Structural basis for energy transfer in a huge diatom PSI-FCPI supercomplex

• Published in: Nature communications Vol. 11; no. 1; pp. 5081 - 12
• Main Authors: Xu, Caizhe, Pi, Xiong, Huang, Yawen, Han, Guangye, Chen, Xiaobo, Qin, Xiaochun, Huang, Guoqiang, Zhao, Songhao, Yang, Yanyan, Kuang, Tingyun, Wang, Wenda, Sui, Sen-Fang, Shen, Jian-Ren
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 08.10.2020; Nature Portfolio
• Subjects: 101/28; 631/449/1734/2075; 631/45/535/1258/1259; 631/57/1464; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-020-18867-x

Diatom is an important group of marine algae and contributes to around 20% of the global photosynthetic carbon fixation. Photosystem I (PSI) of diatoms is associated with a large number of fucoxanthin-chlorophyll a / c proteins (FCPIs). We report the structure of PSI-FCPI from a diatom Chaetoceros gracili s at 2.38 Å resolution by single-particle cryo-electron microscopy. PSI-FCPI is a monomeric supercomplex consisting of 12 core and 24 antenna subunits (FCPIs), and 326 chlorophylls a , 34 chlorophylls c , 102 fucoxanthins, 35 diadinoxanthins, 18 β -carotenes and some electron transfer cofactors. Two subunits designated PsaR and PsaS were found in the core, whereas several subunits were lost. The large number of pigments constitute a unique and huge network ensuring efficient energy harvesting, transfer and dissipation. These results provide a firm structural basis for unraveling the mechanisms of light-energy harvesting, transfer and quenching in the diatom PSI-FCPI, and also important clues to evolutionary changes of PSI-LHCI. Diatoms are marine algae with an important role in global photosynthetic carbon fixation. Here, the authors present the 2.38 Å cryo-EM structure of photosystem I (PSI) in complex with its 24 fucoxanthin chlorophyll a/c -binding (FCPI) antenna proteins from the diatom Chaetoceros gracilis , which provides mechanistic insights into light-energy harvesting, transfer and quenching of the PSI-FCPI supercomplex.