Structural determination of the large photosystem II?light-harvesting complex II supercomplex of Chlamydomonas reinhardtii using nonionic amphipol
Structural determination of the large photosystem II?light-harvesting complex II supercomplex of Chlamydomonas reinhardtii using nonionic amphipol
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DOI：
10.1074/jbc.ra119.009341
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发表时间：
2019-10-11
影响因子：
4.8
通讯作者：
Minagawa, Jun
中科院分区：
文献类型：
--
作者：
Burton-Smith, Raymond N.;Watanabe, Akimasa;Minagawa, Jun
在光合生物中，光系统II （PSII）是一个大的膜蛋白复合物，由一对核心复合物组成，周围是一系列可变数量的光收集复合物（LHC） II蛋白。先前报道的PSII结构？莱茵衣藻（Chlamydomonas reinhardtii）的LHCII超配合物表现出明显的结构异质性，但最近改进的使用离子双酚A8-35的纯化方法增强了超配合物的稳定性，为确定更完整的结构提供了机会。在这里，我们提出一个5.8 ？C. reinhardtii PSII？含有六个LHCII三聚体（C2S2M2L2）的LHCII超配合物。利用新开发的非离子双极性聚合物？基于纯化和稳定的方法，我们纯化了最大的光合超复合体，其完整构型的百分比是迄今为止报道的最高的。我们发现绿藻光系统中捕光复合物阵列内的蛋白间距离比以前在高等植物中观察到的要大，这表明PSII？绿藻中LHCII超配合物可能发生改变。有趣的是，我们还观察到不对称的PSII？同一样品中含有C2S2M1L1的LHCII超络合物结构。此外，我们在PSII核心复合物附近发现了一个新的密度，可归因于单跨膜螺旋。以前在PSII的冷冻电镜图中没有报道过。陆地植物的LHCII超配合物。
In photosynthetic organisms, photosystem II (PSII) is a large membrane protein complex, consisting of a pair of core complexes surrounded by an array of variable numbers of light-harvesting complex (LHC) II proteins. Previously reported structures of the PSII?LHCII supercomplex of the green alga Chlamydomonas reinhardtii exhibit significant structural heterogeneity, but recently improved purification methods employing ionic amphipol A8-35 have enhanced supercomplex stability, providing opportunities for determining a more intact structure. Herein, we present a 5.8 ? cryo-EM map of the C. reinhardtii PSII?LHCII supercomplex containing six LHCII trimers (C2S2M2L2). Utilizing a newly developed nonionic amphipol?based purification and stabilizing method, we purified the largest photosynthetic supercomplex to the highest percentage of the intact configuration reported to date. We found that the interprotein distances within the light-harvesting complex array in the green algal photosystem are larger than those previously observed in higher plants, indicating that the potential route of energy transfer in the PSII?LHCII supercomplex in green algae may be altered. Interestingly, we also observed an asymmetric PSII?LHCII supercomplex structure comprising C2S2M1L1 in the same sample. Moreover, we found a new density adjacent to the PSII core complex, attributable to a single-transmembrane helix. It was previously unreported in the cryo-EM maps of PSII?LHCII supercomplexes from land plants.