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: 7026431
• 负责人: JAMES P COLLMAN
• 金额: $ 30.31万
• 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/7026431
• 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.

描述（由申请人提供）：呼吸，即细胞水平上分子氧的消耗，为代谢过程提供能量，由末端氧化酶如细胞色素c氧化酶（CcO）介导。最近的实验工作表明，CcO 调节能量产生的复杂性比迄今为止所认识的要复杂得多。一个具体因素是人们认识到一氧化氮 (NO)，一种气态自由基，在体内作为双氧与 CcO 结合的竞争性抑制剂具有重要作用。除了正常的（尽管知之甚少）NO 在体内的调节作用之外，这一重要的发现开启了这样的前景：相当多的病理状况是由 NO 的异常水平及其随后与蛋白质（例如电子传递链（其中 CcO 是末端元件）的蛋白质）的反应引起的。帕金森病、阿尔茨海默病、亨廷顿病和 ALS 都与 NO/CcO 配对有关。虽然有大量的现象学实验证明了能量调节和 NO 水平之间的联系，但 NO 的反应机制以及 CcO 血红素/铜活性位点中间体的物理化学特征，因为它们与调节和病理学相关，仍然存在争议。值得注意的是，CcO 的祖先一氧化氮还原酶 (NOR) 不会被 NO 抑制，而是将其还原为 N2O 并释放能量，这一反应类似于 CcO 将 O2 还原为 H2O。 NOR 还原 NO 的机制及其结构与此活性的关系鲜为人知。该项目继续以了解小分子在末端氧化酶活性位点的仿生反应为长期目标，旨在表征 NO 与血红素/铜 (CcO) 和血红素/铁 (NOR) 仿生复合物的反应。通过对先前开发的配体系统进行光谱和电化学研究，使用许多不可能通过生物学获得但对于分离体内酶学特征的因素至关重要的金属离子组合的双金属配合物，我们的目标是回答有关 NO 与 CcO 和 NOR 反应差异的许多问题。反应中间体的鉴定、它们的反应性、泄漏和可能的生物学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 的假定反应途径。