STRUCTURE AND ROLE OF THE CALCIUM COFACTOR IN PHOTOSYNTHETIC OXYGEN EVOLUTION

钙辅助因子在光合作用释氧中的结构和作用

• 批准号: 8169975
• 负责人: VITTAL YACHANDRA
• 金额: $ 1.36万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-05-01 至 2011-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8169975
• 关键词: Algae; Binding; Binding Sites; Biochemical; Calcium; Charge; Computer Retrieval of Information on Scientific Projects Database; Couples; Cyanobacterium; Dioxygen; Electrons; Evolution; Funding; Grant; Institution; Investigation; Membrane; Oxygen; Plants; Proteins; Protons; Relative (related person); Research; Research Personnel; Resources; Role; Sampling; Site; Source; Structure; Thylakoid Membranes; United States National Institutes of Health; Water; cofactor; oxidation; photosystem II; research study; vector

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Photosynthetic water oxidation takes place within Photosystem II (PS II), which is embedded in the thylakoid membranes of green plants, cyanobacteria and algae. Within PS II, the Mn cluster couples the one electron primary charge separation (photo-oxidation) with the four-electron water oxidation cycling through ?S-states? S0 through S4, storing oxidative equivalents serially until it reaches S4, whereupon it oxidizes two substrate water molecules to dioxygen, and returns to the S0 state. Calcium is an essential cofactor and without it the OEC cannot catalyze the oxidation of water into dioxygen, protons, and electrons. Calcium has been shown to be essential for the S2 to S3 state transition and subsequent oxygen evolution. Both XANES and EXAFS experiments have been carried out at the Mn K-edge of the OEC to determine the oxidation states and structural information about the Mn site. In comparison, there have been fewer spectroscopic investigation of the calcium cofactor. Most studies on Ca in PSII have been biochemical, because Ca has no easy spectroscopic handle. The structure of the Ca cofactor binding site has generated considerable discussion. To probe it, Ca in OEC might be substituted by Sr chemically or biochemically by growing cyanobacteria in Ca depleted Sr media, which binds at the Ca site within the protein. Under previous proposals our group has carried out Ca and Sr K-edge EXAFS experiments to resolve the question of proximity of the Ca/Sr to the Mn4-cluster of OEC. By using Ca EXAFS of the native PS II and Sr EXAFS on Sr-reactivated PS II membranes we have confirmed the proximity of the Ca/Sr at 3.5A to the Mn-cluster in the S1 dark stable state of the OEC. Using polarized Sr EXAFS on oriented Sr-reactivated samples the averaged Sr-Mn vector orientation relative to the membrane normal was determined to be within 0-23 degree. The present challenge is to determine the Mn4-Ca interactions.

该副本是利用众多研究子项目之一 由NIH/NCRR资助的中心赠款提供的资源。子弹和 调查员（PI）可能已经从其他NIH来源获得了主要资金， 因此可以在其他清晰的条目中代表。列出的机构是 对于中心，这不一定是调查员的机构。 光合水氧化发生在光系统II（PS II）内，该（PS II）嵌入了绿色植物，蓝细菌和藻类的类囊体膜中。在PS II中，MN群集将一个电子主电荷分离（光氧化）与四电子水氧化循环通过？s态？ S0至S4，串行氧化等效物，直到达到S4为止，因此它将两个底物水分子氧化为二恶英，然后返回到S0状态。钙是必不可少的辅助因子，没有它，OEC将无法将水氧化成二恶英，质子和电子。钙已被证明对于S2至S3状态过渡和随后的氧气进化至关重要。 XANE和EXAFS实验均在OEC的Mn K边缘进行，以确定有关MN位点的氧化态和结构信息。相比之下，钙辅助因子的光谱研究较少。大多数对PSII中CA的研究都是生化的，因为CA没有容易的光谱手柄。 CA辅因子结合位点的结构引起了广泛的讨论。为了探究它，OEC中的CA可以通过在Ca耗尽的SR培养基中生长的蓝细菌在化学上或生物化学上取代，从而在蛋白质内的CA位点结合。 根据先前的建议，我们的小组已经进行了CA和SR K边缘EXAFS实验，以解决CA/SR与MN4群体OEC的接近性问题。通过在SR反应的PS II膜上使用天然PS II和SR EXAF的CA EXAFS，我们已经在3.5A时证实了CA/SR在OEC的S1黑暗状态下的CA/SR与Mn-Cluster的接近度。使用偏振SR EXAFS在定向的SR反应样品上使用平均的SR-MN矢量取向相对于膜法线，确定为0-23度。目前的挑战是确定MN4-CA相互作用。