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Theoretical Study of Enzyme Reaction and DNA DamageMediated by Transition Metal Ion

过渡金属离子介导的酶反应与DNA损伤的理论研究

基本信息

批准号：
13440196
负责人：
YOSHIOKA Yasunori
金额：
$ 8.38万
依托单位：
Mie University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-13440196/
关键词：
Cytochrome c Oxidase Oxygen Reduction Proton Transfer Transition Metal Ion Hydrogen Bond DNA Damage Guanine Density Functional Method シトクロムC酸化酵素水素給合還元反応金属酵素遷移金属原子チトクロムc酸化酵素

项目摘要

1) Reduced cytochrome c oxidase (CcO) catalyses four-electron reduction of oxygen molecule to two water molecules. The reaction mechanism is not still conclusive, although experimentalists have proposed many different mechanisms. In this project, we have tried to study the mechanism of enzyme reaction by CcO, ad have completed study of mechanism yielding first water molecule from oxygen molecule. In summary, a) water exists between His290 and Tyr244 through hydrogen bonding. This water is a terminal molecule of network of hydrogen bonding connecting Tyr244, farnesylethyl, and Thr316, a terminal of K-channel. It is reasonable to think that a proton is transferred to this water molecule through the hydrogen-bonded network to yield the reduction of oxygen molecule. b) Hydronium ion formed by the proton transfer moves to molecular oxygen binding Fe atom of heme a3. After the proton is shifted to Fe-OO to give FeOOH, the water molecule goes back to the original position hydrogen-bonded to H … More is 290 and Tyr244. In other word, this water molecule plays an important role for proton deliver into reduction active site. c) An electron is transferred from Cu atom of CuB site to at the same time of an proton shift, yielding the change of electronic structure of Cu atom from monovalent to divalent. d) The activation energy of the proton transfer is estimated to be 12 kcal/mole under condition without molecular oxygen binding Fe atom. e) second proton necessary to form water molecule is also transferred by the water molecule hydrogen-bonding to His290 and Tyr244. f) Two electrons are transferred to the active site from heme a during the proton transfer, yielding the formation of the water molecule. In this project, we have completed the reduction mechanism of oxygen molecule catalyzed by fully reduce cytochrome c oxidase using the theoretical calculations of B3LYP method. Future project is to elucidate the mechanism yielding second water molecule.2) Experimental observation proposed that G_1 in 5'-XG_1G_2G_3-3' (X=T or C) is selectively damaged under condition of Cu-mediation. In this project, we investigated relative stabilities and electronic structures of the Cu-coordinated 5'-XG_1G_2G_3-3' and their cation radicals based on the structure of guanine coordinated by Cu(l) ion. we have concluded that the G_1-selectivity of GGG triplet is induced by the G_2-selective coordination of Cu(l) to 5'-XG_1G_2G_3-3'. Less

1)还原细胞色素c氧化酶（CcO）催化氧分子四电子还原为两个水分子。虽然实验学家提出了许多不同的反应机制，但反应机制仍然没有定论。在本项目中，我们尝试通过CcO对酶反应机理进行了研究，并完成了由氧分子生成第一水分子的机理研究。综上所述，a)在His290和Tyr244之间通过氢键存在水。该水是连接Tyr244、法尼乙基和Thr316的氢键网络的末端分子，是k通道的末端。我们有理由认为，一个质子通过氢键网络转移到这个水分子上，从而产生氧分子的还原。b)质子转移形成的水合氢离子移动到分子氧结合血红素a3的铁原子。当质子转移到Fe-OO生成FeOOH后，水分子回到原来的位置，与H…也就是说，这种水分子对质子传递到还原活性位点起着重要的作用。c)在质子移位的同时，Cu原子从CuB位转移了一个电子，使Cu原子的电子结构由一价变为二价。d)在没有分子氧结合铁原子的情况下，质子转移的活化能估计为12千卡/摩尔。e)形成水分子所需的第二个质子也通过水分子的氢键转移到His290和Tyr244上。f)在质子转移过程中，两个电子从血红素a转移到活性位点，形成水分子。在本项目中，我们利用B3LYP方法的理论计算完成了全还原细胞色素c氧化酶催化的氧分子还原机理。下一步的工作是进一步阐明生成第二水分子的机理。2)实验观察表明，5′-XG_1G_2G_3-3′（X=T或C）中的G_1在cu介导条件下发生选择性损伤。本课题基于Cu(l)离子配位的鸟嘌呤结构，研究了Cu配位的5′-XG_1G_2G_3-3′及其阳离子自由基的相对稳定性和电子结构。我们得出结论，GGG三重态的g_1选择性是由Cu(l)与5‘-XG_1G_2G_3-3’的g_1选择性配位引起的。少