Structure and Function of the Photosystem Supercomplexes

Jinlan Gao,Hao Wang,Qipeng Yuan,Yue Feng

doi:10.3389/fpls.2018.00357

Abstract

Photosynthesis converts solar energy into chemical energy to sustain all life on earth by providing oxygen and food, and controlling the atmospheric carbon dioxide. During this process, the water-splitting and oxygen-evolving reaction is catalyzed by photosystem II (PSII), while photosystem I (PSI) generates the reducing power for the reduction of NADP+ to NADPH. Together with their peripheral light-harvesting complexes (LHCs), photosystems function as multisubunit supercomplexes located in the thylakoid membranes of cyanobacteria, algae, and plants. Recent advances in single-particle cryo-electron microscopy (cryoEM), X-ray free electron laser (XFEL) and other techniques have revealed unprecedented structural and catalytic details concerning the two supercomplexes. Several high-resolution structures of the complexes from plants were solved, and serial time-resolved crystallography and “radiation-damage-free” femtosecond XFEL also provided important insights into the mechanism of water oxidation. Here, we review these exciting advances in the studies of the photosystem supercomplexes with an emphasis on PSII-LHCII, propose presently unresolved problems in this field, and suggest potential tendencies for future studies.

Highlights

Photosynthesis carries out a series of biophysical and biochemical processes, converting solar energy into chemical energy
The complete photosynthetic reactions in cyanobacteria, algae and plants are executed by four major protein supercomplexes including photosystem I (PSI), photosystem II (PSII), cytochrome b6f and F-ATPase (Nelson and Benshem, 2004; Nelson and Yocum, 2006)
In 2009, Broser et al presented the first structure of a monomeric form of PSII core complex (PSIIcc) with high oxygen-evolution capacity from T. elongatus (Broser et al, 2010)

Summary

Introduction

Photosynthesis carries out a series of biophysical and biochemical processes, converting solar energy into chemical energy. We will review the recent progress in the studies into the structures and functions of photosystems of different origins, with an emphasis on PSII-LHCII. The complete photosynthetic reactions in cyanobacteria, algae and plants are executed by four major protein supercomplexes including PSI, PSII, cytochrome b6f (plastoquinone-plastocyanin oxidoreductase) and F-ATPase (proton-motive force-driven ATP synthase) (Nelson and Benshem, 2004; Nelson and Yocum, 2006).

Results

Conclusion