Structure and Function of the Photosystem Supercomplexes

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.

Molecular dynamics simulations in photosynthesis

“…Photosynthetic pigments are bound to the proteins that constitute the cores of PSII and PSI and to the outer antennae: the light-harvesting complexes (LHCs) or the phycobilisomes (Croce and van Amerongen 2014). The light-harvesting complexes are functionally connected to the cores of PSII and PSI forming "supercomplexes" (Gao et al 2018). For a detailed review on the light-harvesting building blocks of photosynthetic organisms we refer the reader to Croce et al (2018).…”

Whirly1 enhances tolerance to chilling stress in tomato via protection of photosystem II and regulation of starch degradation

“…PSII is a major protein-pigment complex involved in photosynthetic electron transport in the chloroplast thylakoid membrane and is responsible for light-driven oxidation of water and reduction of plastoquinone. More than 20 different subunits have been found in PSII (Nelson & Yocum, 2006;Shi et al, 2012a;Gao et al, 2018). The reaction center protein D1 of PSII is the most vulnerable protein under various stress conditions (Allen & Ort, 2001;Nishiyama et al, 2006).…”

Proteoliposomes as energy transferring nanomaterials: enhancing the spectral range of light-harvesting proteins using lipid-linked chromophores

“…7 The membrane proteins which undertake photosynthetic light harvesting (LH) act in a conceptually similar way to a satellite dish, whereby antenna proteins channel energy towards Reaction Centre type proteins which perform photochemistry. 8 LH membrane proteins have a 3-D polypeptide structure which acts as a scaffold to precisely arrange chromophores at high density in such a manner that energy absorption and transfer are extremely efficient. 9 Light-harvesting complex II (LHCII) 10 acts as the primary antenna protein for plants and is estimated to be the most abundant membrane protein on Earth due to its high density in the membranes of chloroplasts.…”