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Studies on Molecular Mechanisms for Carboxylation of RuBisCO toward High Efficiency

RuBisCO高效羧化的分子机制研究

基本信息

批准号：
10305065
负责人：
KAI Yasushi
金额：
$ 24万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

In these three years from 1998 to 2000, we could determine several threedimensional structures of RuBisCO, ribulose bis-phosphate carboxylase/oxygenase. Based on these structures, new structural principal to control the enzymatic function of RuBisCO was proposed.RuBisCO catalyses both reactions of carboxylation and oxygenation. Therefore, it is important to increase carboxylation/oxygenation ratio to design carboxylase with higher efficiency. RuBisCO has divalent magnesium ion on its active center. When the ion is replaced by manganese, the carboxylation activity decreases. In order to find some structural factor in these functional change, the crystal structure of manganese binding spinach RuBisCO.There exists so-called loop-6 with flexible structure near the active site of RuBisCO.The loop takes open structure when the substrate ribulose bis-phosphate is not near the active site, while it takes closed structure when the substrate is near the active site. The loop has lysine residue in the middle and fix the reaction intermediate formed from substrate and carbon dioxide. RuBisCO obtained from red algae Galdieria partita was found to have closed structure even though it has no reaction intermediate analogue in its active center. From the detailed comparison of the structure with other RuBisCOs, a new interaction was found to participates the open-close control of loop-6.RuBisCO of green algae Chlamydomonas reinhardtii has been well investigated in its enzymatic functions, while little of its structure was known. We have determined its three-dimensional structure for the first time and found the little difference in its large subunit, while marked difference in its small subunit resulted in the narrow solvent channel formed in the center of RuBisCO molecule.

在1998年至2000年的三年中，我们确定了RuBisCO，核酮糖二磷酸羧化酶/加氧酶的几个三维结构。在此基础上，提出了RuBisCO的结构控制原理：RuBisCO催化羧化反应和氧化反应。因此，提高羧化/加氧比对设计高效羧化酶具有重要意义。RuBisCO的活性中心含有二价镁离子。当离子被锰取代时，羧化活性降低。为了寻找这些功能变化中的结构因素，我们对锰结合菠菜RuBisCO的晶体结构进行了研究，发现在RuBisCO的活性中心附近存在一个具有柔性结构的loop-6，当底物核酮糖二磷酸不在活性中心附近时，loop-6呈开放结构，当底物核酮糖二磷酸在活性中心附近时，loop-6呈封闭结构。该环中间有赖氨酸残基，并固定底物和二氧化碳形成的反应中间体。从红藻Galdieria partita中得到的RuBisCO具有封闭的结构，尽管其活性中心没有反应中间体类似物。通过与其他RuBisCO的结构比较，发现一种新的相互作用参与了loop-6的开闭控制。绿色藻类莱茵衣藻（Chlamydellareinhardtii）的RuBisCO在酶功能方面已得到了很好的研究，但其结构尚不清楚。首次测定了其三维结构，发现其大亚基结构差异不大，而小亚基结构差异显著，导致RuBisCO分子中心形成狭窄的溶剂通道。