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Liu R, Zhen ZH, Li W, Ge B, Qin S. How can Phycobilisome, the unique light harvesting system in certain algae working highly efficiently: The connection in between structures and functions. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2024; 186:39-52. [PMID: 38030044 DOI: 10.1016/j.pbiomolbio.2023.11.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 11/02/2023] [Accepted: 11/23/2023] [Indexed: 12/01/2023]
Abstract
Algae, which are ubiquitous in ecosystems, have evolved a variety of light-harvesting complexes to better adapt to diverse habitats. Phycobilisomes/phycobiliproteins, unique to cyanobacteria, red algae, and certain cryptomonads, compensate for the lack of chlorophyll absorption, allowing algae to capture and efficiently transfer light energy in aquatic environments. With the advancement of microscopy and spectroscopy, the structure and energy transfer processes of increasingly complex phycobilisomes have been elucidated, providing us with a vivid portrait of the dynamic adaptation of their structures to the light environment in which algae thrive: 1) Cyanobacteria living on the surface of the water use short, small phycobilisomes to absorb red-orange light and reduce the damage from blue-violet light via multiple methods; 2) Large red algae inhabiting the depths of the ocean have evolved long and dense phycobilisomes containing phycoerythrin to capture the feeble blue-green light; 3) In far-red light environments such as caves, algae use special allophycocyanin cores to optimally utilize the far-red light; 4) When the environment shifts, algae can adjust the length, composition and density of their rods to better adapt; 5) By carefully designing the position of the pigments, phycobilisomes can transfer light energy to the reaction center with nearly 100% efficiency via three energy transfer processes.
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Affiliation(s)
- Runze Liu
- Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, Shandong, 264003, China; University of Chinese Academy of Sciences, Beijing, 100000, China
| | - Zhang-He Zhen
- Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Wenjun Li
- Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, Shandong, 264003, China
| | - Baosheng Ge
- China University of Petroleum (HUADONG), Qingdao, Shandong, 266580, China
| | - Song Qin
- Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, Shandong, 264003, China.
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2
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Voerman SE, Ruseckas A, Turnbull GA, Samuel IDW, Burdett HL. Red algae acclimate to low light by modifying phycobilisome composition to maintain efficient light harvesting. BMC Biol 2022; 20:291. [PMID: 36575464 PMCID: PMC9794408 DOI: 10.1186/s12915-022-01480-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 11/24/2022] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND Despite a global prevalence of photosynthetic organisms in the ocean's mesophotic zone (30-200+ m depth), the mechanisms that enable photosynthesis to proceed in this low light environment are poorly defined. Red coralline algae are the deepest known marine benthic macroalgae - here we investigated the light harvesting mechanism and mesophotic acclimatory response of the red coralline alga Lithothamnion glaciale. RESULTS Following initial absorption by phycourobilin and phycoerythrobilin in phycoerythrin, energy was transferred from the phycobilisome to photosystems I and II within 120 ps. This enabled delivery of 94% of excitations to reaction centres. Low light intensity, and to a lesser extent a mesophotic spectrum, caused significant acclimatory change in chromophores and biliproteins, including a 10% increase in phycoerythrin light harvesting capacity and a 20% reduction in chlorophyll-a concentration and photon requirements for photosystems I and II. The rate of energy transfer remained consistent across experimental treatments, indicating an acclimatory response that maintains energy transfer. CONCLUSIONS Our results demonstrate that responsive light harvesting by phycobilisomes and photosystem functional acclimation are key to red algal success in the mesophotic zone.
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Affiliation(s)
- Sofie E. Voerman
- Lyell Centre for Earth and Marine Science and Technology, Edinburgh, EH14 4BA UK ,grid.9531.e0000000106567444School of Energy, Geoscience, Infrastructure and Society, Heriot-Watt University, Edinburgh, EH14 4AS UK
| | - Arvydas Ruseckas
- grid.11914.3c0000 0001 0721 1626Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS UK
| | - Graham A. Turnbull
- grid.11914.3c0000 0001 0721 1626Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS UK
| | - Ifor D. W. Samuel
- grid.11914.3c0000 0001 0721 1626Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS UK
| | - Heidi L. Burdett
- Lyell Centre for Earth and Marine Science and Technology, Edinburgh, EH14 4BA UK ,grid.9531.e0000000106567444School of Energy, Geoscience, Infrastructure and Society, Heriot-Watt University, Edinburgh, EH14 4AS UK ,grid.12650.300000 0001 1034 3451Present Address: Department of Ecology and Environmental Sciences, Umeå University, Umeå, Sweden ,grid.12650.300000 0001 1034 3451Umeå Marine Sciences Centre, Umeå University, Norrbyn, Sweden
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3
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Pinevich AV, Averina SG. On the Edge of the Rainbow: Red-Shifted Chlorophylls and Far-Red Light Photoadaptation in Cyanobacteria. Microbiology (Reading) 2022. [DOI: 10.1134/s0026261722602019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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4
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Core and rod structures of a thermophilic cyanobacterial light-harvesting phycobilisome. Nat Commun 2022; 13:3389. [PMID: 35715389 PMCID: PMC9205905 DOI: 10.1038/s41467-022-30962-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 05/24/2022] [Indexed: 11/21/2022] Open
Abstract
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. Phycobilisome (PBS) absorbs solar energy and transfer the energy to photosynthetic membrane proteins. In this study, the structures of the pentacylindrical core and rod in PBS from a thermophilic cyanobacterium by cryo-electron microscopy.
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5
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Navotnaya P, Sohoni S, Lloyd LT, Abdulhadi SM, Ting PC, Higgins JS, Engel GS. Annihilation of Excess Excitations along Phycocyanin Rods Precedes Downhill Flow to Allophycocyanin Cores in the Phycobilisome of Synechococcus elongatus PCC 7942. J Phys Chem B 2022; 126:23-29. [PMID: 34982932 PMCID: PMC8762654 DOI: 10.1021/acs.jpcb.1c06509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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Cyanobacterial phycobilisome
complexes absorb visible sunlight
and funnel photogenerated excitons to the photosystems where charge
separation occurs. In the phycobilisome complex of Synechococcus
elongatus PCC 7942, phycocyanin protein rods that absorb
bluer wavelengths are assembled on allophycocyanin cores that absorb
redder wavelengths. This arrangement creates a natural energy gradient
toward the reaction centers of the photosystems. Here, we employ broadband
pump–probe spectroscopy to observe the fate of excess excitations
in the phycobilisome complex of this organism. We show that excess
excitons are quenched through exciton–exciton annihilation
along the phycocyanin rods prior to transfer to the allophycocyanin
cores. Our observations are especially relevant in comparison to other
antenna proteins, where exciton annihilation primarily occurs in the
lowest-energy chlorophylls. The observed effect could play a limited
photoprotective role in physiological light fluences. The exciton
decay dynamics is faster in the intact phycobilisome than in isolated
C-phycocyanin trimers studied in earlier work, confirming that this
effect is an emergent property of the complex assembly. Using the
obtained annihilation data, we calculate exciton hopping times of
2.2–6.4 ps in the phycocyanin rods. This value agrees with
earlier FRET calculations of exciton hopping times along phycocyanin
hexamers by Sauer and Scheer.
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Affiliation(s)
- Polina Navotnaya
- Department of Chemistry, James Franck Institute and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Siddhartha Sohoni
- Department of Chemistry, James Franck Institute and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Lawson T Lloyd
- Department of Chemistry, James Franck Institute and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Sami M Abdulhadi
- Department of Chemistry, James Franck Institute and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Po-Chieh Ting
- Department of Chemistry, James Franck Institute and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Jacob S Higgins
- Department of Chemistry, James Franck Institute and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Gregory S Engel
- Department of Chemistry, James Franck Institute and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
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6
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Li M, Ma J, Li X, Sui SF. In situ cryo-ET structure of phycobilisome-photosystem II supercomplex from red alga. eLife 2021; 10:e69635. [PMID: 34515634 PMCID: PMC8437437 DOI: 10.7554/elife.69635] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Accepted: 08/19/2021] [Indexed: 11/13/2022] Open
Abstract
Phycobilisome (PBS) is the main light-harvesting antenna in cyanobacteria and red algae. How PBS transfers the light energy to photosystem II (PSII) remains to be elucidated. Here we report the in situ structure of the PBS-PSII supercomplex from Porphyridium purpureum UTEX 2757 using cryo-electron tomography and subtomogram averaging. Our work reveals the organized network of hemiellipsoidal PBS with PSII on the thylakoid membrane in the native cellular environment. In the PBS-PSII supercomplex, each PBS interacts with six PSII monomers, of which four directly bind to the PBS, and two bind indirectly. Additional three 'connector' proteins also contribute to the connections between PBS and PSIIs. Two PsbO subunits from adjacent PSII dimers bind with each other, which may promote stabilization of the PBS-PSII supercomplex. By analyzing the interaction interface between PBS and PSII, we reveal that αLCM and ApcD connect with CP43 of PSII monomer and that αLCM also interacts with CP47' of the neighboring PSII monomer, suggesting the multiple light energy delivery pathways. The in situ structures illustrate the coupling pattern of PBS and PSII and the arrangement of the PBS-PSII supercomplex on the thylakoid, providing the near-native 3D structural information of the various energy transfer from PBS to PSII.
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Affiliation(s)
- Meijing Li
- Key Laboratory for Protein Sciences of Ministry of Education, Beijing Advanced Innovation Center for Structural Biology & Frontier Research Center for Biological Structure, School of Life Sciences, Tsinghua UniversityBeijingChina
| | - Jianfei Ma
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology & Frontier Research Center for Biological Structure, School of Life Sciences, Tsinghua UniversityBeijingChina
| | - Xueming Li
- Key Laboratory for Protein Sciences of Ministry of Education, Beijing Advanced Innovation Center for Structural Biology & Frontier Research Center for Biological Structure, School of Life Sciences, Tsinghua UniversityBeijingChina
| | - Sen-Fang Sui
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology & Frontier Research Center for Biological Structure, School of Life Sciences, Tsinghua UniversityBeijingChina
- Department of Biology, Southern University of Science and TechnologyGuangdongChina
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7
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Noji T, Watanabe M, Dewa T, Itoh S, Ikeuchi M. Direct Energy Transfer from Allophycocyanin-Free Rod-Type CpcL-Phycobilisome to Photosystem I. J Phys Chem Lett 2021; 12:6692-6697. [PMID: 34260249 DOI: 10.1021/acs.jpclett.1c01763] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Phycobilisomes (PBSs) are photosynthetic antenna megacomplexes comprising pigment-binding proteins (cores and rods) joined with linker proteins. A rod-type PBS that does not have a core is connected to photosystem I (PSI) by a CpcL linker protein, which stabilizes a red-form of the phycocyanobilin (red-PCB) in the rod. However, quantitative information on the energy transfer from red-type PBS to PSI has not been determined. Herein, the isolated supercomplex of the rod-type PBS and the PSI tetramer from Anabaena sp. PCC 7120 were probed by time-resolved spectroscopy at 77 K and by decay-associated spectral analysis to show that red-PCB mediates the fast and efficient (time constant = 90 ps, efficiency = 95%) transfer of excitation energy from PCB to chlorophyll a (Chl a). According to the Förster energy transfer mechanism, this high efficiency corresponds to a 4 nm distance between red-PCB and Chl a, suggesting that β-84 PCB in the rod acts as red-PCB.
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Affiliation(s)
- Tomoyasu Noji
- Department of Life Science and Applied Chemistry, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan
| | - Mai Watanabe
- Department of Life Sciences (Biology), Graduate School of Arts and Sciences, University of Tokyo, Komaba, Meguro, Tokyo 153-8902, Japan
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama 332-0012, Japan
| | - Takehisa Dewa
- Department of Life Science and Applied Chemistry, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan
| | - Shigeru Itoh
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
| | - Masahiko Ikeuchi
- Department of Life Sciences (Biology), Graduate School of Arts and Sciences, University of Tokyo, Komaba, Meguro, Tokyo 153-8902, Japan
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama 332-0012, Japan
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8
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Hirota Y, Serikawa H, Kawakami K, Ueno M, Kamiya N, Kosumi D. Ultrafast energy transfer dynamics of phycobilisome from Thermosynechococcus vulcanus, as revealed by ps fluorescence and fs pump-probe spectroscopies. PHOTOSYNTHESIS RESEARCH 2021; 148:181-190. [PMID: 33997927 DOI: 10.1007/s11120-021-00844-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 05/04/2021] [Indexed: 06/12/2023]
Abstract
Cyanobacterial photosynthetic systems efficiently capture sunlight using the pigment-protein megacomplexes, phycobilisome (PBS). The energy is subsequently transferred to photosystem I (PSI) and II (PSII), to produce electrochemical potentials. In the present study, we performed picosecond (ps) time-resolved fluorescence and femtosecond (fs) pump-probe spectroscopies on the intact PBS from a thermophilic cyanobacterium, Thermosynechococcus vulcanus, to reveal excitation energy transfer dynamics in PBS. The photophysical properties of the intact PBS were well characterized by spectroscopic measurements covering wide temporal range from femtoseconds to nanoseconds. The ps fluorescence measurements excited at 570 nm, corresponding to the higher energy of the phycocyanin (PC) absorption band, demonstrated the excitation energy transfer from the PC rods to the allophycocyanin (APC) core complex as well as the energy transfer in the APC core complex. Then, the fs pump-probe measurements revealed the detailed energy transfer dynamics in the PC rods taking place in an ultrafast time scale. The results obtained in this study provide the full picture of the funnel-type excitation energy transfer with rate constants of (0.57 ps)-1 → (7.3 ps)-1 → (53 ps)-1 → (180 ps)-1 → (1800 ps)-1.
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Affiliation(s)
- Yuma Hirota
- Department of Physics, Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan
| | - Hiroki Serikawa
- Department of Physics, Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan
| | - Keisuke Kawakami
- Biostructual Mechanism Laboratory, RIKEN Spring-8 Center, 1-1-1, Sayo, Kouto, Hyougo, 679-5148, Japan.
| | - Masato Ueno
- Department of Physics, Faculty of Science, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan
| | - Nobuo Kamiya
- The OCU Research Center for Artificial Photosynthesis, Osaka City University, 3-3-138, Sugimoto, Sumiyoshi-ku, Osaka, 558-8585, Japan
| | - Daisuke Kosumi
- Institute of Industrial Nanomaterials, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan.
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9
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Kikuchi H. Functional roles of the hexamer structure of C-phycocyanin revealed by calculation of absorption wavelength. FEBS Open Bio 2021; 11:164-172. [PMID: 33190413 PMCID: PMC7780113 DOI: 10.1002/2211-5463.13038] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 10/27/2020] [Accepted: 11/11/2020] [Indexed: 11/11/2022] Open
Abstract
Cyanophyta-phycocyanin (C-PC) is the main constituent of the rod of phycobilisome (PBS), which is a highly ordered and large peripheral light-harvesting protein complex present on the cytoplasmic side of the thylakoid membrane in cyanobacteria and red algae. The C-PC monomer comprises two chains, α- and β-subunits, and aggregates to form ring-shaped trimers (αβ)3 with rotational symmetry. The ring-shaped trimer (αβ)3 is a structural block unit (SBU) that forms the rod of PBS. Two (αβ)3 SBUs are arranged in a face-to-face manner to form an (αβ)6 -hexamer. In this study, the electronic states of three phycocyanobilins, α84, β84, and β155 in C-phycocyanin, constituting the rod of the PBS, were calculated for both the trimer and hexamer models by considering the effect of the electrostatic field of protein moieties and water molecules. For the hexamer, the absorption wavelengths of α84, β84, and β155 were similar to those obtained experimentally; however, for the trimer, only the absorption wavelength of β155 shifted toward a shorter-wavelength. The nature of the hexamer structure as a hierarchical structure is revealed by considering the calculated absorption wavelength and energy transfer.
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Affiliation(s)
- Hiroto Kikuchi
- Department of PhysicsNippon Medical SchoolMusashinoJapan
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Investigations of the Energy Transfer in the Phycobilisome Antenna of Arthrospira platensis Using Femtosecond Spectroscopy. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10114045] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Understanding the energy transfer in phycobilisomes extracted from cyanobacteria can be used for building biomimetic hybrid systems for optimized solar energy collection and photocurrent amplification. In this paper, we applied time-resolved absorption and fluorescence spectroscopy to investigate the ultrafast dynamics in a hemidiscoidal phycobilisome obtained from Arthrospira platensis. We obtained the steady-state and time-resolved optical properties and identified the possible pathways of the excitation energy transfer in the phycobilisome and its components, phycocyanin and allophycocyanin. The transient absorption data were studied using global analysis and revealed the existence of ultrafast kinetics down to 850 fs in the phycobilisome. The fluorescence lifetimes in the nanosecond time-scale assigned to the final emitters in each sample were obtained from the time-correlated single photon counting fluorescence experiments.
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Adir N, Bar-Zvi S, Harris D. The amazing phycobilisome. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2019; 1861:148047. [PMID: 31306623 DOI: 10.1016/j.bbabio.2019.07.002] [Citation(s) in RCA: 74] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2019] [Revised: 06/19/2019] [Accepted: 07/09/2019] [Indexed: 10/26/2022]
Abstract
Cyanobacteria and red-algae share a common light-harvesting complex which is different than all other complexes that serve as photosynthetic antennas - the Phycobilisome (PBS). The PBS is found attached to the stromal side of thylakoid membranes, filling up most of the gap between individual thylakoids. The PBS self assembles from similar homologous protein units that are soluble and contain conserved cysteine residues that covalently bind the light absorbing chromophores, linear tetra-pyrroles. Using similar construction principles, the PBS can be as large as 16.8 MDa (68×45×39nm), as small as 1.2 MDa (24 × 11.5 × 11.5 nm), and in some unique cases smaller still. The PBS can absorb light between 450 nm to 650 nm and in some cases beyond 700 nm, depending on the species, its composition and assembly. In this review, we will present new observations and structures that expand our understanding of the distinctive properties that make the PBS an amazing light harvesting system. At the end we will suggest why the PBS, for all of its excellent properties, was discarded by photosynthetic organisms that arose later in evolution such as green algae and higher plants.
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Affiliation(s)
- Noam Adir
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 32000, Israel.
| | - Shira Bar-Zvi
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | - Dvir Harris
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 32000, Israel
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12
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Niedzwiedzki DM, Liu H, Blankenship RE. Excitation Energy Transfer in Intact CpcL-Phycobilisomes from Synechocystis sp. PCC 6803. J Phys Chem B 2019; 123:4695-4704. [PMID: 31042029 DOI: 10.1021/acs.jpcb.9b02696] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This work highlights spectroscopic studies performed on a CpcL-phycobilisome (CpcL-PBS) light-harvesting complex from cyanobacterium Synechocystis sp. PCC 6803 ΔAB strain. The CpcL-PBS antenna has the form of a single rod made up exclusively of phycocyanins (PCs), a structure that is much simpler compared to the better known and broadly studied CpcG-PBS that consists of a cylindrical core with a set of protruding PC rods. Steady-state and time-resolved fluorescence studies demonstrated that the CpcL-PBS antenna comprises two spectral forms of phycocyanobilin (PCB), one emitting at 650 nm and a second emitting at 670 nm. The latter one presumably serves as the so-called terminal energy emitter without allophycocyanin. Studies of excitation energy migration between those two PCB forms demonstrated that even small buffer alterations, commonly applied by spectroscopists to tweak buffers to be more friendly for a certain type of spectroscopy, may lead to very different experimental outcomes and, in consequence, to differences in models of excitation migration pathway in this antenna complex.
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