The Function of PsbO, the Photosystem II Manganese-Stabilizing Protein

PsbO（光系统 II 锰稳定蛋白）的功能

• 批准号: 0716541
• 负责人: Charles Yocum
• 金额: $ 48.06万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-01 至 2012-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0716541&HistoricalAwards=false
• 关键词: Function; PsbO; Photosystem; II; Manganese

One of the key reactions of photosynthesis is the conversion of water into the oxygen in the atmosphere, which is catalyzed by an enzyme system called photosystem II. Photosystem II binds the chlorophyll molecules that absorb the light energy required for oxygen production, as well as the atoms of manganese, calcium and chloride that form the site of oxygen production in the enzyme. The enzyme consists of a number of proteins that anchor it in a membrane, but it also contains three proteins that are not associated with the membrane. Removal of one of these proteins, called PsbO, or ''manganese-stabilizing protein'' from the enzyme causes a loss of calcium and chloride cofactors and a loss of oxygen production as well. This research project addresses the role of PsbO in oxygen production. A series of genetically modified PsbO proteins have been developed with prior support from NSF; some of these proteins exhibit an interesting modification in their ability to rebind to photosystem II. Normally, two copies of the protein are present. Mutant proteins are available that exhibit binding of two, only one or of no copies of PsbO. The consequences of these modified protein stoichiometries on cofactor binding and stability of manganese retention will be determined. In addition, mutations in PsbO that modify amino acids that may be required for calcium binding will be characterized, and experiments will be carried out to determine whether PsbO might form part of a channel that conducts water to the site of oxygen formation in the enzyme. Results of this research project will provide more information on the unique chemistry of oxygen evolution, a reaction that may some day be used in synthetic systems for energy production.Broader ImpactsA principle aim of this project is to provide hands on research experience for undergraduate students who are majoring in the life sciences. A number of the experiments in the project involve site-directed mutagenesis, protein overexpression and purification, and enzyme assays. The goal is to have two undergraduates working in the laboratory at any given time. The Co-P.I. will obtain experience in mentoring undergraduates as part of this effort, and the students will be encouraged to present their results at regional meetings. A junior faculty member who teaches chemistry at Spring Arbor University will collaborate in this project so as to provide him with research facilities that can be combined with his teaching activities. Finally, the P.I. teaches two undergraduate courses (biochemistry, plant molecular biology) in which lectures on photosynthesis, and discussions of the research literature form an important part of the offerings.

光合作用的关键反应之一是将水转化为大气中的氧气，这是由一种称为光系统II的酶系统催化的。光系统II结合了吸收产氧所需光能的叶绿素分子，以及在酶中形成产氧位点的锰、钙和氯原子。这种酶由许多将其固定在膜上的蛋白质组成，但它也含有三种与膜无关的蛋白质。从酶中去除其中一种称为PsbO或“锰稳定蛋白”的蛋白质会导致钙和氯化物辅助因子的损失，也会导致氧气生产的损失。本研究项目探讨了PsbO在产氧中的作用。在NSF的支持下，一系列基因修饰的PsbO蛋白已经被开发出来；其中一些蛋白质在重新结合光系统II的能力上表现出一种有趣的改变。正常情况下，这种蛋白质有两个拷贝。突变蛋白可以结合两个，只有一个或没有PsbO拷贝。这些修饰的蛋白质化学计量对辅因子结合和锰保留稳定性的影响将被确定。此外，PsbO中修饰钙结合所需氨基酸的突变将被表征，并将进行实验以确定PsbO是否可能形成将水输送到酶中氧形成位点的通道的一部分。这个研究项目的结果将提供更多关于氧气演化的独特化学信息，这一反应可能有一天会被用于能源生产的合成系统。更广泛的影响该项目的主要目的是为主修生命科学的本科生提供动手研究经验。该项目的一些实验涉及定点诱变、蛋白质过表达和纯化以及酶分析。我们的目标是在任何时候都有两名本科生在实验室工作。Co-P.I。将获得指导本科生的经验，并鼓励学生在区域会议上展示他们的成果。一位在春树大学教授化学的初级教师将参与这个项目，为他提供可以与他的教学活动相结合的研究设施。最后，P.I.教授两门本科课程（生物化学、植物分子生物学），其中光合作用的讲座和研究文献的讨论是课程的重要组成部分。