Revisiting the Supramolecular Organization of Photosystem II in Chlamydomonas reinhardtii*
Revisiting the Supramolecular Organization of Photosystem II in Chlamydomonas reinhardtii*
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DOI：
10.1074/jbc.m111.331991
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发表时间：
2012-07
期刊：
影响因子：
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通讯作者：
Ryutaro Tokutsu;Nobuyasu Kato;K. Bui;T. Ishikawa;J. Minagawa
中科院分区：
文献类型：
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作者：
Ryutaro Tokutsu;Nobuyasu Kato;K. Bui;T. Ishikawa;J. Minagawa
背景：捕光复合物II（LHCII）蛋白与光系统II（PSII）结合形成超复合物。结果如下：我们从用十二烷基-α-d-麦芽糖苷溶解的类囊体中分离出一个活性PSII超复合物，并用电子显微镜在大投影图中观察到它。结论：新型PSII超复合物每侧含有三个LHCII三聚体。意义：PSII-LHCII超复合物大而活跃，参与绿色藻类的光合作用。光系统II（PSII）是一种多蛋白复合物，在光合作用中分解水并启动电子转移。PSII的中心部分，即PSII核心，被捕光复合物II蛋白（LHCII）包围。在高等植物中，在PSII核心的每一侧都可以看到两个或三个LHCII三聚体，而在莱茵衣藻的相应位置上只能看到一个，这可能是由于缺少CP 24，一个次要的单体LHCII。在这里，我们重新研究了超分子组织的C。通过确定不同增溶洗涤剂的效果来确定莱茵衣藻PSII-LHCII超复合物。当我们用正十二烷基-β-d-麦芽糖苷（β-DM）或正十二烷基-α-d-麦芽糖苷（α-DM）溶解类囊体膜并进行凝胶过滤时，我们观察到分子量的明显差异。α-DM-增溶的PSII-LHCII超复合物比β-DM-增溶的超复合物结合2倍以上的LHCII，并保持更高的放氧活性。对α-DM增溶和负染超复合物的电子显微照片进行单粒子图像分析，发现PSII-LHCII超复合物具有一种新型的超分子结构，核心的每一侧都连接着三个LHCII三聚体。
Background: Light-harvesting complex II (LHCII) proteins associate with photosystem II (PSII) to form a supercomplex. Results: We isolated an active PSII supercomplex from thylakoids solubilized with dodecyl-α-d-maltoside and visualized it in a large projection map with an electron microscope. Conclusion: The novel PSII supercomplex harbored three LHCII trimers on each side. Significance: The large and active PSII-LHCII supercomplex is engaged in green algal photosynthesis. Photosystem II (PSII) is a multiprotein complex that splits water and initiates electron transfer in photosynthesis. The central part of PSII, the PSII core, is surrounded by light-harvesting complex II proteins (LHCIIs). In higher plants, two or three LHCII trimers are seen on each side of the PSII core whereas only one is seen in the corresponding positions in Chlamydomonas reinhardtii, probably due to the absence of CP24, a minor monomeric LHCII. Here, we re-examined the supramolecular organization of the C. reinhardtii PSII-LHCII supercomplex by determining the effect of different solubilizing detergents. When we solubilized the thylakoid membranes with n-dodecyl-β-d-maltoside (β-DM) or n-dodecyl-α-d-maltoside (α-DM) and subjected them to gel filtration, we observed a clear difference in molecular mass. The α-DM-solubilized PSII-LHCII supercomplex bound twice more LHCII than the β-DM-solubilized supercomplex and retained higher oxygen-evolving activity. Single-particle image analysis from electron micrographs of the α-DM-solubilized and negatively stained supercomplex revealed that the PSII-LHCII supercomplex had a novel supramolecular organization, with three LHCII trimers attached to each side of the core.