ping-pong mechanism in which, after reducing the flavin, NAD(P)(+) leaves the catalytic site and allows substrate to bind at the vacated position. In the human QR1-duroquinone structure one ring carbon is significantly closer to the flavin N5, suggesting a direct hydride transfer to this atom.