The D2 Protein in Photosystem II: Its Involvement in PS II Structure and Function

这个项目有几个目标，都与功能有关。 D2是光系统II反应中心蛋白之一， 类囊体膜 使用定点突变和基因 来自蓝细菌的D2编码pbsD 1基因的替换 集胞藻属PCC 6803，第一个目的是确定 D2的C-末端附近的残基在水裂解中的作用 过程和D2的正确折叠。 此外，三- 参与水裂解的D2残基的空间邻近性 将通过分析自发的光合自养突变体来探索 由专性光异养定点D2突变体产生 在水分解中受损。 此外，定点突变 受体侧电子转移事件的研究 光系统II将强调与结合相关的实验， 光系统II反应中心的额外叶绿素 复合物以及非血红素铁在光系统II中的作用。 另一个目标，将与博士合作实现。 Shestakov和他的小组在莫斯科（苏联），是确定其他 D2蛋白中对光系统重要的区域 II通过psbD 1的随机诱变来发挥功能。 一个成功 预计该项目的完成将大大增加 关于单个氨基酸作用的知识基础 膜的功能、折叠和稳定组装中的残基 蛋白质如D2。 这个过程从太阳获取能量供生物使用 光合作用。 光捕获的过程是在 由两种色素蛋白复合物，光系统I和II。 光 光系统I吸收的能量被细胞用于碳 固定和化学能生产。 吸收的光能 光系统II是再生光系统I所必需的， 失去电子给细胞成分。 光系统II，反过来， 是通过水的分解而再生的，这个过程 氧气的存在，并解释了地球上的氧气 气氛 该提案描述了一种 蛋白质，D2，是光系统II的重要组成部分。 这些 研究将有助于阐明水分解的过程 在分子水平上发生。

This project has several objectives, all related to the function of D2, one of the photosystem II reaction center proteins in thylakoid membranes. Using site-directed mutagenesis and gene replacement in the D2-encoding pbsD1 gene from the cyanobacterium Synechocystis sp. PCC 6803, the first objective is to determine the role of residues near the C-terminus of D2 in the water-splitting process and in proper folding of D2. In addition, three- dimensional proximities of D2 residues involved in water splitting will be probed by analysis of spontaneous photoautotrophic mutants generated from obligate photoheterotrophic site-directed D2 mutants impaired in water splitting. Moreover, site-directed mutagenesis studies on electron transfer events at the acceptor side of photosystem II will emphasize experiments related to binding of additional chlorophyll(s) in the photosystem II reaction center complex as well as the role of the non-heme iron in photosystem II. Another objective, to be achieved in collaboration with Dr. Shestakov and his group in Moscow (USSR), is to identify other regions of the D2 protein that are important towards photosystem II function by random mutagenesis of psbD1. A successful completion of this project is anticipated to markedly increase the base of knowledge regarding the role of individual amino acid residues in function, folding and stable assembly of membrane proteins such as D2. Energy from the sun is captured for biological use by the process of photosynthesis. The process of light harvesting is carried out by two pigment-protein complexes, photosystems I and II. Light energy absorbed by photosystem I is used by the cell for carbon fixation and chemical energy production. Light energy absorbed by photosystem II is essential for regenerating photosystem I which loses electrons to cellular constituents. Photosystem II, in turn, is regenerated by the splitting of water, a process that liberates dioxygen and accounts for the presence of oxygen in the earth's atmosphere. This proposal describes molecular studies of a protein, D2, that is an essential part of photosystem II. These studies will help to elucidate how the process of water splitting occurs at the molecular level.//