STRUCTURE/FUNCTION OF THE MN OXYGEN EVOLVING COMPLEX

MN 放氧复合物的结构/功能

• 批准号: 2634831
• 负责人: VITTAL YACHANDRA
• 金额: $ 20.44万
• 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 2000-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2634831
• 关键词: X ray spectrometry; bromine; calcium ion; catalase; chloride ion; cofactor; electron spin resonance spectroscopy; manganese; metalloenzyme; protein structure function; strontium; superoxide dismutase

DESCRIPTION: 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 of dioxygen in Photosystem II. Oxygen, that 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 processes 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 cofactors C1(-) and Ca(2+). The interplay between XAS and 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. The structure of the intermediates are characterized by XAS using samples prepared by flash illumination. The role of cofactors Ca(2+)(Sr(2+) and C1(-) (Br-) is addressed by Ca(Sr) and Cl (Br) K-edge XAS respectively.

描述：含锰的金属蛋白具有氧化还原活性作用 参与各种生理上重要的反应，包括 氧气代谢。其中包括一种超氧化物歧化酶。 将超氧阴离子自由基解毒为O(2)和过氧化氢，一种过氧化氢酶 使过氧化氢不成比例地生成O(2)和H(2)O，一种核苷酸还原酶 催化合成脱氧核糖核苷酸，可能是最 复杂而重要的含锰析氧络合物(Mn-OEC) 这与光系统II中氧气水的氧化有关。 支持所有有氧生命的氧气在大气中非常丰富。 因为它通过光合作用的水氧化作用不断再生 MN-OEC。光诱导水氧化成氧气是其中的一种 最重要的化学过程发生在如此大规模的 生物圈。光合作用的水氧化包括去除四个 两个水中的电子，通过光诱导氧化以一种逐步的方式 分子由Mn-OEC产生一个氧分子。中心问题 需要解决的问题，这项提案的总体目标是 1)测定四种中间体中锰的氧化态 或S态，2)表征了氧桥联的结构变化 四核锰络合物在酶循环中的进展，3) 确定水氧化和放氧的机理，4) 阐明辅因子C1(-)和辅因子的结构和功能作用 Ca(2+)。XAS和EPR之间的相互作用在以下方面发挥了重要作用 我们对O(2)的结构和力学方面的理解 进化论。锰的氧化态及其结构变化 在酶循环中推进的复合体是由X射线确定的 吸收光谱利用EPR光谱对样品进行表征。 用Mn K边光谱和L边光谱确定了氧化态。这个 用XAS对中间体的结构进行了表征 由闪光照明制备。辅因子Ca(2+)(Sr(2+)和 C_1(-)(B_r-)分别由Ca(Sr)和C_1(B_R)K-EDGE XAS寻址。