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Structural biology of carboxylases in C4 plant

C4 植物中羧化酶的结构生物学

基本信息

批准号：
13450353
负责人：
KAI Yasushi
金额：
$ 9.6万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-13450353/
关键词：
C4 plant Maize Carboxylase PEP carboxylase Effector PEPC-Protein Kinase X-ray analysis Molecular mechanism

项目摘要

Phosphoenolpyruvate carboxylase (PEPC) catalyzes the first step in the fixation of atmospheric CO_2 during C_4 photosynthesis. The crystal structure of C_4-form maize PEPC, the first structure of the plant PEPCs, has been determined at 3.0 A^^○ resolution. The structure includes a sulfate ion at the plausible binding site of an allosteric activator, glucose 6-phosphate. The crystal structure of E. coli PEPC complexed with Mn2^<2+>, phosphoenolpyruvate analogue (3,3-dichloro-2-dihydroxyphosphinoylmethyl-2-propenoate), and an allosteric inhibitor, aspartate, has also been determined at 2.35 A^^○ resolution. Dynamic movements were found in the maize PEPC structure around two loops near the active site, compared with E. coli PEPC. Based on these molecular structures, the mechanisms for the carboxylation reaction and for the allosteric regulation of PEPC are proposed.Ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) is the initial step enzyme in the Calvin-Benson cycle of photosynthesis. It catalyzes the addition of gaseous CO_2 to ribulose 1,5-bisphosphate and produces two molecules of 3-phosphoglycerate. However, this enzyme also catalyzes O_2 addition for RuBP as the primary reaction of photorespiration. The crystal structure of Rubisco from Chlamydomonas has also been determined at 1.84 A^^○ resolution. The present high-resolution structure has revealed novel post-translational modifications. The crystal structure of unactivated Galdieria Rubisco has also been determined at 2.6 A^^○ resolution. The electron density map reveals that a sulfate binds only to the P1 anion-binding site of the active site and the loop 6 is closed. This interaction is likely to be crucial to understanding for stabilizing the loop 6 in the close state and to making a higher affinity for anionic ligands.

磷酸烯醇式丙酮酸羧化酶（PEPC）是C_4光合作用中固定大气CO_2的第一步催化酶。在3.0 A^^○分辨率下测定了植物PEPC的第一结构--玉米PEPC的C_4型晶体结构。该结构包括在变构激活剂葡萄糖6-磷酸的合理结合位点处的硫酸根离子。对E.与Mn 2 ^<2+>、磷酸烯醇式丙酮酸类似物（3，3-二氯-2-二羟基膦基甲基-2-丙烯酸酯）和别构抑制剂天冬氨酸形成复合物的大肠杆菌PEPC也在2.35埃的分辨率下被测定。与E. coli PEPC。根据这些分子结构，提出了PEPC羧化反应和变构调节的机理。核酮糖1，5-二磷酸羧化酶/加氧酶（RuBisCO）是光合作用Calvin-Benson循环的起始酶。它催化气态CO_2与1，5-二磷酸核酮糖的加成，生成两个分子的3-磷酸甘油酸。同时，该酶也催化RuBP的O_2加成反应，作为光呼吸的初级反应。来自衣原体的Rubisco的晶体结构也在1.84埃的分辨率下被确定。目前的高分辨率结构揭示了新的翻译后修饰。未活化的Galdieria Rubisco的晶体结构也在2.6埃的分辨率下被确定。电子密度图显示，硫酸根仅与活性位点的P1阴离子结合位点结合，环6闭合。这种相互作用对于理解稳定闭合状态下的环6和对阴离子配体产生更高的亲和力可能是至关重要的。