Role of each amino acid in electron transfer protein of photosynthesis

光合反应中心复合物上的蛋白质-表面氨基酸被检查在蛋白质-蛋白质相互作用中的每个氨基酸的作用。利用结合在紫色细菌反应中心复合物上的细胞色素亚基。细胞色素亚基具有良好的遗传系统，由本研究小组构建，以引入定点突变。并对氨基酸在进化过程中的保守性和变化及其与环境变化的关系进行了研究。在为期两年的调查中，取得了以下结果.在可溶性电子供体向反应中心的细胞色素亚基输入电子的位点上，明胶红球菌中的酸性氨基酸转变为疏水性氨基酸.在嗜硫红球菌中，细胞色素亚基中结合血红素的数量为3，而不是正常的4。这被认为是自然突变的结果。亚基中第四个血红素的氨基酸丢失，而这些氨基酸对血红素结合起重要作用.将绿色B.viridis细胞色素亚基的基因成功地导入到明胶红球菌的细胞中。利用这种杂交系统，我们现在可以将定点突变引入到结构已经精细解析的蛋白质中.在B.viridis中，酸性氨基酸对于与电子供体的相互作用是唯一重要的，但在R.gelatinosus中疏水性氨基酸也很重要。结合光合生物的进化，从基因表达和光能传递的氧化环境适应性方面，获得了一些新的信息。

Protein-surface amino acids on the photosynthetic reaction center complex were examined in terms of the role of each amino acid in the protein-protein interaction. The cytochrome subunit bound to the reaction center complex of purple bacteria was used. The cytochrome subunit has a good genetic system, constructed by this investigator's group, to introduce site-directed mutagenesis. The conservation and changes of amino acids during evolution and their relation to environmental changes were also studied. During the two-year investigation, following results were obtained.1. On the site of electron input to the cytochrome subunit of the reaction center from solubule electron donors, an acidic amino acid were changed to hydrophobic amino acid in R.gelatinosus.2. In R.sulfidophilum, the number of bound hemes in the cytochrome subunit was 3 instead of normal number of 4. This was considered as results of natural mutation. Amino acids which are important for heme binding have been lost for the forth heme in the subunit.3. The gene for the cytochrome subunit of B.viridis was successfully introduced to the cells of R.gelatinosus. Using this hybrid system, we can now introduce site-directed mutagenesis to the protein which structure has been finely solved.4. In B.viridis, acidic amino acids are solely important for the interaction with electron donors, but in R.gelatinosus hydrophobic amino acids are also important.5. With relation to the evolution of photosynthetic organisms, several pieces of new information about the oxidative environment adaptation of the gene expression and light-energy transfer.