Studies on the Photochemical Reaction Center Complexes of Photosynthesis

光合作用最重要的过程之一是将光能转化为化学能的光化学反应。进行光化学反应的各种蛋白质复合物是可用的，并用于本研究。（1）光系统II复合物--（a）蓝藻光系统II复合物中的质体醌被多种醌类化合物取代，发现四卤代苯与光系统II复合物的结合效率最高，是最有效的电子受体。(b)光系统II复合物的放氧活性被甘氨酸甜菜碱大大稳定。(2)光系统I复合物-（a）选择性破坏光系统I复合物的FeS中心，表明FeS中心A和B对电子传递都是必需的。(b)在与脂质体的重建实验中，有人建议，单半乳糖脂加速从捕光叶绿素蛋白的光系统I复合物的激发能量的转移。(3)细菌反应中心复合物-（a）来自太阳杆菌属的反应中心复合物含有两个细菌叶绿素g'分子和两个叶绿素a样色素分子。(b)本文研究了细菌叶绿素c在水饱和CCl_4溶液中形成的单体、二聚体、三聚体和聚合体的吸收光谱和圆二色谱。(4)光合作用基因：（a）我们从发芽的小麦中纯化了一种使质体DNA甲醇化的酶。(b)我们克隆了叶绿体基因组中编码光系统II复合物小多肽的基因。(c)将磷酸烯醇式丙酮酸羧化酶（PEPcase）基因的启动子区与报告基因连接，研究了PEPcase的组织特异性表达。NH_3能促进PEP酶C_4型基因的转录，但对C_3型基因的转录无影响。

One of the most important processes of photosynthesis is the photochemical reaction that converts light energy into chemical energy. Various kinds of protein complexes, which perform the photochemical reactions, are available, and are used in this study. The results are summarized as follows : (1) Photosystem II complex - (a) Plastoquinone of the cyanobacterial photosystem II complex was substituted by many kinds of quinone derivatives, and we found that tetrahalobenzene most efficienty bound to the photosystem II complex and was a most efficient electron acceptor. (b) The oxygen-evolving activity of the photosystem II complex was greatly stabilized by glycinebetaine.(2) Photosystem I complex - (a) Selective destruction of FeS centers of the photosystem I complex demonstrated that both FeS centers A and B are essential to the electron transport. (b) In the reconstitution experiment with liposomes, it was suggested that monogalactolipid accelerates the transfer of excitation energy from the light-harvesting chlorophyll protein to the photosystem I complex.(3) Bacterial reaction center complex - (a) The reaction center complex from Heliobacterium contained two molecules of bacteriochlorophyll g' and two molecules of a chlorophyll a-like pigment. (b) We studied the absorption and the CD spectra of monomer, dimer, trimer and polymer of Bacteriochlorophyll c which were formed in water - saturated CCl_4.(4) Photosynthesis genes - (a) We purified from germinating wheat an enzyme which methanolizes plastid DNA. (b) We cloned genes of the chloroplast genome which encode small polypeptides of the photosystem II complex. (c) The tissuespecific expression of phosphoenolpyruvate carboxylase (PEPcase) was studied by ligating the promoter region of PEPcase gene with a reporter gene. The transcription of the gene for the C_4 type, but not C_3 type, of PEPcase was enhanced by NH_3.