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Function of phosphatidylglycerol in assembly and stabilization of photosynthetic machinery

磷脂酰甘油在光合机器组装和稳定中的作用

基本信息

批准号：
16570029
负责人：
WADA Hajime
金额：
$ 2.43万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

项目摘要

Phosphatidylglycerol (PG) is one of the ubiquitous lipid components in thylakoid membranes from chloroplasts and cyanobacteria. The major lipids found in thylakoid membranes are glycolipids and the phospholipid PG. Because PG is the only phospholipid in thylakoid membranes and is a negatively charged molecule at neutral pH, it is likely that PG mediates indispensable interactions with the components of photosynthetic complexes in thylakoid membranes and that PG plays a specific role in photosynthesis for which glycolipids cannot substitute.In this study, we have investigated the function of PG in assembly and stabilization of photosynthetic machinery with the pgsA mutant of the cyanobacterium Synechocystis sp. PCC6803, which is defective for the biosynthesis of PG. The present study shows that PG also plays an important role in the electron donor side of PSII, namely the oxygen-evolving system. Detailed analyses of purified PSII complexes indicated that PSII from PG-depleted pgsA mutant cells sustained only 〜50% of the oxygen-evolving activity compared to wild-type cells. Dissociation of the extrinsic proteins PsbO, PsbV, and PsbU, which are required for stabilization of the Mn-cluster, followed by the release of a manganese atom, was observed in PSII of the PG-depleted mutant cells. The released PsbO re-bound to PSII when PG was added back to the PG-depleted mutant cells, even when de novo protein synthesis was inhibited. Changes in photosynthetic activity of the PG-depleted pgsA mutant cells induced by heat treatment or dark incubation resembled those of ΔpsbO, ΔpsbV and ΔpsbU mutant cells. These results suggest that PG plays an important role in the binding of extrinsic proteins required for sustaining a functional Mn-cluster on the donor side of PSII.

磷脂酰甘油（PG）是叶绿体和蓝藻类囊体膜中普遍存在的脂质成分之一。在类囊体膜中发现的主要脂质是糖脂和磷脂PG。由于PG是类囊体膜中唯一的磷脂，并且在中性pH下是带负电荷的分子，因此PG可能介导与类囊体膜中光合复合物组分的不可或缺的相互作用，并且PG在光合作用中起着糖脂不能替代的特定作用。在这项研究中，本研究以聚胞藻6803中PG生物合成缺陷的pgsA突变体为材料，研究了PG在光合机构组装和稳定中的作用，发现PG在PS Ⅱ的电子供体侧，即放氧系统中也起着重要作用。纯化的PSII复合物的详细分析表明，从PG-耗尽的pgsA突变体细胞的PSII持续的氧释放活性相比，野生型细胞只有约50%。解离的外源蛋白PsbO，PsbV，和PsbU，这是所需的Mn-簇的稳定，随后由锰原子的释放，观察到在PSII的PG耗尽突变细胞。释放的PsbO重新绑定到PSII时，PG被添加回PG耗尽的突变体细胞，即使从头蛋白质合成被抑制。热处理或暗培养诱导的PG缺失的pgsA突变体细胞的光合活性变化类似于ΔpsbO、ΔpsbV和ΔpsbU突变体细胞。这些结果表明，PG起着重要的作用，在外部蛋白的结合所需的维持功能锰簇的供体侧PSII。