FTIR Studies of Photosynthetic Oxygen Evolution

光合产氧的 FTIR 研究

• 批准号: 7018763
• 负责人: RICHARD J DEBUS
• 金额: $ 25.08万
• 依托单位: UNIVERSITY OF CALIFORNIA RIVERSIDE
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-07-03 至 2010-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7018763
• 关键词: Rhodospirillales; active sites; bacterial proteins; biochemical evolution; electron transport; infrared spectrometry; interferometry; ions; manganese; oxidation; oxygen; photosynthesis; photosynthetic reaction centers; photosystem; protein sequence; protein structure function; protonation; radiotracer; site directed mutagenesis; water

DESCRIPTION (provided by applicant): The project's overall goal is to elucidate the molecular mechanism of photosynthetic oxygen evolution. This process takes place in Photosystem II and is the source of nearly all atmospheric oxygen. The catalytic site contains a (Mn)4-Ca cluster that interacts with a redox-active tyrosine residue known as YZ. The YZ( radical extracts electrons and protons from the (Mn)4-Ca cluster, leading to the oxidation of water and the release of oxygen. The project's primary goal is to characterize the structural changes that accompany the oxidation of the (Mn)4-Ca cluster during the individual steps of the catalytic cycle. This information is crucial to understanding the mechanism of oxygen evolution and will complement the information that is being obtained from X-ray crystallography. The primary investigative tool will be Fourier transform infrared (FTIR) difference spectroscopy. The project's specific aims are: (1) To identify the specific Mn ion(s) that undergo oxidation during the individual steps in the catalytic cycle; (2) To identify the amino acid residues that serve as the critical bases that facilitate the proton-coupled oxidations of the (Mn)4-Ca cluster during the catalytic cycle; (3) To characterize the final intermediate of the oxygen formation reaction, an intermediate that can be trapped by increasing the ambient oxygen pressure; (4) To employ modified bacterial reaction centers as model systems for characterizing changes that occur in the environment of a ligated metal ion in response to its oxidation; (5) To employ near-infrared excitation resonance Raman spectroscopy as an additional tool for characterizing the environment of the (Mn)4-Ca cluster. In addition to providing fundamental insight into the mechanism of photosynthetic oxygen evolution, the project will provide insight into the mechanisms of metalloradical enzymes and enzymes whose mechanisms involve proton-coupled electron transfer (PCET) reactions. Such enzymes catalyze biological energy transduction in mitochondria. Elucidating the catalytic mechanisms of these enzymes is essential for understanding the molecular basis of mitochondrial diseases and aging. Photosystem II is both an excellent example of a metalloradical enzyme and a unique laboratory for studying proton-coupled electron transfer reactions. Its advantages derive from its ability to be stepped through its catalytic cycle with single flashes of light, thereby facilitating kinetic studies of reaction cycle intermediates with high time resolution.

描述（由申请人提供）：该项目的总体目标是阐明光合氧演化的分子机制。此过程发生在光系统II中，几乎是所有大气中的氧气的来源。催化位点包含一个（MN）4-Ca簇，该簇与称为Yz的氧化还原活性酪氨酸残基相互作用。 Yz（自由基提取物从（MN）4-Ca簇中的电子和质子导致水的氧化和氧气释放。该项目的主要目标是表征伴随（Mn）4-Ca群集氧化的结构变化，在催化周期中，该信息在催化周期中是至关重要的。该信息是从催化过程中进行的。晶体研究将是傅立叶变换的差异（FTIR）差异光谱。 （3）表征氧形成反应的最终中间体，该中间体可以通过增加环境氧气而捕获； （4）利用修饰的细菌反应中心作为模型系统，以表征在氧化后，在连接金属离子环境中发生的变化； （5）使用近红外激发共振拉曼光谱作为表征（MN）4-CA簇环境的附加工具。除了提供有关光合氧演化机制的基本洞察力外，该项目还将洞悉金属自由基酶和酶的机制，其机制涉及质子偶联电子转移（PCET）反应。这种酶催化线粒体中的生物能转导。阐明这些酶的催化机制对于理解线粒体疾病和衰老的分子基础至关重要。光系统II既是金银酶的一个很好的例子，也是研究质子耦合电子传递反应的独特实验室。它的优势源于单个光线闪烁的能力，从而在催化循环中逐步介入其催化循环，从而促进了与高时间分辨率的反应循环中间体的动力学研究。