Photosystem II (PSII) is a light-driven protein, involved in the primary reactions of photosynthesis. In plant photosynthetic membranes PSII forms large multisubunit supercomplexes, containing a dimeric core and up to four light-harvesting complexes (LHCs), which act as antenna proteins. Here we solved a three-dimensional (3D) structure of the C2S2M2 supercomplex from Arabidopsis thaliana using cryo-transmission electron microscopy (cryo-EM) and single-particle analysis at an overall resolution of 5.3 Å. Using a combination of homology modelling and restrained refinement against the cryo-EM map, it was possible to model atomic structures for all antenna complexes and almost all core subunits. We located all 35 chlorophylls of the core region based on the cyanobacterial PSII structure, whose positioning is highly conserved, as well as all the chlorophylls of the LHCII S and M trimers. A total of 13 and 9 chlorophylls were identified in CP26 and CP24, respectively. Energy flow from LHC complexes to the PSII reaction centre is proposed to follow preferential pathways: CP26 and CP29 directly transfer to the core using several routes for efficient transfer; the S trimer is directly connected to CP43 and the M trimer can efficiently transfer energy to the core through CP29 and the S trimer.

Aix Marseille Université CEA CNRS BIAM Laboratoire de Génétique et Biophysique des Plantes 13009 Marseille France

Centre of the Region Haná for Biotechnological and Agricultural Research Department of Biophysics Faculty of Science Palacký University Šlechtitelů 27 783 71 Olomouc Czech Republic

Electron microscopy and Protein crystallography group Groningen Biomolecular Sciences and Biotechnology Institute University of Groningen 9747 AG Groningen The Netherlands

References provided by Crossref.org

Photosystem II supercomplexes lacking light-harvesting antenna protein LHCB5 and their organization in the thylakoid membrane

Cryo-EM structure of a plant photosystem II supercomplex with light-harvesting protein Lhcb8 and α-tocopherol

Spruce versus Arabidopsis: different strategies of photosynthetic acclimation to light intensity change

A kaleidoscope of photosynthetic antenna proteins and their emerging roles

Size and Fluorescence Properties of Algal Photosynthetic Antenna Proteins Estimated by Microscopy

Towards spruce-type photosystem II: consequences of the loss of light-harvesting proteins LHCB3 and LHCB6 in Arabidopsis

Revealing the architecture of the photosynthetic apparatus in the diatom Thalassiosira pseudonana

Unique organization of photosystem II supercomplexes and megacomplexes in Norway spruce

Ycf48 involved in the biogenesis of the oxygen-evolving photosystem II complex is a seven-bladed beta-propeller protein