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Kim RG, Huang W, Findinier J, Bunbury F, Redekop P, Shrestha R, Grismer TS, Vilarrasa-Blasi J, Jinkerson RE, Fakhimi N, Fauser F, Jonikas MC, Onishi M, Xu SL, Grossman AR. Chloroplast Methyltransferase Homolog RMT2 is Involved in Photosystem I Biogenesis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.12.21.572672. [PMID: 38187728 PMCID: PMC10769443 DOI: 10.1101/2023.12.21.572672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
Oxygen (O2), a dominant element in the atmosphere and essential for most life on Earth, is produced by the photosynthetic oxidation of water. However, metabolic activity can cause accumulation of reactive O2 species (ROS) and severe cell damage. To identify and characterize mechanisms enabling cells to cope with ROS, we performed a high-throughput O2 sensitivity screen on a genome-wide insertional mutant library of the unicellular alga Chlamydomonas reinhardtii. This screen led to identification of a gene encoding a protein designated Rubisco methyltransferase 2 (RMT2). Although homologous to methyltransferases, RMT2 has not been experimentally demonstrated to have methyltransferase activity. Furthermore, the rmt2 mutant was not compromised for Rubisco (first enzyme of Calvin-Benson Cycle) levels but did exhibit a marked decrease in accumulation/activity of photosystem I (PSI), which causes light sensitivity, with much less of an impact on other photosynthetic complexes. This mutant also shows increased accumulation of Ycf3 and Ycf4, proteins critical for PSI assembly. Rescue of the mutant phenotype with a wild-type (WT) copy of RMT2 fused to the mNeonGreen fluorophore indicates that the protein localizes to the chloroplast and appears to be enriched in/around the pyrenoid, an intrachloroplast compartment present in many algae that is packed with Rubisco and potentially hypoxic. These results indicate that RMT2 serves an important role in PSI biogenesis which, although still speculative, may be enriched around or within the pyrenoid.
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Affiliation(s)
- Rick G. Kim
- Department of Biosphere Science and Engineering, Carnegie Institution for Science, Stanford, CA 94305, USA
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Weichao Huang
- Department of Biosphere Science and Engineering, Carnegie Institution for Science, Stanford, CA 94305, USA
| | - Justin Findinier
- Department of Biosphere Science and Engineering, Carnegie Institution for Science, Stanford, CA 94305, USA
| | - Freddy Bunbury
- Department of Biosphere Science and Engineering, Carnegie Institution for Science, Stanford, CA 94305, USA
| | - Petra Redekop
- Department of Biosphere Science and Engineering, Carnegie Institution for Science, Stanford, CA 94305, USA
| | - Ruben Shrestha
- Department of Biosphere Science and Engineering, Carnegie Institution for Science, Stanford, CA 94305, USA
| | - TaraBryn S Grismer
- Department of Biosphere Science and Engineering, Carnegie Institution for Science, Stanford, CA 94305, USA
| | | | - Robert E. Jinkerson
- Department of Chemical and Environmental Engineering, University of California, Riverside, CA 92521, USA
| | - Neda Fakhimi
- Department of Biosphere Science and Engineering, Carnegie Institution for Science, Stanford, CA 94305, USA
| | - Friedrich Fauser
- Department of Biosphere Science and Engineering, Carnegie Institution for Science, Stanford, CA 94305, USA
| | - Martin C. Jonikas
- Department of Molecular Biology, Princeton University, Princeton, NJ 08540, USA
| | - Masayuki Onishi
- Department of Biology, Duke University, Durham, NC 27708, USA
| | - Shou-Ling Xu
- Department of Biosphere Science and Engineering, Carnegie Institution for Science, Stanford, CA 94305, USA
| | - Arthur R. Grossman
- Department of Biosphere Science and Engineering, Carnegie Institution for Science, Stanford, CA 94305, USA
- Department of Biology, Stanford University, Stanford, CA 94305, USA
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Kozuleva MA, Ivanov BN. Superoxide Anion Radical Generation in Photosynthetic Electron Transport Chain. BIOCHEMISTRY. BIOKHIMIIA 2023; 88:1045-1060. [PMID: 37758306 DOI: 10.1134/s0006297923080011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 06/16/2023] [Accepted: 06/18/2023] [Indexed: 10/03/2023]
Abstract
This review analyzes data available in the literature on the rates, characteristics, and mechanisms of oxygen reduction to a superoxide anion radical at the sites of photosynthetic electron transport chain where this reduction has been established. The existing assumptions about the role of the components of these sites in this process are critically examined using thermodynamic approaches and results of the recent studies. The process of O2 reduction at the acceptor side of PSI, which is considered the main site of this process taking place in the photosynthetic chain, is described in detail. Evolution of photosynthetic apparatus in the context of controlling the leakage of electrons to O2 is explored. The reasons limiting application of the results obtained with the isolated segments of the photosynthetic chain to estimate the rates of O2 reduction at the corresponding sites in the intact thylakoid membrane are discussed.
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Affiliation(s)
- Marina A Kozuleva
- Institute of Basic Biological Problems, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
| | - Boris N Ivanov
- Institute of Basic Biological Problems, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
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Devadasu E, Kanna SD, Neelam S, Yadav RM, Nama S, Akhtar P, Polgár TF, Ughy B, Garab G, Lambrev PH, Subramanyam R. Long- and short-term acclimation of the photosynthetic apparatus to salinity in Chlamydomonas reinhardtii. The role of Stt7 protein kinase. FRONTIERS IN PLANT SCIENCE 2023; 14:1051711. [PMID: 37089643 PMCID: PMC10113551 DOI: 10.3389/fpls.2023.1051711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Accepted: 03/03/2023] [Indexed: 05/03/2023]
Abstract
Salt stress triggers an Stt7-mediated LHCII-phosphorylation signaling mechanism similar to light-induced state transitions. However, phosphorylated LHCII, after detaching from PSII, does not attach to PSI but self-aggregates instead. Salt is a major stress factor in the growth of algae and plants. Here, our study mainly focuses on the organization of the photosynthetic apparatus to the long-term responses of Chlamydomonas reinhardtii to elevated NaCl concentrations. We analyzed the physiological effects of salt treatment at a cellular, membrane, and protein level by microscopy, protein profile analyses, transcripts, circular dichroism spectroscopy, chlorophyll fluorescence transients, and steady-state and time-resolved fluorescence spectroscopy. We have ascertained that cells that were grown in high-salinity medium form palmelloids sphere-shaped colonies, where daughter cells with curtailed flagella are enclosed within the mother cell walls. Palmelloid formation depends on the presence of a cell wall, as it was not observed in a cell-wall-less mutant CC-503. Using the stt7 mutant cells, we show Stt7 kinase-dependent phosphorylation of light-harvesting complex II (LHCII) in both short- and long-term treatments of various NaCl concentrations-demonstrating NaCl-induced state transitions that are similar to light-induced state transitions. The grana thylakoids were less appressed (with higher repeat distances), and cells grown in 150 mM NaCl showed disordered structures that formed diffuse boundaries with the flanking stroma lamellae. PSII core proteins were more prone to damage than PSI. At high salt concentrations (100-150 mM), LHCII aggregates accumulated in the thylakoid membranes. Low-temperature and time-resolved fluorescence spectroscopy indicated that the stt7 mutant was more sensitive to salt stress, suggesting that LHCII phosphorylation has a role in the acclimation and protection of the photosynthetic apparatus.
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Affiliation(s)
- Elsinraju Devadasu
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Sai Divya Kanna
- Institute of Plant Biology, Biological Research Centre, Eötvös Loránd Research Network, Szeged, Hungary
- Doctoral School of Biology, University of Szeged, Szeged, Hungary
| | - Satyabala Neelam
- Department of Biochemistry, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Ranay Mohan Yadav
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Srilatha Nama
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Parveen Akhtar
- Institute of Plant Biology, Biological Research Centre, Eötvös Loránd Research Network, Szeged, Hungary
| | - Tamás F. Polgár
- Institute of Biophysics, Biological Research Centre, Eötvös Loránd Research Network, Szeged, Hungary
- Theoretical Medicine Doctoral School, University of Szeged, Szeged, Hungary
| | - Bettina Ughy
- Institute of Plant Biology, Biological Research Centre, Eötvös Loránd Research Network, Szeged, Hungary
| | - Győző Garab
- Institute of Plant Biology, Biological Research Centre, Eötvös Loránd Research Network, Szeged, Hungary
- Department of Physics, Faculty of Science, University of Ostrava, Ostrava, Czechia
| | - Petar H. Lambrev
- Institute of Plant Biology, Biological Research Centre, Eötvös Loránd Research Network, Szeged, Hungary
| | - Rajagopal Subramanyam
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India
- *Correspondence: Rajagopal Subramanyam,
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Wang S, Wufuer R, Duo J, Li W, Pan X. Cadmium Caused Different Toxicity to Photosystem I and Photosystem II of Freshwater Unicellular Algae Chlorella pyrenoidosa (Chlorophyta). TOXICS 2022; 10:toxics10070352. [PMID: 35878257 PMCID: PMC9323598 DOI: 10.3390/toxics10070352] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 06/21/2022] [Accepted: 06/23/2022] [Indexed: 01/07/2023]
Abstract
Heavy metals such as Cd pose environmental problems and threats to a variety of organisms. The effects of cadmium (Cd) on the growth and activities of photosystem I (PSI) and photosystem II (PSII) of Chlorella pyrenoidosa were studied. The growth rate of cells treated with 25 and 100 µM of Cd for longer than 48 h were significantly lower than the control, accompanying with the inhibition of photosynthesis. The result of quantum yields and electron transport rates (ETRs) in PSI and PSII showed that Cd had a more serious inhibition on PSII than on PSI. Cd decreased the efficiency of PSII to use the energy under high light with increasing Cd concentration. In contrast, the quantum yield of PSI did not show a significant difference among different Cd treatments. The activation of cyclic electron flow (CEF) and the inhibition of linear electron flow (LEF) due to Cd treatment were observed. The photochemical quantum yield of PSI and the tolerance of ETR of PSI to Cd treatments were due to the activation of CEF around PSI. The activation of CEF also played an important role in induction of non-photochemical quenching (NPQ). The binding features of Cd ions and photosystem particles showed that Cd was easier to combine with PSII than PSI, which may explain the different toxicity of Cd on PSII and PSI.
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Affiliation(s)
- Shuzhi Wang
- National Engineering Technology Research Center for Desert-Oasis Ecological Construction, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, 818 South Beijing Road, Urumqi 830011, China; (S.W.); (R.W.); (J.D.)
- Xinjiang Key Laboratory of Environmental Pollution and Bioremediation, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China
| | - Rehemanjiang Wufuer
- National Engineering Technology Research Center for Desert-Oasis Ecological Construction, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, 818 South Beijing Road, Urumqi 830011, China; (S.W.); (R.W.); (J.D.)
- Xinjiang Key Laboratory of Environmental Pollution and Bioremediation, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China
| | - Jia Duo
- National Engineering Technology Research Center for Desert-Oasis Ecological Construction, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, 818 South Beijing Road, Urumqi 830011, China; (S.W.); (R.W.); (J.D.)
- Xinjiang Key Laboratory of Environmental Pollution and Bioremediation, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China
| | - Wenfeng Li
- National Engineering Technology Research Center for Desert-Oasis Ecological Construction, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, 818 South Beijing Road, Urumqi 830011, China; (S.W.); (R.W.); (J.D.)
- Xinjiang Key Laboratory of Environmental Pollution and Bioremediation, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China
- Correspondence: (W.L.); (X.P.); Tel.: +86-991-7823-147 (W.L.)
| | - Xiangliang Pan
- Xinjiang Key Laboratory of Environmental Pollution and Bioremediation, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China
- Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou 310014, China
- Correspondence: (W.L.); (X.P.); Tel.: +86-991-7823-147 (W.L.)
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Szewczyk S, Goyal A, Abram M, Burdziński G, Kargul J, Gibasiewicz K. Electron Transfer in a Bio-Photoelectrode Based on Photosystem I Multilayer Immobilized on the Conducting Glass. Int J Mol Sci 2022; 23:ijms23094774. [PMID: 35563164 PMCID: PMC9100268 DOI: 10.3390/ijms23094774] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2022] [Revised: 04/13/2022] [Accepted: 04/18/2022] [Indexed: 02/07/2023] Open
Abstract
A film of ~40 layers of partially oriented photosystem I (PSI) complexes isolated from the red alga Cyanidioschyzon merolae formed on the conducting glass through electrodeposition was investigated by time-resolved absorption spectroscopy and chronoamperometry. The experiments were performed at a range of electric potentials applied to the film and at different compositions of electrolyte solution being in contact with the film. The amount of immobilized proteins supporting light-induced charge separation (active PSI) ranged from ~10%, in the absence of any reducing agents (redox compounds or low potential), to ~20% when ascorbate and 2,6-dichlorophenolindophenol were added, and to ~35% when the high negative potential was additionally applied. The origin of the large fraction of permanently inactive PSI (65–90%) was unclear. Both reducing agents increased the subpopulation of active PSI complexes, with the neutral P700 primary electron donor, by reducing significant fractions of the photo-oxidized P700 species. The efficiencies of light-induced charge separation in the PSI film (10–35%) did not translate into an equally effective generation of photocurrent, whose internal quantum efficiency reached the maximal value of 0.47% at the lowest potentials. This mismatch indicates that the vast majority of the charge-separated states in multilayered PSI complexes underwent charge recombination.
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Affiliation(s)
- Sebastian Szewczyk
- Faculty of Physics, Adam Mickiewicz University in Poznań, ul. Uniwersytetu Poznańskiego 2, 61-614 Poznań, Poland; (S.S.); (A.G.); (G.B.)
| | - Alice Goyal
- Faculty of Physics, Adam Mickiewicz University in Poznań, ul. Uniwersytetu Poznańskiego 2, 61-614 Poznań, Poland; (S.S.); (A.G.); (G.B.)
| | - Mateusz Abram
- Solar Fuels Laboratory, Centre of New Technologies, University of Warsaw, Banacha 2C, 02-097 Warsaw, Poland;
- Faculty of Biology, University of Warsaw, Miecznikowa 1, 02-096 Warsaw, Poland
| | - Gotard Burdziński
- Faculty of Physics, Adam Mickiewicz University in Poznań, ul. Uniwersytetu Poznańskiego 2, 61-614 Poznań, Poland; (S.S.); (A.G.); (G.B.)
| | - Joanna Kargul
- Solar Fuels Laboratory, Centre of New Technologies, University of Warsaw, Banacha 2C, 02-097 Warsaw, Poland;
- Correspondence: (J.K.); (K.G.); Tel.: +48-22-5543760 (J.K.); +48-61-8296390 (K.G.)
| | - Krzysztof Gibasiewicz
- Faculty of Physics, Adam Mickiewicz University in Poznań, ul. Uniwersytetu Poznańskiego 2, 61-614 Poznań, Poland; (S.S.); (A.G.); (G.B.)
- Correspondence: (J.K.); (K.G.); Tel.: +48-22-5543760 (J.K.); +48-61-8296390 (K.G.)
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Kozuleva MA, Ivanov BN, Vetoshkina DV, Borisova-Mubarakshina MM. Minimizing an Electron Flow to Molecular Oxygen in Photosynthetic Electron Transfer Chain: An Evolutionary View. FRONTIERS IN PLANT SCIENCE 2020; 11:211. [PMID: 32231675 PMCID: PMC7082748 DOI: 10.3389/fpls.2020.00211] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 02/11/2020] [Indexed: 05/10/2023]
Abstract
Recruitment of H2O as the final donor of electrons for light-governed reactions in photosynthesis has been an utmost breakthrough, bursting the evolution of life and leading to the accumulation of O2 molecules in the atmosphere. O2 molecule has a great potential to accept electrons from the components of the photosynthetic electron transfer chain (PETC) (so-called the Mehler reaction). Here we overview the Mehler reaction mechanisms, specifying the changes in the structure of the PETC of oxygenic phototrophs that probably had occurred as the result of evolutionary pressure to minimize the electron flow to O2. These changes are warranted by the fact that the efficient electron flow to O2 would decrease the quantum yield of photosynthesis. Moreover, the reduction of O2 leads to the formation of reactive oxygen species (ROS), namely, the superoxide anion radical and hydrogen peroxide, which cause oxidative stress to plant cells if they are accumulated at a significant amount. From another side, hydrogen peroxide acts as a signaling molecule. We particularly zoom in into the role of photosystem I (PSI) and the plastoquinone (PQ) pool in the Mehler reaction.
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Binding of ferredoxin NADP + oxidoreductase (FNR) to plant photosystem I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2019; 1860:689-698. [PMID: 31336103 DOI: 10.1016/j.bbabio.2019.07.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 07/11/2019] [Accepted: 07/18/2019] [Indexed: 12/17/2022]
Abstract
The binding of FNR to PSI has been postulated long ago, however, a clear evidence is still missing. In this work, using isothermal titration calorimetry (ITC), we found that FNR binds to photosystem I with its light harvesting complex I (PSI-LHCI) from C. reinhardtii with a 1:1 stoichiometry, a Kd of ~0.8 μM and ∆H of -20.7 kcal/mol. Titrations at different temperatures were used to determine the heat capacity change, ∆CP, of the binding, through which the size of the interface area between the proteins was assessed as ~3000 Å2. In a different set of ITC experiments, introduction of various sucrose concentrations was used to estimate that ~95 water molecules are released to the solvent. These observations support the notion of a binding site shared by few of the photosystem I - light harvesting complex I (PSI-LHCI) subunits in addition to PsaE. Based on these results, a hypothetical model was built for the binding site of FNR at PSI, using known crystallographic structures of: cyanobacterial PSI in complex with ferredoxin (Fd), plant PSI-LHCI and Fd:FNR complex from cyanobacteria. FNR binding site location is proposed to be at the foot of the stromal ridge and above the inner LHCI belt. It is expected to form contacts with PsaE, PsaB, PsaF and at least one of the LHCI. In addition, a ~4.5-fold increased affinity between FNR and PSI-LHCI under crowded 1 M sucrose environment led us to conclude that in C. reinhardtii FNR also functions as a subunit of PSI-LHCI.
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The Significance of Calcium in Photosynthesis. Int J Mol Sci 2019; 20:ijms20061353. [PMID: 30889814 PMCID: PMC6471148 DOI: 10.3390/ijms20061353] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 02/23/2019] [Accepted: 03/01/2019] [Indexed: 01/12/2023] Open
Abstract
As a secondary messenger, calcium participates in various physiological and biochemical reactions in plants. Photosynthesis is the most extensive biosynthesis process on Earth. To date, researchers have found that some chloroplast proteins have Ca2+-binding sites, and the structure and function of some of these proteins have been discussed in detail. Although the roles of Ca2+ signal transduction related to photosynthesis have been discussed, the relationship between calcium and photosynthesis is seldom systematically summarized. In this review, we provide an overview of current knowledge of calcium’s role in photosynthesis.
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Su X, Ma J, Pan X, Zhao X, Chang W, Liu Z, Zhang X, Li M. Antenna arrangement and energy transfer pathways of a green algal photosystem-I-LHCI supercomplex. NATURE PLANTS 2019; 5:273-281. [PMID: 30850819 DOI: 10.1038/s41477-019-0380-5] [Citation(s) in RCA: 91] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Accepted: 02/04/2019] [Indexed: 05/05/2023]
Abstract
During oxygenic photosynthesis, photosystems I and II (PSI and PSII) are essential for light-driven electron transport. Excitation energy transfer in PSI occurs extremely quickly, making it an efficient energy converter. In the alga Chlamydomonas reinhardtii (Cr), multiple units of light-harvesting complex I (LHCI) bind to the PSI core and function as peripheral antennae, forming a PSI-LHCI supercomplex. CrPSI-LHCI shows significantly larger antennae compared with plant PSI-LHCI while maintaining highly efficient energy transfer from LHCI to PSI. Here, we report structures of CrPSI-LHCI, solved by cryo-electron microscopy, revealing that up to ten LHCIs are associated with the PSI core. The structures provide detailed information about antenna organization and pigment arrangement within the supercomplexes. Highly populated and closely associated chlorophylls in the antennae explain the high efficiency of light harvesting and excitation energy transfer in CrPSI-LHCI.
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Affiliation(s)
- Xiaodong Su
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Jun Ma
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Xiaowei Pan
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Xuelin Zhao
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Wenrui Chang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Zhenfeng Liu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Xinzheng Zhang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China.
- Center for Biological Imaging, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
| | - Mei Li
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
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Nama S, Madireddi SK, Yadav RM, Subramanyam R. Non-photochemical quenching-dependent acclimation and thylakoid organization of Chlamydomonas reinhardtii to high light stress. PHOTOSYNTHESIS RESEARCH 2019; 139:387-400. [PMID: 29982908 DOI: 10.1007/s11120-018-0551-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Accepted: 06/30/2018] [Indexed: 05/19/2023]
Abstract
Light is essential for all photosynthetic organisms while an excess of it can lead to damage mainly the photosystems of the thylakoid membrane. In this study, we have grown Chlamydomonas reinhardtii cells in different intensities of high light to understand the photosynthetic process with reference to thylakoid membrane organization during its acclimation process. We observed, the cells acclimatized to long-term response to high light intensities of 500 and 1000 µmol m-2 s-1 with faster growth and more biomass production when compared to cells at 50 µmol m-2 s-1 light intensity. The ratio of Chl a/b was marginally decreased from the mid-log phase of growth at the high light intensity. Increased level of zeaxanthin and LHCSR3 expression was also found which is known to play a key role in non-photochemical quenching (NPQ) mechanism for photoprotection. Changes in photosynthetic parameters were observed such as increased levels of NPQ, marginal change in electron transport rate, and many other changes which demonstrate that cells were acclimatized to high light which is an adaptive mechanism. Surprisingly, PSII core protein contents have marginally reduced when compared to peripherally arranged LHCII in high light-grown cells. Further, we also observed alterations in stromal subunits of PSI and low levels of PsaG, probably due to disruption of PSI assembly and also its association with LHCI. During the process of acclimation, changes in thylakoid organization occurred in high light intensities with reduction of PSII supercomplex formation. This change may be attributed to alteration of protein-pigment complexes which are in agreement with circular dichoism spectra of high light-acclimatized cells, where decrease in the magnitude of psi-type bands indicates changes in ordered arrays of PSII-LHCII supercomplexes. These results specify that acclimation to high light stress through NPQ mechanism by expression of LHCSR3 and also observed changes in thylakoid protein profile/supercomplex formation lead to low photochemical yield and more biomass production in high light condition.
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Affiliation(s)
- Srilatha Nama
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, Telangana, India
| | - Sai Kiran Madireddi
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, Telangana, India
| | - Ranay Mohan Yadav
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, Telangana, India
| | - Rajagopal Subramanyam
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, Telangana, India.
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11
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Buchert F, Hamon M, Gäbelein P, Scholz M, Hippler M, Wollman FA. The labile interactions of cyclic electron flow effector proteins. J Biol Chem 2018; 293:17559-17573. [PMID: 30228184 PMCID: PMC6231120 DOI: 10.1074/jbc.ra118.004475] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 09/05/2018] [Indexed: 12/16/2022] Open
Abstract
The supramolecular organization of membrane proteins (MPs) is sensitive to environmental changes in photosynthetic organisms. Isolation of MP supercomplexes from the green algae Chlamydomonas reinhardtii, which are believed to contribute to cyclic electron flow (CEF) between the cytochrome b6f complex (Cyt-b6f) and photosystem I (PSI), proved difficult. We were unable to isolate a supercomplex containing both Cyt-b6f and PSI because in our hands, most of Cyt-b6f did not comigrate in sucrose density gradients, even upon using chemical cross-linkers or amphipol substitution of detergents. Assisted by independent affinity purification and MS approaches, we utilized disintegrating MP assemblies and demonstrated that the algae-specific CEF effector proteins PETO and ANR1 are bona fide Cyt-b6f interactors, with ANR1 requiring the presence of an additional, presently unknown, protein. We narrowed down the Cyt-b6f interface, where PETO is loosely attached to cytochrome f and to a stromal region of subunit IV, which also contains phosphorylation sites for the STT7 kinase.
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Affiliation(s)
- Felix Buchert
- From the Institut de Biologie Physico-Chimique, UMR7141 CNRS-Sorbonne-Université, 13 Rue P et M Curie, 75005 Paris, France
- the Institute of Plant Biology and Biotechnology, University of Münster, Schlossplatz 8, 48143 Münster, Germany, and
| | - Marion Hamon
- the Institut de Biologie Physico-Chimique, UMR8226/FRC550 CNRS-Sorbonne-Université, 13 Rue P et M Curie, 75005 Paris, France
| | - Philipp Gäbelein
- the Institute of Plant Biology and Biotechnology, University of Münster, Schlossplatz 8, 48143 Münster, Germany, and
| | - Martin Scholz
- the Institute of Plant Biology and Biotechnology, University of Münster, Schlossplatz 8, 48143 Münster, Germany, and
| | - Michael Hippler
- the Institute of Plant Biology and Biotechnology, University of Münster, Schlossplatz 8, 48143 Münster, Germany, and
| | - Francis-André Wollman
- From the Institut de Biologie Physico-Chimique, UMR7141 CNRS-Sorbonne-Université, 13 Rue P et M Curie, 75005 Paris, France,
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12
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Marco P, Kozuleva M, Eilenberg H, Mazor Y, Gimeson P, Kanygin A, Redding K, Weiner I, Yacoby I. Binding of ferredoxin to algal photosystem I involves a single binding site and is composed of two thermodynamically distinct events. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2018; 1859:234-243. [DOI: 10.1016/j.bbabio.2018.01.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2017] [Revised: 01/07/2018] [Accepted: 01/08/2018] [Indexed: 10/18/2022]
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13
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Düner M, Lambertz J, Mügge C, Hemschemeier A. The soluble guanylate cyclase CYG12 is required for the acclimation to hypoxia and trophic regimes in Chlamydomonas reinhardtii. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2018; 93:311-337. [PMID: 29161457 DOI: 10.1111/tpj.13779] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2017] [Revised: 11/03/2017] [Accepted: 11/09/2017] [Indexed: 05/27/2023]
Abstract
Oxygenic phototrophs frequently encounter environmental conditions that result in intracellular energy crises. Growth of the unicellular green alga Chlamydomonas reinhardtii in hypoxia in the light depends on acclimatory responses of which the induction of photosynthetic cyclic electron flow is essential. The microalga cannot grow in the absence of molecular oxygen (O2 ) in the dark, although it possesses an elaborate fermentation metabolism. Not much is known about how the microalga senses and signals the lack of O2 or about its survival strategies during energy crises. Recently, nitric oxide (NO) has emerged to be required for the acclimation of C. reinhardtii to hypoxia. In this study, we show that the soluble guanylate cyclase (sGC) CYG12, a homologue of animal NO sensors, is also involved in this response. CYG12 is an active sGC, and post-transcriptional down-regulation of the CYG12 gene impairs hypoxic growth and gene expression in C. reinhardtii. However, it also results in a disturbed photosynthetic apparatus under standard growth conditions and the inability to grow heterotrophically. Transcriptome profiles indicate that the mis-expression of CYG12 results in a perturbation of responses that, in the wild-type, maintain the cellular energy budget. We suggest that CYG12 is required for the proper operation of the photosynthetic apparatus which, in turn, is essential for survival in hypoxia and darkness.
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Affiliation(s)
- Melis Düner
- Department of Plant Biochemistry, Workgroup Photobiotechnology, Faculty of Biology and Biotechnology, Ruhr-University of Bochum, Universitätsstr. 150, 44801, Bochum, Germany
| | - Jan Lambertz
- Department of Plant Biochemistry, Workgroup Photobiotechnology, Faculty of Biology and Biotechnology, Ruhr-University of Bochum, Universitätsstr. 150, 44801, Bochum, Germany
| | - Carolin Mügge
- Junior Research Group for Microbial Biotechnology, Faculty of Biology and Biotechnology, Ruhr-University of Bochum, Universitätsstr. 150, 44801, Bochum, Germany
| | - Anja Hemschemeier
- Department of Plant Biochemistry, Workgroup Photobiotechnology, Faculty of Biology and Biotechnology, Ruhr-University of Bochum, Universitätsstr. 150, 44801, Bochum, Germany
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14
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Sétif P, Mutoh R, Kurisu G. Dynamics and energetics of cyanobacterial photosystem I:ferredoxin complexes in different redox states. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2017; 1858:483-496. [DOI: 10.1016/j.bbabio.2017.04.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 03/24/2017] [Accepted: 04/12/2017] [Indexed: 10/19/2022]
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15
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Interaction between the photoprotective protein LHCSR3 and C 2 S 2 Photosystem II supercomplex in Chlamydomonas reinhardtii. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2017; 1858:379-385. [DOI: 10.1016/j.bbabio.2017.02.015] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 02/23/2017] [Accepted: 02/27/2017] [Indexed: 11/27/2022]
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16
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Atkinson JT, Campbell I, Bennett GN, Silberg JJ. Cellular Assays for Ferredoxins: A Strategy for Understanding Electron Flow through Protein Carriers That Link Metabolic Pathways. Biochemistry 2016; 55:7047-7064. [DOI: 10.1021/acs.biochem.6b00831] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Joshua T. Atkinson
- Systems,
Synthetic, and Physical Biology Graduate Program, Rice University, MS-180, 6100 Main Street, Houston, Texas 77005, United States
| | - Ian Campbell
- Biochemistry
and Cell Biology Graduate Program, Rice University, MS-140, 6100
Main Street, Houston, Texas 77005, United States
| | - George N. Bennett
- Department
of Biosciences, Rice University, MS-140, 6100 Main Street, Houston, Texas 77005, United States
- Department
of Chemical and Biomolecular Engineering, Rice University, MS-362,
6100 Main Street, Houston, Texas 77005, United States
| | - Jonathan J. Silberg
- Department
of Biosciences, Rice University, MS-140, 6100 Main Street, Houston, Texas 77005, United States
- Department
of Bioengineering, Rice University, MS-142, 6100 Main Street, Houston, Texas 77005, United States
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17
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Devadasu ER, Madireddi SK, Nama S, Subramanyam R. Iron deficiency cause changes in photochemistry, thylakoid organization, and accumulation of photosystem II proteins in Chlamydomonas reinhardtii. PHOTOSYNTHESIS RESEARCH 2016; 130:469-478. [PMID: 27325385 DOI: 10.1007/s11120-016-0284-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 06/13/2016] [Indexed: 05/11/2023]
Abstract
A trace element, iron (Fe) plays a pivotal role in photosynthesis process which in turn mediates the plant growth and productivity. Here, we have focused majorly on the photochemistry of photosystem (PS) II, abundance of proteins, and organization of supercomplexes of thylakoids from Fe-depleted cells in Chlamydomonas reinhardtii. Confocal pictures show that the cell's size has been reduced and formed rosette-shaped palmelloids; however, there is no cell death. Further, the PSII photochemistry was reduced remarkably. Further, the photosynthetic efficiency analyzer data revealed that both donor and acceptor side of PSII were equally damaged. Additionally, the room-temperature emission spectra showed the fluorescence emission maxima increased due to impaired energy transfer from PSII to PSI. Furthermore, the protein data reveal that most of the proteins of reaction center and light-harvesting antenna were reduced in Fe-depleted cells. Additionally, the supercomplexes of PSI and PSII were destabilized from thylakoids under Fe-deficient condition showing that Fe is an important element in photosynthesis mechanism.
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Affiliation(s)
- Elsin Raju Devadasu
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Sai Kiran Madireddi
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Srilatha Nama
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India
| | - Rajagopal Subramanyam
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India.
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18
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Natali A, Gruber JM, Dietzel L, Stuart MCA, van Grondelle R, Croce R. Light-harvesting Complexes (LHCs) Cluster Spontaneously in Membrane Environment Leading to Shortening of Their Excited State Lifetimes. J Biol Chem 2016; 291:16730-9. [PMID: 27252376 DOI: 10.1074/jbc.m116.730101] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Indexed: 11/06/2022] Open
Abstract
The light reactions of photosynthesis, which include light-harvesting and charge separation, take place in the amphiphilic environment of the thylakoid membrane. The light-harvesting complex II (LHCII) is the main responsible for light absorption in plants and green algae and is involved in photoprotective mechanisms that regulate the amount of excited states in the membrane. The dual function of LHCII has been extensively studied in detergent micelles, but recent results have indicated that the properties of this complex differ in a lipid environment. In this work we checked these suggestions by studying LHCII in liposomes. By combining bulk and single molecule measurements, we monitored the fluorescence characteristics of liposomes containing single complexes up to densely packed proteoliposomes. We show that the natural lipid environment per se does not alter the properties of LHCII, which for single complexes remain very similar to that in detergent. However, we show that LHCII has the strong tendency to cluster in the membrane and that protein interactions and the extent of crowding modulate the lifetimes of the excited state in the membrane. Finally, the presence of LHCII monomers at low concentrations of complexes per liposome is discussed.
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Affiliation(s)
- Alberto Natali
- From the Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, 1081 HV Amsterdam, The Netherlands
| | - J Michael Gruber
- From the Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, 1081 HV Amsterdam, The Netherlands
| | - Lars Dietzel
- Institute of Molecular Biosciences, Goethe-University Frankfurt/M, 60438 Frankfurt, Germany, and
| | - Marc C A Stuart
- Electron Microscopy, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Rienk van Grondelle
- From the Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, 1081 HV Amsterdam, The Netherlands
| | - Roberta Croce
- From the Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, 1081 HV Amsterdam, The Netherlands,
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19
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Tian L, Dinc E, Croce R. LHCII Populations in Different Quenching States Are Present in the Thylakoid Membranes in a Ratio that Depends on the Light Conditions. J Phys Chem Lett 2015; 6:2339-44. [PMID: 26266614 DOI: 10.1021/acs.jpclett.5b00944] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
LHCII is the major antenna complex of plants and algae, where it is involved in light harvesting and photoprotection. Its properties have been extensively studied in vitro, after isolation of the pigment-protein complex from the membranes, but are these properties representative for LHCII in the thylakoid membrane? In this work, we have studied LHCII in the cells of the green alga C. reinhardtii acclimated to different light conditions in the absence of the other components of the photosynthetic apparatus. We show that LHCII exists in the membranes in different fluorescence quenching states, all having a shorter excited-state lifetime than isolated LHCII in detergent. The ratio between these populations depends on the light conditions, indicating that the light is able to regulate the properties of the complexes in the membrane.
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Affiliation(s)
- Lijin Tian
- Department of Physics and Astronomy, Faculty of Sciences and LaserLaB Amsterdam, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Emine Dinc
- Department of Physics and Astronomy, Faculty of Sciences and LaserLaB Amsterdam, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Roberta Croce
- Department of Physics and Astronomy, Faculty of Sciences and LaserLaB Amsterdam, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
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20
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Natali A, Croce R. Characterization of the major light-harvesting complexes (LHCBM) of the green alga Chlamydomonas reinhardtii. PLoS One 2015; 10:e0119211. [PMID: 25723534 PMCID: PMC4344250 DOI: 10.1371/journal.pone.0119211] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Accepted: 01/17/2015] [Indexed: 11/21/2022] Open
Abstract
Nine genes (LHCBM1-9) encode the major light-harvesting system of Chlamydomonas reinhardtii. Transcriptomic and proteomic analyses have shown that those genes are all expressed albeit in different amounts and some of them only in certain conditions. However, little is known about the properties and specific functions of the individual gene products because they have never been isolated. Here we have purified several complexes from native membranes and/or we have reconstituted them in vitro with pigments extracted from C. reinhardtii. It is shown that LHCBM1 and -M2/7 represent more than half of the LHCBM population in the membrane. LHCBM2/7 forms homotrimers while LHCBM1 seems to be present in heterotrimers. Trimers containing only type I LHCBM (M3/4/6/8/9) were also observed. Despite their different roles, all complexes have very similar properties in terms of pigment content, organization, stability, absorption, fluorescence and excited-state lifetimes. Thus the involvement of LHCBM1 in non-photochemical quenching is suggested to be due to specific interactions with other components of the membrane and not to the inherent quenching properties of the complex. Similarly, the overexpression of LHCBM9 during sulfur deprivation can be explained by its low sulfur content as compared with the other LHCBMs. Considering the highly conserved biochemical and spectroscopic properties, the major difference between the complexes may be in their capacity to interact with other components of the thylakoid membrane.
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Affiliation(s)
- Alberto Natali
- Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Roberta Croce
- Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
- * E-mail:
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21
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Giera W, Szewczyk S, McConnell MD, Snellenburg J, Redding KE, van Grondelle R, Gibasiewicz K. Excitation dynamics in Photosystem I from Chlamydomonas reinhardtii. Comparative studies of isolated complexes and whole cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:1756-68. [PMID: 24973599 DOI: 10.1016/j.bbabio.2014.06.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 06/15/2014] [Accepted: 06/18/2014] [Indexed: 11/17/2022]
Abstract
Identical time-resolved fluorescence measurements with ~3.5-ps resolution were performed for three types of PSI preparations from the green alga, Chlamydomonas reinhardtii: isolated PSI cores, isolated PSI-LHCI complexes and PSI-LHCI complexes in whole living cells. Fluorescence decay in these types of PSI preparations has been previously investigated but never under the same experimental conditions. As a result we present consistent picture of excitation dynamics in algal PSI. Temporal evolution of fluorescence spectra can be generally described by three decay components with similar lifetimes in all samples (6-8ps, 25-30ps, 166-314ps). In the PSI cores, the fluorescence decay is dominated by the two fastest components (~90%), which can be assigned to excitation energy trapping in the reaction center by reversible primary charge separation. Excitation dynamics in the PSI-LHCI preparations is more complex because of the energy transfer between the LHCI antenna system and the core. The average trapping time of excitations created in the well coupled LHCI antenna system is about 12-15ps longer than excitations formed in the PSI core antenna. Excitation dynamics in PSI-LHCI complexes in whole living cells is very similar to that observed in isolated complexes. Our data support the view that chlorophylls responsible for the long-wavelength emission are located mostly in LHCI. We also compared in detail our results with the literature data obtained for plant PSI.
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Affiliation(s)
- Wojciech Giera
- Department of Physics, Adam Mickiewicz University, ul. Umultowska 85, 61-614 Poznań, Poland.
| | - Sebastian Szewczyk
- Department of Physics, Adam Mickiewicz University, ul. Umultowska 85, 61-614 Poznań, Poland
| | - Michael D McConnell
- Department of Chemistry and Biochemistry, Arizona State University, 1711 S. Rural Rd, Box 871604, Tempe, AZ 85287-1604, USA
| | - Joris Snellenburg
- Department of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Kevin E Redding
- Department of Chemistry and Biochemistry, Arizona State University, 1711 S. Rural Rd, Box 871604, Tempe, AZ 85287-1604, USA
| | - Rienk van Grondelle
- Department of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Krzysztof Gibasiewicz
- Department of Physics, Adam Mickiewicz University, ul. Umultowska 85, 61-614 Poznań, Poland
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22
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Drop B, Webber-Birungi M, Yadav SK, Filipowicz-Szymanska A, Fusetti F, Boekema EJ, Croce R. Light-harvesting complex II (LHCII) and its supramolecular organization in Chlamydomonas reinhardtii. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:63-72. [DOI: 10.1016/j.bbabio.2013.07.012] [Citation(s) in RCA: 115] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Revised: 07/23/2013] [Accepted: 07/30/2013] [Indexed: 11/25/2022]
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23
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Dinc E, Ramundo S, Croce R, Rochaix JD. Repressible chloroplast gene expression in Chlamydomonas: a new tool for the study of the photosynthetic apparatus. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1837:1548-52. [PMID: 24333785 DOI: 10.1016/j.bbabio.2013.11.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Revised: 11/26/2013] [Accepted: 11/29/2013] [Indexed: 11/18/2022]
Abstract
A repressible/inducible chloroplast gene expression system has been used to conditionally inhibit chloroplast protein synthesis in the unicellular alga Chlamydomonas reinhardtii. This system allows one to follow the fate of photosystem II and photosystem I and their antennae upon cessation of chloroplast translation. The main results are that the levels of the PSI core proteins decrease at a slower rate than those of PSII. Amongst the light-harvesting complexes, the decrease of CP26 proceeds at the same rate as for the PSII core proteins whereas it is significantly slower for CP29, and for the antenna complexes of PSI this rate is comprised between that of CP26 and CP29. In marked contrast, the components of trimeric LHCII, the major PSII antenna, persist for several days upon inhibition of chloroplast translation. This system offers new possibilities for investigating the biosynthesis and turnover of individual photosynthetic complexes in the thylakoid membranes. This article is part of a special issue entitled: photosynthesis research for sustainability: keys to produce clean energy.
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Affiliation(s)
- Emine Dinc
- Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, 1081 HV Amsterdam, The Netherlands
| | - Silvia Ramundo
- Departments of Molecular Biology and Plant Biology, University of Geneva, 30, Quai Ernest Ansermet, 1211 Geneva, Switzerland
| | - Roberta Croce
- Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, 1081 HV Amsterdam, The Netherlands
| | - Jean-David Rochaix
- Departments of Molecular Biology and Plant Biology, University of Geneva, 30, Quai Ernest Ansermet, 1211 Geneva, Switzerland.
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24
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Neelam S, Subramanyam R. Alteration of photochemistry and protein degradation of photosystem II from Chlamydomonas reinhardtii under high salt grown cells. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2013; 124:63-70. [DOI: 10.1016/j.jphotobiol.2013.04.007] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 04/13/2013] [Accepted: 04/17/2013] [Indexed: 01/05/2023]
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25
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Yadavalli V, Jolley CC, Malleda C, Thangaraj B, Fromme P, Subramanyam R. Alteration of proteins and pigments influence the function of photosystem I under iron deficiency from Chlamydomonas reinhardtii. PLoS One 2012; 7:e35084. [PMID: 22514709 PMCID: PMC3325961 DOI: 10.1371/journal.pone.0035084] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Accepted: 03/12/2012] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Iron is an essential micronutrient for all organisms because it is a component of enzyme cofactors that catalyze redox reactions in fundamental metabolic processes. Even though iron is abundant on earth, it is often present in the insoluble ferric [Fe (III)] state, leaving many surface environments Fe-limited. The haploid green alga Chlamydomonas reinhardtii is used as a model organism for studying eukaryotic photosynthesis. This study explores structural and functional changes in PSI-LHCI supercomplexes under Fe deficiency as the eukaryotic photosynthetic apparatus adapts to Fe deficiency. RESULTS 77K emission spectra and sucrose density gradient data show that PSI and LHCI subunits are affected under iron deficiency conditions. The visible circular dichroism (CD) spectra associated with strongly-coupled chlorophyll dimers increases in intensity. The change in CD signals of pigments originates from the modification of interactions between pigment molecules. Evidence from sucrose gradients and non-denaturing (green) gels indicates that PSI-LHCI levels were reduced after cells were grown for 72 h in Fe-deficient medium. Ultrafast fluorescence spectroscopy suggests that red-shifted pigments in the PSI-LHCI antenna were lost during Fe stress. Further, denaturing gel electrophoresis and immunoblot analysis reveals that levels of the PSI subunits PsaC and PsaD decreased, while PsaE was completely absent after Fe stress. The light harvesting complexes were also susceptible to iron deficiency, with Lhca1 and Lhca9 showing the most dramatic decreases. These changes in the number and composition of PSI-LHCI supercomplexes may be caused by reactive oxygen species, which increase under Fe deficiency conditions. CONCLUSIONS Fe deficiency induces rapid reduction of the levels of photosynthetic pigments due to a decrease in chlorophyll synthesis. Chlorophyll is important not only as a light-harvesting pigment, but also has a structural role, particularly in the pigment-rich LHCI subunits. The reduced level of chlorophyll molecules inhibits the formation of large PSI-LHCI supercomplexes, further decreasing the photosynthetic efficiency.
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Affiliation(s)
- Venkateswarlu Yadavalli
- Department of Biochemistry, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Craig C. Jolley
- Department of Chemistry and Biochemistry, Center for Bioenergy and Photosynthesis, Arizona State University, Tempe, Arizona, United States of America
| | - Chandramouli Malleda
- Department of Biochemistry, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Balakumar Thangaraj
- Department of Chemistry and Biochemistry, Center for Bioenergy and Photosynthesis, Arizona State University, Tempe, Arizona, United States of America
| | - Petra Fromme
- Department of Chemistry and Biochemistry, Center for Bioenergy and Photosynthesis, Arizona State University, Tempe, Arizona, United States of America
| | - Rajagopal Subramanyam
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India
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26
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Philipps G, Happe T, Hemschemeier A. Nitrogen deprivation results in photosynthetic hydrogen production in Chlamydomonas reinhardtii. PLANTA 2012; 235:729-45. [PMID: 22020754 DOI: 10.1007/s00425-011-1537-2] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Accepted: 10/06/2011] [Indexed: 05/10/2023]
Abstract
The unicellular green alga Chlamydomonas reinhardtii is able to use photosynthetically provided electrons for the production of molecular hydrogen by an [FeFe]-hydrogenase HYD1 accepting electrons from ferredoxin PetF. Despite the severe sensitivity of HYD1 towards oxygen, a sustained and relatively high photosynthetic hydrogen evolution capacity is established in C. reinhardtii cultures when deprived of sulfur. One of the major electron sources for proton reduction under this condition is the oxidation of starch and subsequent non-photochemical transfer of electrons to the plastoquinone pool. Here we report on the induction of photosynthetic hydrogen production by Chlamydomonas upon nitrogen starvation, a nutritional condition known to trigger the accumulation of large deposits of starch and lipids in the green alga. Photochemistry of photosystem II initially remained on a higher level in nitrogen-starved cells, resulting in a 2-day delay of the onset of hydrogen production compared with sulfur-deprived cells. Furthermore, though nitrogen-depleted cells accumulated large amounts of starch, both hydrogen yields and the extent of starch degradation were significantly lower than upon sulfur deficiency. Starch breakdown rates in nitrogen or sulfur-starved cultures transferred to darkness were comparable in both nutritional conditions. Methyl viologen treatment of illuminated cells significantly enhanced the efficiency of photosystem II photochemistry in sulfur-depleted cells, but had a minor effect on nitrogen-starved algae. Both the degradation of the cytochrome b₆ f complex which occurs in C. reinhardtii upon nitrogen starvation and lower ferredoxin amounts might create a bottleneck impeding the conversion of carbohydrate reserves into hydrogen evolution.
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Affiliation(s)
- Gabriele Philipps
- AG Photobiotechnologie, Fakultät für Biologie und Biotechnologie, Lehrstuhl für Biochemie der Pflanzen, Ruhr-Universität Bochum, 44780 Bochum, Germany
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27
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Drop B, Webber-Birungi M, Fusetti F, Kouřil R, Redding KE, Boekema EJ, Croce R. Photosystem I of Chlamydomonas reinhardtii contains nine light-harvesting complexes (Lhca) located on one side of the core. J Biol Chem 2011; 286:44878-87. [PMID: 22049081 PMCID: PMC3247965 DOI: 10.1074/jbc.m111.301101] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2011] [Revised: 10/28/2011] [Indexed: 11/06/2022] Open
Abstract
In this work we have purified the Photosystem I (PSI) complex of Chlamydomonas reinhardtii to homogeneity. Biochemical, proteomic, spectroscopic, and structural analyses reveal the main properties of this PSI-LHCI supercomplex. The data show that the largest purified complex is composed of one core complex and nine Lhca antennas and that it contains all Lhca gene products. A projection map at 15 Å resolution obtained by electron microscopy reveals that the Lhcas are organized on one side of the core in a double half-ring arrangement, in contrast with previous suggestions. A series of stable disassembled PSI-LHCI intermediates was purified. The analysis of these complexes suggests the sequence of the assembly/disassembly process. It is shown that PSI-LHCI of C. reinhardtii is larger but far less stable than the complex from higher plants. Lhca2 and Lhca9 (the red-most antenna complexes), although present in the largest complex in 1:1 ratio with the core, are only loosely associated with it. This can explain the large variation in antenna composition of PSI-LHCI from C. reinhardtii found in the literature. The analysis of several subcomplexes with reduced antenna size allows determination of the position of Lhca2 and Lhca9 and leads to a proposal for a model of the organization of the Lhcas within the PSI-LHCI supercomplex.
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Affiliation(s)
- Bartlomiej Drop
- From the Department of Biophysical Chemistry and
- the Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | | | - Fabrizia Fusetti
- Department of Biochemistry and the Netherlands Proteomics Centre, Groningen Biological Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Roman Kouřil
- From the Department of Biophysical Chemistry and
| | - Kevin E. Redding
- the Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, and
| | | | - Roberta Croce
- From the Department of Biophysical Chemistry and
- the Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
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Busch A, Hippler M. The structure and function of eukaryotic photosystem I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1807:864-77. [PMID: 20920463 DOI: 10.1016/j.bbabio.2010.09.009] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2010] [Revised: 09/20/2010] [Accepted: 09/28/2010] [Indexed: 12/27/2022]
Abstract
Eukaryotic photosystem I consists of two functional moieties: the photosystem I core, harboring the components for the light-driven charge separation and the subsequent electron transfer, and the peripheral light-harvesting complex (LHCI). While the photosystem I-core remained highly conserved throughout the evolution, with the exception of the oxidizing side of photosystem I, the LHCI complex shows a high degree of variability in size, subunits composition and bound pigments, which is due to the large variety of different habitats photosynthetic organisms dwell in. Besides summarizing the most current knowledge on the photosystem I-core structure, we will discuss the composition and structure of the LHCI complex from different eukaryotic organisms, both from the red and the green clade. Furthermore, mechanistic insights into electron transfer between the donor and acceptor side of photosystem I and its soluble electron transfer carrier proteins will be given. This article is part of a Special Issue entitled: Regulation of Electron Transport in Chloroplasts.
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Affiliation(s)
- Andreas Busch
- Department of Plant Biology and Biotechnology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
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29
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Subramanyam R, Jolley C, Thangaraj B, Nellaepalli S, Webber AN, Fromme P. Structural and functional changes of PSI-LHCI supercomplexes of Chlamydomonas reinhardtii cells grown under high salt conditions. PLANTA 2010; 231:913-922. [PMID: 20183922 DOI: 10.1007/s00425-009-1097-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The eVect of high salt concentration (100 mM NaCl) on the organization of photosystem I-light harvesting complex I supercomplexes (PSI-LHCI) of Chlamydomonas reinhardtii was studied. The electron transfer activity was reduced by 39% in isolated PSI-LHCI supercomplexes. The visible circular dichroism (CD) spectra associated with strongly coupled chlorophyll (Chl) dimers were reduced in intensity, indicating that pigment-pigment interactions were disrupted. This data is consistent with results from Xuorescence streak camera spectroscopy, which suggest that red-shifted pigments in the PSI-LHCI antenna had been lost. Denaturing gel electrophoresis and immunoblot analysis reveals that levels of the PSI reaction center proteins PsaD, PsaE and PsaF were reduced due to salt stress. PsaE is almost completely absent under high salt conditions. It is known that the membrane-extrinsic subunits PsaD and E form the ferredoxin-docking site. Our results indicate that the PSI-LHCI supercomplex is damaged by reactive oxygen species at high salt concentration, with particular impact on the ferredoxin-docking site and the PSILHCI interface.
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Affiliation(s)
- Rajagopal Subramanyam
- Department of Biochemistry, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India.
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30
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Jagannathan B, Golbeck JH. Understanding of the binding interface between PsaC and the PsaA/PsaB heterodimer in photosystem I. Biochemistry 2009; 48:5405-16. [PMID: 19432395 DOI: 10.1021/bi900243f] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The PsaC subunit of Photosystem I (PS I) is tightly bound to the PsaA/PsaB heterodimer via an extensive network of ionic and hydrogen bonds. To improve our understanding of the design of the PsaC-PsaA/PsaB binding interface, variants of PsaC were generated, each lacking a key binding contact with the PsaA/PsaB heterodimer. The characteristics of the reconstituted, variant PS I complexes were monitored by time-resolved optical spectroscopy, low-temperature EPR spectroscopy, and electron transfer throughput measurements. In the absence of the ionic bond forming contacts R52(C) or R65(C), a markedly slower charge recombination occurs between P(700)(+) and [F(A)/F(B)](-). The addition of PsaD leads to the restoration of native recombination kinetics in a fraction of the PS I complexes reconstituted with R52A(C), but not with R65A(C). Contrary to expectation, the absence of Y80(C), which forms two symmetry-breaking H-bonds with PsaB, does not significantly affect the binding of PsaC as judged by the rate of charge recombination between P(700)(+) and [F(A)/F(B)](-). However, the removal of the entire C-terminus results in a dramatic decrease in the rate of charge recombination. Low-temperature EPR spectra of the variant PS I complexes indicate that the magnetic environments of F(A) and F(B) are altered when compared to that of native PS I. The slowing of the rate of charge recombination in the variant PS I complexes could be due to an increase in the distance between F(X) and F(A)/F(B) as the result of non-native binding or to an altered reduction potential of the iron-sulfur clusters, which would result in a different rate of thermalization up the electron acceptor chain. The most significant finding is that the variant PS I complexes support lower rates of light-induced flavodoxin reduction and that the rates deteriorate rapidly on exposure to dioxygen due to the degradation of F(A) and F(B). We suggest that the extensive set of ionic bonds and H-bonds between PsaC and the PsaA/PsaB heterodimer has evolved to ensure an exceedingly tight binding interface, thereby rendering the [4Fe-4S] clusters in PsaC inaccessible to dioxygen at the onset of oxygenic photosynthesis.
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Affiliation(s)
- Bharat Jagannathan
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University,University Park, Pennsylvania 16802, USA
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31
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Grossman AR. In the Grip of Algal Genomics. TRANSGENIC MICROALGAE AS GREEN CELL FACTORIES 2008; 616:54-76. [DOI: 10.1007/978-0-387-75532-8_6] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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32
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Gulis G, Narasimhulu KV, Fox LN, Redding KE. Purification of His6-tagged Photosystem I from Chlamydomonas reinhardtii. PHOTOSYNTHESIS RESEARCH 2008; 96:51-60. [PMID: 18175204 DOI: 10.1007/s11120-007-9283-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2007] [Accepted: 12/10/2007] [Indexed: 05/25/2023]
Abstract
We have developed a rapid method for isolation of the Photosystem I (PS1) complex from Chlamydomonas reinhardtii using epitope tagging. Six histidine residues were genetically added to the N-terminus of the PsaA core subunit of PS1. The His(6)-tagged PS1 could be purified with a yield of 80-90% from detergent-solubilized thylakoid membranes within 3 h in a single step using a Ni-nitrilotriacetic acid (Ni-NTA) column. Immunoblots and low-temperature fluorescence analysis indicated that the His(6)-tagged PS1 preparation was highly pure and extremely low in uncoupled pigments. Moreover, the introduced tag appeared to have no adverse effect upon PS1 structure/function, as judged by photochemical assays and EPR spectroscopy of isolated particles, as well as photosynthetic growth tests of the tagged strain.
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Affiliation(s)
- Galina Gulis
- Department of Chemistry, University of Alabama, 206 Shelby Hall, 250 Hackberry Lane, Tuscaloosa, AL 35487-0336, USA
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33
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Abstract
Biolistic delivery of DNA initiated plastid transformation research and still is the most widelyused approach to generate transplastomic lines in both algae and higher plants. The principal designof transformation vectors is similar in both phylogenetic groups. Although important additions tothe list of species transformed in their plastomes have been made in algae and in higher plants, thekey organisms in the area are still the two species, in which stable plastid transformation was initiallysuccessful, i.e., Chlamydomonas reinhardtii and tobacco. Basicresearch into organelle biology has substantially benefited from the homologous recombination-basedcapability to precisely insert at predetermined loci, delete, disrupt, or exchange plastid genomesequences. Successful expression of recombinant proteins, including pharmaceutical proteins, hasbeen demonstrated in Chlamydomonas as well as in higher plants,where some interesting agronomic traits were also engineered through plastid transformation.
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34
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Lefebvre-Legendre L, Rappaport F, Finazzi G, Ceol M, Grivet C, Hopfgartner G, Rochaix JD. Loss of phylloquinone in Chlamydomonas affects plastoquinone pool size and photosystem II synthesis. J Biol Chem 2007; 282:13250-63. [PMID: 17339322 DOI: 10.1074/jbc.m610249200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phylloquinone functions as the electron transfer cofactor at the A(1) site of photosystem I. We have isolated and characterized a mutant of Chlamydomonas reinhardtii, menD1, that is deficient in MenD, which encodes 2-succinyl-6-hydroxy-2,4-cyclohexadiene-1-carboxylate synthase, an enzyme that catalyzes the first specific step of the phylloquinone biosynthetic pathway. The mutant is photosynthetically active but light-sensitive. Analysis of total pigments by mass spectrometry reveals that phylloquinone is absent in menD1, but plastoquinone levels are not affected. This is further confirmed by the rescue of menD1 by addition of phylloquinone to the growth medium. Analysis of electron transfer by absorption spectroscopy indicates that plastoquinone replaces phylloquinone in photosystem I and that electron transfer from A(1) to the iron-sulfur centers is slowed down at least 40-fold. Consistent with a replacement of phylloquinone by plastoquinone, the size of the free plastoquinone pool of menD1 is reduced by 20-30%. In contrast to cyanobacterial MenD-deficient mutants, photosystem I accumulates normally in menD1, whereas the level of photosystem II declines. This decrease is because of reduced synthesis of the photosystem II core subunits. The relationship between plastoquinone occupancy of the A(1) site in photosystem I and the reduced accumulation of photosystem II is discussed.
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Affiliation(s)
- Linnka Lefebvre-Legendre
- Department of Molecular Biology, University of Geneva, 30, Quai Ernest Ansermet 1211 Geneva 4, Switzerland
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35
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Ramadan T, Camargo SMR, Herzog B, Bordin M, Pos KM, Verrey F. Recycling of aromatic amino acids via TAT1 allows efflux of neutral amino acids via LAT2-4F2hc exchanger. Pflugers Arch 2007; 454:507-16. [PMID: 17273864 DOI: 10.1007/s00424-007-0209-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2006] [Accepted: 01/08/2007] [Indexed: 01/11/2023]
Abstract
The rate of amino acid efflux from individual cells needs to be adapted to cellular demands and plays a central role for the control of extracellular amino acid homeostasis. A particular example of such an outward amino acid transport is the basolateral efflux from transporting epithelial cells located in the small intestine and kidney proximal tubule. Because LAT2-4F2hc (Slc7a8-Slc3a2), the best known basolateral neutral amino acid transporter of these epithelial cells, functions as an obligatory exchanger, we tested whether TAT1 (Slc16a10), the aromatic amino-acid facilitated diffusion transporter, might allow amino acid efflux via this exchanger by recycling its influx substrates. In this study, we show by immunofluorescence that TAT1 and LAT2 indeed colocalize in the early kidney proximal tubule. Using the Xenopus laevis oocytes expression system, we show that L-glutamine is released from oocytes into an amino-acid-free medium only when both transporters are coexpressed. High-performance liquid chromatography analysis reveals that several other neutral amino acids are released as well. The transport function of both TAT1 and LAT2-4F2hc is necessary for this efflux, as coexpression of functionally inactive but surface-expressed mutants is ineffective. Based on negative results of coimmunoprecipitation and crosslinking experiments, the physical interaction of these transporters does not appear to be required. Furthermore, replacement of TAT1 or LAT2-4F2hc by the facilitated diffusion transporter LAT4 or the obligatory exchanger LAT1, respectively, supports similar functional cooperation. Taken together, the results suggest that the aromatic amino acid diffusion pathway TAT1 can control neutral amino acid efflux via neighboring exchanger LAT2-4F2hc, by recycling its aromatic influx substrates.
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MESH Headings
- Amino Acid Transport System y+/genetics
- Amino Acid Transport System y+/metabolism
- Amino Acid Transport Systems, Neutral/genetics
- Amino Acid Transport Systems, Neutral/metabolism
- Amino Acids, Aromatic/metabolism
- Amino Acids, Neutral/metabolism
- Animals
- Base Sequence
- Biological Transport, Active
- DNA Primers/genetics
- Female
- Fusion Regulatory Protein 1, Heavy Chain/genetics
- Fusion Regulatory Protein 1, Heavy Chain/metabolism
- Fusion Regulatory Protein 1, Light Chains
- In Vitro Techniques
- Kidney Tubules, Proximal/metabolism
- Mice
- Microscopy, Fluorescence
- Mutagenesis, Site-Directed
- Oocytes/metabolism
- Recombinant Proteins/genetics
- Recombinant Proteins/metabolism
- Xenopus laevis
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Affiliation(s)
- Tamara Ramadan
- Zurich Centre for Integrative Human Physiology, University of Zürich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
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36
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Ramesh VM, Gibasiewicz K, Lin S, Bingham SE, Webber AN. Replacement of the methionine axial ligand to the primary electron acceptor A0 slows the A0− reoxidation dynamics in Photosystem I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2007; 1767:151-60. [PMID: 17316554 DOI: 10.1016/j.bbabio.2006.12.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2006] [Revised: 11/28/2006] [Accepted: 12/22/2006] [Indexed: 12/01/2022]
Abstract
The recent crystal structure of photosystem I (PSI) from Thermosynechococcus elongatus shows two nearly symmetric branches of electron transfer cofactors including the primary electron donor, P(700), and a sequence of electron acceptors, A, A(0) and A(1), bound to the PsaA and PsaB heterodimer. The central magnesium atoms of each of the putative primary electron acceptor chlorophylls, A(0), are unusually coordinated by the sulfur atom of methionine 688 of PsaA and 668 of PsaB, respectively. We [Ramesh et al. (2004a) Biochemistry 43:1369-1375] have shown that the replacement of either methionine with histidine in the PSI of the unicellular green alga Chlamydomonas reinhardtii resulted in accumulation of A(0)(-) (in 300-ps time scale), suggesting that both the PsaA and PsaB branches are active. This is in contrast to cyanobacterial PSI where studies with methionine-to-leucine mutants show that electron transfer occurs predominantly along the PsaA branch. In this contribution we report that the change of methionine to either leucine or serine leads to a similar accumulation of A(0)(-) on both the PsaA and the PsaB branch of PSI from C. reinhardtii, as we reported earlier for histidine mutants. More importantly, we further demonstrate that for all the mutants under study, accumulation of A(0)(-) is transient, and that reoxidation of A(0)(-) occurs within 1-2 ns, two orders of magnitude slower than in wild type PSI, most likely via slow electron transfer to A(1). This illustrates an indispensable role of methionine as an axial ligand to the primary acceptor A(0) in optimizing the rate of charge stabilization in PSI. A simple energetic model for this reaction is proposed. Our findings support the model of equivalent electron transfer along both cofactor branches in Photosystem I.
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Affiliation(s)
- V M Ramesh
- School of Life Sciences, Arizona State University, Tempe, PO BOX 874501, AZ 85287-4501, USA
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37
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Li Y, van der Est A, Lucas MG, Ramesh VM, Gu F, Petrenko A, Lin S, Webber AN, Rappaport F, Redding K. Directing electron transfer within Photosystem I by breaking H-bonds in the cofactor branches. Proc Natl Acad Sci U S A 2006; 103:2144-9. [PMID: 16467143 PMCID: PMC1413687 DOI: 10.1073/pnas.0506537103] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Photosystem I has two branches of cofactors down which light-driven electron transfer (ET) could potentially proceed, each consisting of a pair of chlorophylls (Chls) and a phylloquinone (PhQ). Forward ET from PhQ to the next ET cofactor (FX) is described by two kinetic components with decay times of approximately 20 and approximately 200 ns, which have been proposed to represent ET from PhQB and PhQA, respectively. Immediately preceding each quinone is a Chl (ec3), which receives a H-bond from a nearby tyrosine. To decrease the reduction potential of each of these Chls, and thus modify the relative yield of ET within the targeted branch, this H-bond was removed by conversion of each Tyr to Phe in the green alga Chlamydomonas reinhardtii. Together, transient optical absorption spectroscopy performed in vivo and transient electron paramagnetic resonance data from thylakoid membranes showed that the mutations affect the relative amplitudes, but not the lifetimes, of the two kinetic components representing ET from PhQ to F(X). The mutation near ec3A increases the fraction of the faster component at the expense of the slower component, with the opposite effect seen in the ec3B mutant. We interpret this result as a decrease in the relative use of the targeted branch. This finding suggests that in Photosystem I, unlike type II reaction centers, the relative efficiency of the two branches is extremely sensitive to the energetics of the embedded redox cofactors.
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Affiliation(s)
- Yajing Li
- Department of Chemistry, University of Alabama, Tuscaloosa, AL 35487-0336
| | - Art van der Est
- Department of Chemistry, Brock University, 500 Glenridge Avenue, St. Catharines, ON, Canada L2S 3A1
| | - Marie Gabrielle Lucas
- Institut de Biologie Physico-Chimique, Unité Mixte de Recherche 714, Centre National de la Recherche∕Université Paris 6, 13 Rue Pierre et Marie Curie, 75005 Paris, France; and
| | - V. M. Ramesh
- Center for the Study of Early Events in Photosynthesis
- School of Life Science, and
| | - Feifei Gu
- Department of Chemistry, University of Alabama, Tuscaloosa, AL 35487-0336
| | - Alexander Petrenko
- Department of Chemistry, University of Alabama, Tuscaloosa, AL 35487-0336
| | - Su Lin
- Center for the Study of Early Events in Photosynthesis
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1601
| | - Andrew N. Webber
- Center for the Study of Early Events in Photosynthesis
- School of Life Science, and
| | - Fabrice Rappaport
- Institut de Biologie Physico-Chimique, Unité Mixte de Recherche 714, Centre National de la Recherche∕Université Paris 6, 13 Rue Pierre et Marie Curie, 75005 Paris, France; and
- To whom correspondence may be addressed. E-mail:
or
| | - Kevin Redding
- Department of Chemistry, University of Alabama, Tuscaloosa, AL 35487-0336
- To whom correspondence may be addressed. E-mail:
or
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38
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Subramanyam R, Jolley C, Brune DC, Fromme P, Webber AN. Characterization of a novel Photosystem I-LHCI supercomplex isolated fromChlamydomonas reinhardtiiunder anaerobic (State II) conditions. FEBS Lett 2005; 580:233-8. [PMID: 16375899 DOI: 10.1016/j.febslet.2005.12.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2005] [Revised: 11/25/2005] [Accepted: 12/01/2005] [Indexed: 10/25/2022]
Abstract
A novel supercomplex of Photosystem I (PSI) with light harvesting complex I (LHCI) was isolated from the green alga Chlamydomonas reinhardtii. This novel supercomplex is unique as it is the first stable supercomplex of PSI together with its external antenna. The supercomplex contains 256 chlorophylls per reaction center. The supercomplex was isolated under anaerobic conditions and may represent the State II form of the photosynthetic unit. In contrast to previously reported supercomplexes isolated in State I, which contain only 4 LHC I proteins, this supercomplex contains 10-11 LHC I proteins tightly bound to the PSI core. In contrast to plants, no LHC II is tightly bound to the PSI-LHCI supercomplex in State II. Investigation of the energy transfer from the antenna system to the reaction center core shows that the LHC supercomplexes are tightly coupled to the PSI core, not only structurally but also energetically. The excitation energy transfer kinetics are completely dominated by the fast phase, with a near-complete lack of long-lived fluorescence. This tight coupling is in contrast to all reports of energy transfer in PSI-LHCI supercomplexes (in State I), which have so far been described as weakly coupled supercomplexes with low efficiency for excitation energy transfer. These results indicate that there are large and dynamic changes of the PSI-LHCI supercomplex during the acclimation from aerobic (State I) to anaerobic (State II) conditions in Chlamydomonas.
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Affiliation(s)
- Rajagopal Subramanyam
- School of Life Sciences and Center for the Study of Early Events in Photosynthesis, P.O. Box, 874501, Arizona State University, Tempe, AZ 85287-4501, USA
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39
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Ishikita H, Stehlik D, Golbeck JH, Knapp EW. Electrostatic influence of PsaC protein binding to the PsaA/PsaB heterodimer in photosystem I. Biophys J 2005; 90:1081-9. [PMID: 16258043 PMCID: PMC1367094 DOI: 10.1529/biophysj.105.069781] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The absence of the PsaC subunit in the photosystem I (PSI) complex (native PSI complex) by mutagenesis or chemical manipulation yields a PSI core (P700-F(X) core) that also lacks subunits PsaD and PsaE and the two iron-sulfur clusters F(A) and F(B), which constitute an integral part of PsaC. In this P700-F(X) core, the redox potentials (E(m)) of the two quinones A(1A/B) and the iron-sulfur cluster F(X) as well as the corresponding protonation patterns are investigated by evaluating the electrostatic energies from the solution of the linearized Poisson-Boltzmann equation. The B-side specific Asp-B558 changes its protonation state significantly upon isolating the P700-F(X) core, being mainly protonated in the native PSI complex but ionized in the P700-F(X) core. In the P700-F(X) core, E(m)(A(1A/B)) remains practically unchanged, whereas E(m)(F(X)) is upshifted by 42 mV. With these calculated E(m) values, the electron transfer rate from A(1) to F(X) in the P700-F(X) core is estimated to be slightly faster on the A(1A) side than that of the wild type, which is consistent with kinetic measurements.
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Affiliation(s)
- Hiroshi Ishikita
- Institute of Chemistry and Biochemistry, Department of Biology, Free University of Berlin, D-14195 Berlin, Germany
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40
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Affiliation(s)
- Arthur R Grossman
- The Carnegie Institution, Department of Plant Biology, Stanford, California 94305, USA.
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41
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Li Y, Lucas MG, Konovalova T, Abbott B, MacMillan F, Petrenko A, Sivakumar V, Wang R, Hastings G, Gu F, van Tol J, Brunel LC, Timkovich R, Rappaport F, Redding K. Mutation of the putative hydrogen-bond donor to P700 of photosystem I. Biochemistry 2004; 43:12634-47. [PMID: 15449953 DOI: 10.1021/bi036329p] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The primary electron donor of photosystem I (PS1), called P(700), is a heterodimer of chlorophyll (Chl) a and a'. The crystal structure of photosystem I reveals that the chlorophyll a' (P(A)) could be hydrogen-bonded to the protein via a threonine residue, while the chlorophyll a (P(B)) does not have such a hydrogen bond. To investigate the influence of this hydrogen bond on P(700), PsaA-Thr739 was converted to alanine to remove the H-bond to the 13(1)-keto group of the chlorophyll a' in Chlamydomonas reinhardtii. The PsaA-T739A mutant was capable of assembling active PS1. Furthermore the mutant PS1 contained approximately one chlorophyll a' molecule per reaction center, indicating that P(700) was still a Chl a/a' heterodimer in the mutant. However, the mutation induced several band shifts in the visible P(700)(+) - P(700) absorbance difference spectrum. Redox titration of P(700) revealed a 60 mV decrease in the P(700)/P(700)(+) midpoint potential of the mutant, consistent with loss of a H-bond. Fourier transform infrared (FTIR) spectroscopy indicates that the ground state of P(700) is somewhat modified by mutation of ThrA739 to alanine. Comparison of FTIR difference band shifts upon P(700)(+) formation in WT and mutant PS1 suggests that the mutation modifies the charge distribution over the pigments in the P(700)(+) state, with approximately 14-18% of the positive charge on P(B) in WT being relocated onto P(A) in the mutant. (1)H-electron-nuclear double resonance (ENDOR) analysis of the P(700)(+) cation radical was also consistent with a slight redistribution of spin from the P(B) chlorophyll to P(A), as well as some redistribution of spin within the P(B) chlorophyll. High-field electron paramagnetic resonance (EPR) spectroscopy at 330-GHz was used to resolve the g-tensor of P(700)(+), but no significant differences from wild-type were observed, except for a slight decrease of anisotropy. The mutation did, however, provoke changes in the zero-field splitting parameters of the triplet state of P(700) ((3)P(700)), as determined by EPR. Interestingly, the mutation-induced change in asymmetry of P(700) did not cause an observable change in the directionality of electron transfer within PS1.
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Affiliation(s)
- Yajing Li
- Department Chemistry, University of Alabama, Tuscaloosa, Alabama 35487-0336, USA
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Grossman AR, Harris EE, Hauser C, Lefebvre PA, Martinez D, Rokhsar D, Shrager J, Silflow CD, Stern D, Vallon O, Zhang Z. Chlamydomonas reinhardtii at the crossroads of genomics. EUKARYOTIC CELL 2004; 2:1137-50. [PMID: 14665449 PMCID: PMC326643 DOI: 10.1128/ec.2.6.1137-1150.2003] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Arthur R Grossman
- The Carnegie Institution of Washington, Department of Plant Biology, Stanford, California 94305. Biology Department, Duke University, Durham, North Carolina 27708, USA.
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Golbeck JH. The binding of cofactors to photosystem I analyzed by spectroscopic and mutagenic methods. ANNUAL REVIEW OF BIOPHYSICS AND BIOMOLECULAR STRUCTURE 2003; 32:237-56. [PMID: 12524325 DOI: 10.1146/annurev.biophys.32.110601.142356] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This review focuses on cofactor-ligand and protein-protein interactions within the photosystem I reaction center. The topics include a description of the electron transfer cofactors, the mode of binding of the cofactors to protein-bound ligands, and a description of intraprotein contacts that ultimately allow photosystem I to be assembled (in cyanobacteria) from 96 chlorophylls, 22 carotenoids, 2 phylloquinones, 3 [4Fe-4S] clusters, and 12 polypeptides. During the 15 years that have elapsed from the first report of crystals to the atomic-resolution X-ray crystal structure, cofactor-ligand interactions and protein-protein interactions were systematically being explored by spectroscopic and genetic methods. This article charts the interplay between these disciplines and assesses how good the early insights were in light of the current structure of photosystem I.
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Affiliation(s)
- John H Golbeck
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
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Andersson U, Heddad M, Adamska I. Light stress-induced one-helix protein of the chlorophyll a/b-binding family associated with photosystem I. PLANT PHYSIOLOGY 2003; 132:811-20. [PMID: 12805611 PMCID: PMC167021 DOI: 10.1104/pp.102.019281] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2002] [Revised: 01/20/2003] [Accepted: 02/21/2003] [Indexed: 05/19/2023]
Abstract
The superfamily of light-harvesting chlorophyll a/b-binding (Lhc) proteins in higher plants and green algae is composed of more than 20 different antenna proteins associated either with photosystem I (PSI) or photosystem II (PSII). Several distant relatives of this family with conserved chlorophyll-binding residues and proposed photoprotective functions are induced transiently under various stress conditions. Whereas "classical" Lhc proteins contain three-transmembrane alpha-helices, their distant relatives span the membrane with between one and four transmembrane segments. Here, we report the identification and isolation of a novel member of the Lhc family from Arabidopsis with one predicted transmembrane alpha-helix closely related to helix I of Lhc protein from PSI (Lhca4) that we named Ohp2 (for a second one-helix protein of Lhc family described from higher plants). We showed that the Ohp2 gene expression is triggered by light stress and that the Ohp2 transcript and protein accumulated in a light intensity-dependent manner. Other stress conditions did not up-regulate the expression of the Ohp2 gene. Localization studies revealed that Ohp2 is associated with PSI under low- or high-light conditions. Because all stress-induced Lhc relatives reported so far were found in PSII, we propose that the accumulation of Ohp2 might represent a novel photoprotective strategy induced within PSI in response to light stress.
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Affiliation(s)
- Ulrica Andersson
- Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, Sweden
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Kargul J, Nield J, Barber J. Three-dimensional reconstruction of a light-harvesting complex I-photosystem I (LHCI-PSI) supercomplex from the green alga Chlamydomonas reinhardtii. Insights into light harvesting for PSI. J Biol Chem 2003; 278:16135-41. [PMID: 12588873 DOI: 10.1074/jbc.m300262200] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A supercomplex containing the photosystem I (PSI) and chlorophyll a/b light-harvesting complex I (LHCI) has been isolated using a His-tagged mutant of Chlamydomonas reinhardtii. This LHCI-PSI supercomplex contained approximately 215 chlorophyll molecules of which 175 were estimated to be chlorophyll a and 40 to be chlorophyll b, based on P700 oxidation and chlorophyll a/b ratio measurements. Its room temperature long wavelength absorption peak was at 680 nm, and it emitted chlorophyll fluorescence maximally at 715 nm (77 K). The LHCI was composed of four or more different types of Lhca polypeptides including Lhca3. No LHCII proteins or other phosphoproteins were detected in the LHCI-PSI supercomplexes suggesting that the cells from which they were isolated were in State 1. Electron microscopy of negatively stained samples followed by image analysis revealed the LHCI-PSI supercomplex to have maximal dimensions of 220 A by 180 A and to be approximately 105 A thick. An averaged top view was used to model in x-ray and electron crystallographic data for PSI and Lhca proteins respectively. We conclude that the supercomplex consists of a PSI reaction center monomer with 11 Lhca proteins arranged along the side where the PSI proteins, PsaK, PsaJ, PsaF, and PsaG are located. The estimated molecular mass for the complex is 700 kDa including the bound chlorophyll molecules. The assignment of 11 Lhca proteins is consistent with a total chlorophyll level of 215 assuming that the PSI reaction center core binds approximately 100 chlorophylls and that each Lhca subunit binds 10 chlorophylls. There was no evidence for oligomerization of Chlamydomonas PSI in contrast to the trimerization of PSI in cyanobacteria.
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Affiliation(s)
- Joanna Kargul
- Wolfson Laboratories, Department of Biological Sciences, South Kensington Campus, Imperial College London, London SW7 2AZ, United Kingdom
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Franklin JL, Zhang J, Redding K. Use of aminoglycoside adenyltransferase translational fusions to determine topology of thylakoid membrane proteins. FEBS Lett 2003; 536:97-100. [PMID: 12586345 DOI: 10.1016/s0014-5793(03)00034-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
We have developed a system to examine the topology of thylakoid membrane proteins using the bacterial aadA gene as a reporter. Translational fusions that place the aminoglycoside adenyltransferase domain in the stroma should provide high antibiotic resistance, while those that place it in the thylakoid lumen should give rise to low resistance. Genes encoding chimeric polypeptides consisting of AadA fused to varying lengths of the PsaA polypeptide, whose topology is known, were introduced into the chloroplast genome of Chlamydomonas reinhardtii. As expected, chimeras with an even number of alpha-helices in general resulted in higher resistance. This effect was not due to differences in expression or in catalytic activity. This system should prove useful in analysis of novel proteins predicted to be localized to the thylakoid membrane.
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Affiliation(s)
- John Lee Franklin
- Department of Chemistry, The University of Alabama, 120 Lloyd Hall, 6th Ave., Tuscaloosa, AL 35487-0336, USA.
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Sétif P, Fischer N, Lagoutte B, Bottin H, Rochaix JD. The ferredoxin docking site of photosystem I. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1555:204-9. [PMID: 12206916 DOI: 10.1016/s0005-2728(02)00279-7] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reaction center of photosystem I (PSI) reduces soluble ferredoxin on the stromal side of the photosynthetic membranes of cyanobacteria and chloroplasts. The X-ray structure of PSI from the cyanobacterium Synechococcus elongatus has been recently established at a 2.5 A resolution [Nature 411 (2001) 909]. The kinetics of ferredoxin photoreduction has been studied in recent years in many mutants of the stromal subunits PsaC, PsaD and PsaE of PSI. We discuss the ferredoxin docking site of PSI using the X-ray structure and the effects brought by the PSI mutations to the ferredoxin affinity.
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Affiliation(s)
- Pierre Sétif
- CEA Saclay, Département de Biologie Joliot-Curie, Service de Bioénergétique and URA CNRS 2096, 91191 Gif sur Yvette, Cedex, France.
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Witt H, Schlodder E, Teutloff C, Niklas J, Bordignon E, Carbonera D, Kohler S, Labahn A, Lubitz W. Hydrogen bonding to P700: site-directed mutagenesis of threonine A739 of photosystem I in Chlamydomonas reinhardtii. Biochemistry 2002; 41:8557-69. [PMID: 12093272 DOI: 10.1021/bi025822i] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The primary electron donor P700 of photosystem I is a dimer comprised of chlorophyll a (P(B)) and chlorophyll a' (P(A)). P(A) is involved in a hydrogen bond network with several surrounding amino acid residues and a nearby water molecule. To investigate the influence of hydrogen bond interactions on the properties of P700, the threonine at position A739, which donates a putative hydrogen bond to the 13(1)-keto group of P(A), was replaced with valine, histidine, and tyrosine in Chlamydomonas reinhardtii using site-directed mutagenesis. Growth of the mutants was not impaired. (i) The (P700(+)* - P700) FTIR difference spectra of the mutants lack a negative band at 1634 cm(-1) observed in the wild-type spectrum and instead exhibit a new negative band between 1658 and 1672 cm(-1) depending on the mutation. This band can therefore be assigned to the 13(1)-keto group of P(A) which is upshifted to higher frequencies upon removal of the hydrogen bond. (ii) The main bleaching band in the Q(y)() region of the (P700(+)* - P700) and ((3)P700 - P700) absorption difference spectra is blue shifted for the mutants by approximately 6 nm compared to that of the wild type. A blue shift is also observed for the main bleaching in the Soret region. (iii) The (P700(+)* - P700) CD difference spectrum of the wild type reveals two bands at 694 nm (positive CD) and 680 nm (negative CD) of approximately equal area. For each mutant, these two components are blue-shifted to the same extent. The results strongly suggest that a blue shift of the Q(y) absorption band of P(A) is responsible for a blue shift of the exciton bands. (iv) Redox titrations yielded a decrease in the midpoint potential for the oxidation of P700 by 32 mV for the exchange of Thr against Val. (v) ENDOR spectroscopy shows that the hfc of the methyl protons at position 12 of the spin-carrying Chl P(B) is decreased due to the removal of the hydrogen bond to P(A). This indicates a redistribution of spin density in P700(+)* compared to that in the wild type. This gives evidence for an electronic coupling between the two halves of the dimer in the wild type and mutants.
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Affiliation(s)
- Heike Witt
- Max-Volmer-Laboratorium für Biophysikalische Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany.
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Hauska G, Schoedl T, Remigy H, Tsiotis G. The reaction center of green sulfur bacteria(1). BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1507:260-77. [PMID: 11687219 DOI: 10.1016/s0005-2728(01)00200-6] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The composition of the P840-reaction center complex (RC), energy and electron transfer within the RC, as well as its topographical organization and interaction with other components in the membrane of green sulfur bacteria are presented, and compared to the FeS-type reaction centers of Photosystem I and of Heliobacteria. The core of the RC is homodimeric, since pscA is the only gene found in the genome of Chlorobium tepidum which resembles the genes psaA and -B for the heterodimeric core of Photosystem I. Functionally intact RC can be isolated from several species of green sulfur bacteria. It is generally composed of five subunits, PscA-D plus the BChl a-protein FMO. Functional cores, with PscA and PscB only, can be isolated from Prostecochloris aestuarii. The PscA-dimer binds P840, a special pair of BChl a-molecules, the primary electron acceptor A(0), which is a Chl a-derivative and FeS-center F(X). An equivalent to the electron acceptor A(1) in Photosystem I, which is tightly bound phylloquinone acting between A(0) and F(X), is not required for forward electron transfer in the RC of green sulfur bacteria. This difference is reflected by different rates of electron transfer between A(0) and F(X) in the two systems. The subunit PscB contains the two FeS-centers F(A) and F(B). STEM particle analysis suggests that the core of the RC with PscA and PscB resembles the PsaAB/PsaC-core of the P700-reaction center in Photosystem I. PscB may form a protrusion into the cytoplasmic space where reduction of ferredoxin occurs, with FMO trimers bound on both sides of this protrusion. Thus the subunit composition of the RC in vivo should be 2(FMO)(3)(PscA)(2)PscB(PscC)(2)PscD. Only 16 BChl a-, four Chl a-molecules and two carotenoids are bound to the RC-core, which is substantially less than its counterpart of Photosystem I, with 85 Chl a-molecules and 22 carotenoids. A total of 58 BChl a/RC are present in the membranes of green sulfur bacteria outside the chlorosomes, corresponding to two trimers of FMO (42 Bchl a) per RC (16 BChl a). The question whether the homodimeric RC is totally symmetric is still open. Furthermore, it is still unclear which cytochrome c is the physiological electron donor to P840(+). Also the way of NAD(+)-reduction is unknown, since a gene equivalent to ferredoxin-NADP(+) reductase is not present in the genome.
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Affiliation(s)
- G Hauska
- Lehstuhl für Zellbiologie und Pflanzenphysiologie, Universität Regensburg, Germany.
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