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标题：Structure of a C2S2M2N2-type PSII–LHCII supercomplex from the green alga Chlamydomonas reinhardtii
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作者：Liangliang Shen ; Liangliang Shen ; Zihui Huang 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2019
卷号：116
期号：42
页码：21246-21255
DOI：10.1073/pnas.1912462116
出版社：The National Academy of Sciences of the United States of America
摘要：Photosystem II (PSII) in the thylakoid membranes of plants, algae, and cyanobacteria catalyzes light-induced oxidation of water by which light energy is converted to chemical energy and molecular oxygen is produced. In higher plants and most eukaryotic algae, the PSII core is surrounded by variable numbers of light-harvesting antenna complex II (LHCII), forming a PSII–LHCII supercomplex. In order to harvest energy efficiently at low–light-intensity conditions under water, a complete PSII–LHCII supercomplex (C 2 S 2 M 2 N 2 ) of the green alga Chlamydomonas reinhardtii (Cr) contains more antenna subunits and pigments than the dominant PSII–LHCII supercomplex (C 2 S 2 M 2 ) of plants. The detailed structure and energy transfer pathway of the Cr-PSII–LHCII remain unknown. Here we report a cryoelectron microscopy structure of a complete, C 2 S 2 M 2 N 2 -type PSII–LHCII supercomplex from C. reinhardtii at 3.37-Å resolution. The results show that the Cr-C 2 S 2 M 2 N 2 supercomplex is organized as a dimer, with 3 LHCII trimers, 1 CP26, and 1 CP29 peripheral antenna subunits surrounding each PSII core. The N-LHCII trimer partially occupies the position of CP24, which is present in the higher-plant PSII–LHCII but absent in the green alga. The M trimer is rotated relative to the corresponding M trimer in plant PSII–LHCII. In addition, some unique features were found in the green algal PSII core. The arrangement of a huge number of pigments allowed us to deduce possible energy transfer pathways from the peripheral antennae to the PSII core..
关键词：photosynthesis ; cryoelectron microscopy ; photosystem II ; light;harvesting complex ; structural analysis