Structure of photosystem I-LHCI-LHCII from the green alga Chlamydomonas reinhardtii in State 2

AbstractPhotosystem I (PSI) and II (PSII) balance their light energy distribution absorbed by their light-harvesting complexes (LHCs) through state transition to maintain the maximum photosynthetic performance and to avoid photodamage. In state 2, a part of LHCII moves to PSI, forming a PSI-LHCI-LHCII supercomplex. The green alga Chlamydomonas reinhardtii exhibits state transition to a far larger extent than higher plants. Here we report the cryo-electron microscopy structure of a PSI-LHCI-LHCII supercomplex in state 2 from C. reinhardtii at 3.42 Å resolution. The result reveals that the PSI-LHCI-LHCII of C. reinhardtii binds two LHCII trimers in addition to ten LHCI subunits. The PSI core subunits PsaO and PsaH, which were missed or not well-resolved in previous Cr-PSI-LHCI structures, are observed. The present results reveal the organization and assembly of PSI core subunits, LHCI and LHCII, pigment arrangement, and possible pathways of energy transfer from peripheral antennae to the PSI core.

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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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Structure of a C2S2M2N2-type PSII–LHCII supercomplex from the green alga Chlamydomonas reinhardtii

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1912462116 ◽

2019 ◽

Vol 116 (42) ◽

pp. 21246-21255 ◽

Cited By ~ 19

Author(s):

Liangliang Shen ◽

Zihui Huang ◽

Shenghai Chang ◽

Wenda Wang ◽

Jingfen Wang ◽

...

Keyword(s):

Energy Transfer ◽

Chlamydomonas Reinhardtii ◽

Green Alga ◽

Higher Plants ◽

Huge Number ◽

Higher Plant ◽

Low Light ◽

Green Algal ◽

Light Harvesting Antenna ◽

Energy Transfer Pathway

Photosystem II (PSII) in the thylakoid membranes of plants, algae, and cyanobacteria catalyzes light-induced oxidation of water by which light energy is converted to chemical energy and molecular oxygen is produced. In higher plants and most eukaryotic algae, the PSII core is surrounded by variable numbers of light-harvesting antenna complex II (LHCII), forming a PSII–LHCII supercomplex. In order to harvest energy efficiently at low–light-intensity conditions under water, a complete PSII–LHCII supercomplex (C2S2M2N2) of the green alga Chlamydomonas reinhardtii (Cr) contains more antenna subunits and pigments than the dominant PSII–LHCII supercomplex (C2S2M2) of plants. The detailed structure and energy transfer pathway of the Cr-PSII–LHCII remain unknown. Here we report a cryoelectron microscopy structure of a complete, C2S2M2N2-type PSII–LHCII supercomplex from C. reinhardtii at 3.37-Å resolution. The results show that the Cr-C2S2M2N2 supercomplex is organized as a dimer, with 3 LHCII trimers, 1 CP26, and 1 CP29 peripheral antenna subunits surrounding each PSII core. The N-LHCII trimer partially occupies the position of CP24, which is present in the higher-plant PSII–LHCII but absent in the green alga. The M trimer is rotated relative to the corresponding M trimer in plant PSII–LHCII. In addition, some unique features were found in the green algal PSII core. The arrangement of a huge number of pigments allowed us to deduce possible energy transfer pathways from the peripheral antennae to the PSII core.

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LHCSR1-dependent fluorescence quenching is mediated by excitation energy transfer from LHCII to photosystem I in Chlamydomonas reinhardtii

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1720574115 ◽

2018 ◽

Vol 115 (14) ◽

pp. 3722-3727 ◽

Cited By ~ 25

Author(s):

Kotaro Kosuge ◽

Ryutaro Tokutsu ◽

Eunchul Kim ◽

Seiji Akimoto ◽

Makio Yokono ◽

...

Keyword(s):

Energy Transfer ◽

Photosystem Ii ◽

Fluorescence Quenching ◽

Excitation Energy ◽

Chlamydomonas Reinhardtii ◽

Photosystem I ◽

Excitation Energy Transfer ◽

High Light ◽

Light Harvesting Complexes ◽

Photosynthetic Organisms

Photosynthetic organisms are frequently exposed to light intensities that surpass the photosynthetic electron transport capacity. Under these conditions, the excess absorbed energy can be transferred from excited chlorophyll in the triplet state (3Chl*) to molecular O2, which leads to the production of harmful reactive oxygen species. To avoid this photooxidative stress, photosynthetic organisms must respond to excess light. In the green alga Chlamydomonas reinhardtii, the fastest response to high light is nonphotochemical quenching, a process that allows safe dissipation of the excess energy as heat. The two proteins, UV-inducible LHCSR1 and blue light-inducible LHCSR3, appear to be responsible for this function. While the LHCSR3 protein has been intensively studied, the role of LHCSR1 has been only partially elucidated. To investigate the molecular functions of LHCSR1 in C. reinhardtii, we performed biochemical and spectroscopic experiments and found that the protein mediates excitation energy transfer from light-harvesting complexes for Photosystem II (LHCII) to Photosystem I (PSI), rather than Photosystem II, at a low pH. This altered excitation transfer allows remarkable fluorescence quenching under high light. Our findings suggest that there is a PSI-dependent photoprotection mechanism that is facilitated by LHCSR1.

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Faculty Opinions recommendation of Identification and characterization of an assembly intermediate subcomplex of photosystem I in the green alga Chlamydomonas reinhardtii.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.3256956.2952058 ◽

2010 ◽

Author(s):

Nathan Nelson ◽

Alexey Amunts

Keyword(s):

Chlamydomonas Reinhardtii ◽

Green Alga ◽

Photosystem I ◽

Assembly Intermediate ◽

Identification And Characterization

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Primary Charge Separation and Energy Transfer in the Photosystem I Reaction Center of Higher Plants

The Journal of Physical Chemistry ◽

10.1021/jp9604709 ◽

1996 ◽

Vol 100 (29) ◽

pp. 12086-12099 ◽

Cited By ~ 37

Author(s):

Nigel T. H. White ◽

Godfrey S. Beddard ◽

Jonathan R. G. Thorne ◽

Tim M. Feehan ◽

Tia E. Keyes ◽

...

Keyword(s):

Energy Transfer ◽

Reaction Center ◽

Photosystem I ◽

Charge Separation ◽

Higher Plants ◽

Primary Charge Separation

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Chlorophyll triplet states associated with Photosystem I and Photosystem II in thylakoids of the green alga Chlamydomonas reinhardtii

Biochimica et Biophysica Acta (BBA) - Bioenergetics ◽

10.1016/j.bbabio.2006.10.007 ◽

2007 ◽

Vol 1767 (1) ◽

pp. 88-105 ◽

Cited By ~ 26

Author(s):

Stefano Santabarbara ◽

Giancarlo Agostini ◽

Anna Paola Casazza ◽

Christopher D. Syme ◽

P. Heathcote ◽

...

Keyword(s):

Photosystem Ii ◽

Chlamydomonas Reinhardtii ◽

Green Alga ◽

Photosystem I ◽

Triplet States

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Isolation and characterization of three membranebound chlorophyll-protein complexes from four dinoflagellate species

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.1993.0080 ◽

1993 ◽

Vol 340 (1294) ◽

pp. 381-392 ◽

Cited By ~ 31

Keyword(s):

Energy Transfer ◽

Photosystem I ◽

Light Harvesting ◽

Protein Complexes ◽

Gradient Centrifugation ◽

Water Soluble ◽

Molar Ratio ◽

Light Harvesting Complexes ◽

Light Harvesting Complex ◽

Isolation And Characterization

Employing discontinuous sucrose density gradient centrifugation of n -dodecyl β-d-maltoside-solubilized thylakoid membranes, three chlorophyll (Chl)-protein complexes containing Chl a , Chl c 2 and peridinin in different proportions, were isolated from the dinoflagellates Symbiodinium microadriaticum, S. kawagutii, S. pilosum and Heterocapsa pygmaea . In S. microadriaticum , the first complex, containing 13% of the total cellular Chl a , and minor quantities of Chl c 2 and peridinin, is associated with polypeptides with apparent molecular mass ( M r ) of 8-9 kDa, and demonstrated inefficient energy transfer from the accessory pigments to Chl a . The second complex contains Chl a , Chl c 2 and peridinin in a molar ratio of 1:1:2, associated with two apoproteins of M r 19-20 kDa, and comprises 45%, 75% and 70%, respectively, of the cellular Chl a , Chl c 2 and peridinin. The efficient energy transfer from Chl c 2 and peridinin to Chl a in this complex is supportive of a light-harvesting function. This Chl a - c 2 - peridin-protein complex represents the major light-harvesting complex in dinoflagellates. The third complex obtained contains 12% of the cellular Chl a , and appears to be the core of photosystem I, associated with a light-harvesting complex. This complex is spectroscopically similar to analogous preparations from different taxonomic groups, but demonstrates a unique apoprotein composition. Antibodies against the water-soluble peridinin-Chl a -protein (sPCP) light-harvesting complexes failed to cross-react with any of the thylakoid-associated complexes, as did antibodies against Chl a - c -fucoxanthin apoprotein (from diatoms). Antibodies against the P 700 apoprotein of plants did not cross-react with the photosystem I complex. Similar results were observed in the other dinoflagellates.

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