OXYGEN ACTIVATION BY NON HEME FE PROTEINS

非血红素铁蛋白的氧激活

• 批准号: 2770980
• 负责人: Boi-Hanh V. Huynh
• 金额: $ 16.92万
• 依托单位: EMORY UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-09-30 至 2000-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2770980
• 关键词: Escherichia coli; Mossbauer spectrometry; bacterial proteins; cofactor; electron spin resonance spectroscopy; enzyme mechanism; ferritin; ferroxidase; iron sulfur protein; metal complex; methane monooxygenase; oxidation reduction reaction; oxygen; protein structure function; ribonucleotide reductase

DESCRIPTION: Reactions of the oxygen molecule with organic compounds are energetically favorable and constitute some of the most important energy-yielding metabolic processes in biology. The reactions are kinetically stable, however, due to the fact that the ground state of dioxygen is a triplet state and the reactions are therefore spin forbidden. This kinetic stability has prevented the abundant oxygen on earth from reacting uncontrollably with organic materials and has made life on earth possible. Hence, to understand how nature overcomes this kinetic barrier and controls the dioxygen reactivities is of fundamental and vital importance. In biology, activation of dioxygen is generally achieved by complexing the oxygen molecule with metal cofactors in proteins. Up until now, the best known and most studied protein systems that catalyze O2-dependent reactions are probably the heme-containing proteins. More recently, however, it has become obvious that proteins containing carboxylate-bridged diiron centers represent yet another group of proteins that possesses catalytic capabilities as diverse as those of hemoproteins. For the past few years, we have applied optical, Mossbauer and EPR spectroscopies to characterize the carboxylate-bridged diiron centers in the wild-type and recombinant rubrerythrin. We have also used the rapid freeze-quench Mussbauer and EPR methods to study (a) the reconstitution of the diiron-tyrosyl radical cofactor in the R2 subunit of the ribonucleotide reductase (RNR) from Escherichia coli, and (b) the reaction of O2 with the diferrous center in methane monooxygenase (MMO) from Methylococus capsulatus (Bath). Several novel, kinetically competent, transient intermediates have been identified and partially characterized. In this application, we request support to continue our kinetic and spectroscopic investigations on rubrerythrin, RNR, and MMO, and to extend our research program to include mechanistic studies on the ferroxidase activity of ferritin. Recent studies in ferritin suggest that a carboxylate-bridged diiron center may be involved in the Fe(II) oxidation during the initial stage of the ferrihydrite core formation. Our specific objective is to obtain mechanistic information on the reaction of the ferrous centers with O2 in these protein systems. Our general goal is to understand how biology uses protein structure to control the reactivity of complex metal centers, in this case, controlling the carboxylate-bridged diiron center to activate O2 for a variety of catalytic functions.

描述：氧分子与有机化合物的反应是 在精力上有利，并构成了一些最重要的 生物学中产生能量的新陈代谢过程。他们的反应是 然而，动力学稳定，因为基态是 氧是三重态，因此反应是自旋禁止的。 这种运动稳定性阻止了地球上丰富的氧气 无法控制地与有机物质反应，并使地球上的生命 有可能。因此，要了解自然界是如何克服这种动力学障碍的 和控制氧气的反应性是根本和至关重要的 重要性。在生物学中，氧气的活化通常是通过 使氧分子与蛋白质中的金属辅因子络合。一直到 现在，最广为人知和研究最多的蛋白质体系 O2依赖的反应可能是含血红素的蛋白质。更多 然而，最近已经变得明显的是，含有 羧酸桥联的双铁中心代表了另一类蛋白质 具有与血红素蛋白一样多样的催化能力。 在过去的几年里，我们应用了光学、穆斯堡尔和电子顺磁共振 用光谱分析方法表征羧酸桥联的双铁中心 野生型和重组红蛋白。我们还使用了快速 冷冻-淬火Mussbauer和EPR方法研究(A)重建 核糖核酸R2亚基中的二铁-酪氨酸基辅助因子 (B)氧与细菌的反应。 荚膜甲氧球菌产甲烷单加氧酶(MMO)的二亚铁中心 (巴斯)。几种新颖的、具有运动能力的瞬时中间体 已被识别并部分表征。在此应用程序中，我们 请求支持以继续我们的动力学和光谱研究 RNR和MMO，并将我们的研究计划扩展到包括 铁蛋白铁氧合酶活性的机理研究。最新研究 在铁蛋白中，提示可能与羧酸桥联的双铁中心有关 在铁水合石芯初始阶段的Fe(II)氧化 队形。我们的具体目标是获取关于 在这些蛋白质体系中，铁中心与O2的反应。我们的 总的目标是了解生物学如何利用蛋白质结构来控制 复杂金属中心的反应性，在这种情况下，控制着 羧酸桥联二铁中心活化O2的各种催化作用 功能。