MANGANESE OXYGEN-EVOLVING COMPLEX: STRUCTURE/FUNCTION

锰放氧络合物：结构/功能

• 批准号: 6952585
• 负责人: VITTAL YACHANDRA
• 金额: $ 10.3万
• 依托单位: UNIVERSITY OF CALIF-LAWRENC BERKELEY LAB
• 依托单位国家: 美国
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-01-01 至 2005-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6952585
• 关键词: X ray spectrometry; bromine; calcium ion; chemical models; chemical structure function; chloride ion; cofactor; conformation; electron spin resonance spectroscopy; enzyme mechanism; enzyme structure; intermolecular interaction; ligands; manganese; metalloenzyme; molecular shape; molecular site; oxidation reduction reaction; oxygen; photosystem; strontium; structural biology; water

DESCRIPTION: (Adapted from applicant's abstract) Metalloproteins containing Mn in a redox active role are involved in a variety of physiologically important reactions involving dioxygen metabolism. These include, amongst others, a superoxide dismutase that detoxifies superoxide radicals to O(2) and peroxide, a catalase that disproportionates peroxide to O(2) and H(2)O, a ribonucleotide reductase that catalyzes synthesis of deoxyribonucleotide, and perhaps the most complex and important, the Mn-containing oxygen-evolving complex (Mn-OEC) that is involved in the oxidation of water to dioxygen in Photosystem II. Oxygen, which supports all aerobic life, is abundant in the atmosphere because of its constant regeneration by photosynthetic water oxidation by the Mn-OEC. The light-induced oxidation of water to dioxygen is one of the most important chemical process4es occurring on such a large scale in the biosphere. Photosynthetic water oxidation involves removal of four electrons, in a stepwise manner by light-induced oxidation, from two water molecules by the Mn-OEC to produce a molecule of oxygen. Central questions that need to be resolved and the overall objective of this proposal are as follows: 1) Determine the oxidation states of Mn in the four intermediate or S-states, 2) Characterize the structural changes of the oxo-bridged tetranuclear Mn complex as it advances through the enzymatic cycle, 3) Determine the mechanism of water oxidation and oxygen evolution, 4) Elucidate the structural and functional role of the essential cofactors C1(-) and Ca(2+). The interplay between X-ray absorption spectroscopy (XAS) and Electron paramagnetic resonance (EPR) has played an essential role in our understanding of the structural and mechanistic aspects of O(2) evolution. The oxidation states of Mn and the structural changes of the Mn complex as it advances through the enzymatic cycle are determined by X-ray absorption spectroscopy using samples characterized by EPR spectroscopy. The oxidation states are determined by Mn K- and L-edge spectroscopy, and high resolution X-ray fluorescence spectroscopy. The structure of the intermediates are characterized by XAS using samples prepared by flash illumination. The role of cofactors Ca(2+) and C1(-) Br(-) is addressed by Ca (Sr) and C1 (Br) K-edge XAS respectively.

描述：（改编自申请人的摘要）含锰金属蛋白 具有氧化还原活性，参与多种重要的生理功能 涉及双氧代谢的反应。其中包括，除其他外， 超氧化物歧化酶将超氧自由基解毒为 O(2) 和过氧化物， 一种过氧化氢酶，可将过氧化物歧化为 O(2) 和 H(2)O（一种核糖核苷酸） 催化脱氧核糖核苷酸合成的还原酶，也许是最重要的 复杂而重要的是，含锰析氧络合物（Mn-OEC） 参与光系统 II 中水氧化成分子氧的过程。 大气中氧气含量丰富，是所有有氧生命的基础 Mn-OEC 通过光合水氧化不断再生。 光诱导水氧化成双氧是最重要的氧化反应之一 生物圈中发生如此大规模的化学过程。 光合水氧化涉及去除四个电子， 通过光诱导氧化，由两个水分子逐步进行 Mn-OEC 产生氧分子。需要解决的核心问题 解决方案及本提案的总体目标如下： 1) 确定 Mn 的四种中间态或 S 态的氧化态，2) 表征氧桥四核锰络合物的结构变化 随着酶循环的进展，3) 确定水的机制 氧化和析氧，4）阐明结构和功能作用 必需辅因子 C1(-) 和 Ca(2+)。 X 射线吸收光谱 (XAS) 和电子之间的相互作用 顺磁共振（EPR）在我们的理解中发挥了重要作用 O(2) 演化的结构和机制方面。氧化 Mn 的状态以及 Mn 配合物在进展过程中的结构变化 通过 X 射线吸收光谱测定酶促循环 使用 EPR 光谱表征的样品。氧化态是 通过 Mn K 边和 L 边光谱以及高分辨率 X 射线测定 荧光光谱。中间体的结构表征 使用通过闪光照明制备的样品通过 XAS 进行。辅因子的作用 Ca(2+) 和 C1(-) Br(-) 通过 Ca (Sr) 和 C1 (Br) K 边缘 XAS 寻址 分别。