Core and rod structures of a thermophilic cyanobacterial light-harvesting phycobilisome

Cyanobacteria, glaucophytes, and rhodophytes utilize giant, light-harvesting phycobilisomes (PBSs) for capturing solar energy and conveying it to photosynthetic reaction centers. PBSs are compositionally and structurally diverse, and exceedingly complex, all of which pose a challenge for a comprehensive understanding of their function. To date, three detailed architectures of PBSs by cryo-electron microscopy (cryo-EM) have been described: a hemiellipsoidal type, a block-type from rhodophytes, and a cyanobacterial hemidiscoidal-type. Here, we report cryo-EM structures of a pentacylindrical allophycocyanin core and phycocyanin-containing rod of a thermophilic cyanobacterial hemidiscoidal PBS. The structures define the spatial arrangement of protein subunits and chromophores, crucial for deciphering the energy transfer mechanism. They reveal how the pentacylindrical core is formed, identify key interactions between linker proteins and the bilin chromophores, and indicate pathways for unidirectional energy transfer.

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Structure of the maize photosystem I supercomplex with light-harvesting complexes I and II

Science ◽

10.1126/science.aat1156 ◽

2018 ◽

Vol 360 (6393) ◽

pp. 1109-1113 ◽

Cited By ~ 48

Author(s):

Xiaowei Pan ◽

Jun Ma ◽

Xiaodong Su ◽

Peng Cao ◽

Wenrui Chang ◽

...

Keyword(s):

Electron Microscopy ◽

Energy Transfer ◽

Complex I ◽

Light Harvesting ◽

Light Conditions ◽

Light Harvesting Complexes ◽

Light Harvesting Complex ◽

Cryo Electron Microscopy ◽

Photosystems I And Ii ◽

Light Harvesting Complex Ii

Plants regulate photosynthetic light harvesting to maintain balanced energy flux into photosystems I and II (PSI and PSII). Under light conditions favoring PSII excitation, the PSII antenna, light-harvesting complex II (LHCII), is phosphorylated and forms a supercomplex with PSI core and the PSI antenna, light-harvesting complex I (LHCI). Both LHCI and LHCII then transfer excitation energy to the PSI core. We report the structure of maize PSI-LHCI-LHCII solved by cryo–electron microscopy, revealing the recognition site between LHCII and PSI. The PSI subunits PsaN and PsaO are observed at the PSI-LHCI interface and the PSI-LHCII interface, respectively. Each subunit relays excitation to PSI core through a pair of chlorophyll molecules, thus revealing previously unseen paths for energy transfer between the antennas and the PSI core.

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Plant and Algal PSII–LHCII Supercomplexes: Structure, Evolution and Energy Transfer

Plant and Cell Physiology ◽

10.1093/pcp/pcab072 ◽

2021 ◽

Author(s):

Xin Sheng ◽

Zhenfeng Liu ◽

Eunchul Kim ◽

Jun Minagawa

Keyword(s):

Energy Transfer ◽

Light Harvesting ◽

Chemical Form ◽

Structure Evolution ◽

Light Harvesting Complex ◽

Green Algal ◽

Cryo Electron Microscopy ◽

Light Harvesting Complex Ii ◽

Overall Efficiency ◽

Psii Subunits

Abstract Photosynthesis is the process conducted by plants and algae to capture photons and store their energy into a chemical form. The light-harvesting, excitation transfer, charge separation, and electron transfer in photosystem II (PSII) are the critical initial reactions of photosynthesis and thereby largely determine its overall efficiency. In this review, we outline the rapidly accumulating knowledges about the architectures and assemblies of plant and green algal PSII–light harvesting complex II (LHCII) supercomplexes with a particular focus on new insights provided by the recent high-resolution cryo-electron microscopy (cryo-EM) map of the supercomplexes from a green alga Chlamydomonas reinhardtii. We make pair-wise comparative analyses between the supercomplexes from plants and green algae to gain insights about the evolution of the PSII–LHCII supercomplexes involving the peripheral small PSII subunits that might have been acquired during the evolution, and about the energy transfer pathways that define their light-harvesting and photoprotective properties.

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Fluorescent Quantum Dots as Artificial Antennas for Enhanced Light Harvesting and Energy Transfer to Photosynthetic Reaction Centers

Angewandte Chemie ◽

10.1002/ange.201003067 ◽

2010 ◽

Vol 122 (40) ◽

pp. 7375-7379 ◽

Cited By ~ 6

Author(s):

Igor Nabiev ◽

Aliaksandra Rakovich ◽

Alyona Sukhanova ◽

Evgeniy Lukashev ◽

Vadim Zagidullin ◽

...

Keyword(s):

Quantum Dots ◽

Energy Transfer ◽

Light Harvesting ◽

Reaction Centers ◽

Photosynthetic Reaction Centers

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Fluorescent Quantum Dots as Artificial Antennas for Enhanced Light Harvesting and Energy Transfer to Photosynthetic Reaction Centers

Angewandte Chemie International Edition ◽

10.1002/anie.201003067 ◽

2010 ◽

Vol 49 (40) ◽

pp. 7217-7221 ◽

Cited By ~ 121

Author(s):

Igor Nabiev ◽

Aliaksandra Rakovich ◽

Alyona Sukhanova ◽

Evgeniy Lukashev ◽

Vadim Zagidullin ◽

...

Keyword(s):

Quantum Dots ◽

Energy Transfer ◽

Light Harvesting ◽

Reaction Centers ◽

Photosynthetic Reaction Centers

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Uphill energy transfer mechanism for photosynthesis in the Antarctic alga

10.21203/rs.3.rs-701485/v1 ◽

2021 ◽

Author(s):

Makiko Kosugi ◽

Masato Kawasaki ◽

Yutaka Shibata ◽

Kojiro Hara ◽

Shinichi Takaichi ◽

...

Keyword(s):

Energy Transfer ◽

Photosystem Ii ◽

Excitation Energy ◽

High Efficiency ◽

Light Harvesting ◽

Red Light ◽

Excitation Energy Transfer ◽

Energy Transfer Mechanism ◽

Light Harvesting Complex ◽

Prasiola Crispa

Abstract Prasiola crispa, a major green alga in Antarctica, forms layered colonies for survival under the severe terrestrial conditions of Antarctica, which include severe cold, drought, and strong sunlight. As a result of these conditions, the surface cells of P. crispa and other Antarctic organisms face high risk of photodamage. Cells of deeper layer escape from photodamage at the sacrifice of photosynthetic active radiation except infrared. P. crispa achieves effective photosynthesis by low energy far-red light for photosystem II excitation with high efficiency similar to that of visible light. Here, we identified a far-red light-harvesting complex of photosystem II in P. crispa, Pc-frLHC, and proposed a molecular mechanism of uphill excitation energy transfer based on its cryogenic electron-microscopy structure. While Pc-frLHC is associated with photosystem II, it is evolutionarily related to the light-harvesting complex of photosystem I. Pc-frLHC forms a ring-shaped homo-undecamer in which all chlorophyll a molecules are energetically connected and contains chlorophyll a trimers. It seems that the trimers are long-wavelength-absorbing chlorophylls for far-red light at 708 nm, and further absorbance extension is accomplished by Davydov-splitting in dimeric chlorophylls. The chlorophyll network should enable a highly efficient entropy-driven uphill excitation energy transfer using far-red light up to 725 nm.

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Structures of the Cyanobacterial Phycobilisome

10.1101/2021.11.15.468712 ◽

2021 ◽

Author(s):

Paul V Sauer ◽

Maria Agustina Dominguez-Martin ◽

Henning Kirst ◽

Markus Sutter ◽

David Bina ◽

...

Keyword(s):

Light Harvesting ◽

Model Organism ◽

Spectroscopic Properties ◽

Macromolecular Complex ◽

Photosynthetic Reaction Centers ◽

Molecular Architecture ◽

Synechocystis Pcc 6803 ◽

Cryo Electron Microscopy ◽

Harvesting Systems ◽

Pcc 6803

The phycobilisome is an elaborate antenna that is responsible for light-harvesting in cyanobacteria and red-algae. This large macromolecular complex captures incident sunlight and transfers the energy via a network of pigment molecules called bilins to the photosynthetic reaction centers. The phycobilisome of the model organism Synechocystis PCC 6803 consists of a core to which six rods are attached but its detailed molecular architecture and regulation in response to environmental conditions is not well understood. Here we present cryo-electron microscopy structures of the 6.2 MDa phycobilisome from Synechocystis PCC 6803 resolved at 2.1 Å (rods) to 2.7 Å (core), revealing three distinct conformations, two previously unknown. We found that two of the rods are mobile and can switch conformation within the complex, revealing a layer of regulation not described previously. In addition, we found a novel linker protein in the structure, that may represent a long-sought subunit that tethers the phycobilisome to the thylakoid membrane. Finally, we show how excitation energy is transferred within the phycobilisome and correlate our structures with known spectroscopic properties. Together, our results provide detailed insights into the biophysical underpinnings of cyanobacterial light harvesting and lay the foundation for bioengineering of future phycobilisome variants and artificial light harvesting systems.

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