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Molecular machinery regulating energy and metabolic networks in plant cells

调节植物细胞能量和代谢网络的分子机器

基本信息

批准号：
15GS0320
负责人：
HASE Toshiharu
金额：
$ 209.83万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Creative Scientific Research
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2007
项目状态：
已结题

项目摘要

Plants synthesize various biomaterials through the reductive assimilation of inorganic carbon and nitrogen compounds. In these metabolic processes, an electron carrier protein, ferredoxin (Fd) plays a main role as an electron donor in the networks of energy and metabolic pathways. This study focused structures and functions of molecular machineries in these networks. Three projects were planed; 1) elucidation-of redox cascades via Fd in chloroplasts and nonphotosynthetic plastids, 2) determination of the structures of electron transfer complexes between Fd and partner enzymes, and 3) study of regulatory basis of these network in light of the electron partitioning.Following results have been obtained. 1) Structures of leaf-type Fd, FNR and their complex, root-type Fd, FNR and their complex, SiR, and complex of Fd and SiR were determined by x-ray crystallographic analysis. In these 3 complexes, different molecular surface of Fd were contributed as the area for the interaction of each partner enzyme. The distances between redox centers in the complexes are different, but a through-space electron transfer seems to operate in both cases. 2) Protein-protein interaction in the complexes of Fd: FNR and Fd: SiR were elucidated by NMR analysis and the molecular recognition in solution state agrees well with that in crystal. 3) Knock-out mutant of FNR and knock-down mutant of Fd in Arabidopsis were selected. The resulting mutants, in which amounts of FNR and Fd and sub-chloroplast distribution of FNR were changed, showed an alteration in the electron partitioning between carbon and nitrogen assimilation, decrease in non-cyclic electron transfer level, and increase in reducing state level of photosystem II. These phenomena indicated the absolute amount of Fd and FNR, and their ratio are crucial factors for determination of electron availability and partitioning in chloroplasts.

植物通过还原同化无机碳和氮化合物合成各种生物材料。在这些代谢过程中，电子载体蛋白铁氧还蛋白（Fd）作为能量和代谢途径网络中的电子供体发挥着主要作用。本研究主要关注这些网络中分子机器的结构和功能。计划了三个项目;（1）阐明了叶绿体和非光合质体中Fd的氧化还原级联反应，（2）测定了Fd与配偶酶之间电子传递复合物的结构，（3）根据电子分配研究了这些网络的调控基础。1)用X射线晶体学方法测定了叶型Fd、FNR及其复合物、根型Fd、FNR及其复合物、SiR以及Fd与SiR复合物的结构。在这3种复合物中，Fd的不同分子表面被贡献为每个伴侣酶相互作用的面积。复合物中氧化还原中心之间的距离是不同的，但通过空间电子转移似乎在两种情况下操作。2)通过核磁共振谱分析，证实了Fd：FNR和Fd：SiR复合物中蛋白质-蛋白质相互作用的存在，其溶液和晶体中的分子识别结果一致。3)选择拟南芥FNR基因敲除突变体和Fd基因敲除突变体。由此产生的突变体，其中FNR和Fd的量和亚叶绿体分布的FNR的变化，表现出碳和氮同化之间的电子分配的改变，非循环电子传递水平的降低，并增加光系统II的还原态水平。这些现象表明，Fd和FNR的绝对量及其比值是决定叶绿体电子有效性和分配的关键因素。