Biomimetic Studies of NO-binding Respiratory Chain Hemes

NO 结合呼吸链血红素的仿生研究

• 批准号: 6866034
• 负责人: JAMES P COLLMAN
• 金额: $ 31.04万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-04-01 至 2009-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6866034
• 关键词: Alzheimer' s disease; Huntington' s disease; Parkinson' s disease; active sites; biomimetics; cellular respiration; copper; cytochrome oxidase; electrochemistry; electron transport; heme; ligands; nitric oxide; oxidoreductase; spectrometry

DESCRIPTION (provided by applicant): Respiration, the consumption of dioxygen at the cellular level to provide energy for metabolic processes, is mediated by terminal oxidases such as cytochrome c oxidase (CcO). Recent experimental work has revealed more complexity in the regulation of energy production by CcO than hitherto appreciated. One specific factor has been the realization that nitric oxide (NO), a gaseous free radical, has an important role in vivo as a competitive inhibitor of dioxygen binding to CcO. Aside from the normal, although poorly understood, regulatory role of NO in vivo this important discovery opened the prospect that a considerable number of pathological conditions arise from abnormal levels of NO and its subsequent reactions with proteins such as those of the electron transport chain (of which CcO is terminal element). Parkinson's, Alzheimer's, Huntington's disease and ALS have been linked to the NO/CcO couple. While there are a plethora of phenomenological experiments demonstrating the connection between energy regulation and NO levels, the mechanism of reaction of NO and the physicochemical characteristics of intermediates at the heme/copper active site of CcO as they relate to regulation and pathology remain controversial. Significantly, an ancestral progenitor of CcO, Nitric Oxide Reductase (NOR), is not inhibited by NO, but reduces it to N20 with release of energy, a reaction analogous to the reduction of O2 to H2O by CcO. The mechanism by which NOR reduces NO and the relationship of its structure to this activity is little known. Continuing a long-term goal of understanding biomimetic reactions of small molecules at the active sites of terminal oxidases, this project aims to characterize the reaction of NO with heme/copper (CcO) and heme/iron (NOR) biomimetic complexes. Through spectroscopic and electrochemical investigation of previously-developed ligand systems, using numerous bimetallic complexes with metal ion combinations not possible to obtain biologically, but essential for isolating the factors that are contributing to the enzymatic characteristics in vivo, we aim to answer many questions concerning the differences in NO reaction with CcO and NOR. The identification of reaction intermediates, their reactivity, leakage and possible biological consequences will be a focus for study. An emphasis will be placed on kinetic and mechanistic studies to elucidate the putitive reaction pathways of CcO and NOR.

说明(申请人提供)：呼吸作用，即在细胞水平上消耗氧气为新陈代谢过程提供能量，是由细胞色素C氧化酶(CcO)等末端氧化酶调节的。最近的实验工作揭示了CCOO对能源生产的调控比迄今所认为的更加复杂。一个特殊的因素是认识到一氧化氮(NO)是一种气体自由基，在体内作为氧与CcO结合的竞争性抑制物具有重要作用。除了正常的、尽管知之甚少的NO在体内的调节作用外，这一重要的发现开启了一种前景，即相当多的病理状况是由NO水平异常及其随后与蛋白质的反应引起的，例如电子传递链(CcO是末端元件)。帕金森氏症、阿尔茨海默氏症、亨廷顿氏症和肌萎缩侧索硬化症都与这对NO/CcO夫妇有关。虽然有大量的现象学实验证明了能量调节与NO水平之间的联系，但NO的反应机制以及与调节和病理相关的中间体在CcO的血红素/铜活性中心的物理化学特征仍然存在争议。值得注意的是，一氧化碳的祖先一氧化氮还原酶(NOR)不被NO抑制，而是随着能量的释放将其还原为N20，这一反应类似于CcO将O2还原为H2O。NOR还原NO的机制及其结构与这一活性的关系鲜为人知。该项目继续了解小分子在末端氧化酶活性部位的仿生反应这一长期目标，旨在表征NO与血红素/铜(CcO)和血红素/铁(NOR)仿生络合物的反应。通过对以前开发的配体系统的光谱和电化学研究，使用许多双金属配合物与金属离子结合，这是生物上不可能获得的，但对于分离影响体内酶特性的因素是必不可少的，我们的目标是回答许多关于NO与CcO和NOR反应的差异的问题。反应中间体的鉴定、它们的反应性、泄漏和可能的生物后果将是研究的重点。重点将放在动力学和机理研究上，以阐明CcO和NOR的催化反应途径。