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Transcriptional Analysis of Microcystis aeruginosa Co-Cultured with Algicidal Bacteria Brevibacillus laterosporus. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:ijerph18168615. [PMID: 34444364 PMCID: PMC8394347 DOI: 10.3390/ijerph18168615] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 08/09/2021] [Accepted: 08/12/2021] [Indexed: 11/17/2022]
Abstract
Harmful algal blooms caused huge ecological damage and economic losses around the world. Controlling algal blooms by algicidal bacteria is expected to be an effective biological control method. The current study investigated the molecular mechanism of harmful cyanobacteria disrupted by algicidal bacteria. Microcystis aeruginosa was co-cultured with Brevibacillus laterosporus Bl-zj, and RNA-seq based transcriptomic analysis was performed compared to M. aeruginosa, which was cultivated separately. A total of 1706 differentially expressed genes were identified, which were mainly involved in carbohydrate metabolism, energy metabolism and amino acid metabolism. In the co-cultured group, the expression of genes mainly enriched in photosynthesis and oxidative phosphorylation were significantly inhibited. However, the expression of the genes related to fatty acid synthesis increased. In addition, the expression of the antioxidant enzymes, such as 2-Cys peroxiredoxin, was increased. These results suggested that B. laterosporus could block the electron transport by attacking the PSI system and complex I of M. aeruginosa, affecting the energy acquisition and causing oxidative damage. This further led to the lipid peroxidation of the microalgal cell membrane, resulting in algal death. The transcriptional analysis of algicidal bacteria in the interaction process can be combined to explain the algicidal mechanism in the future.
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Sagun JV, Badger MR, Chow WS, Ghannoum O. Mehler reaction plays a role in C 3 and C 4 photosynthesis under shade and low CO 2. PHOTOSYNTHESIS RESEARCH 2021; 149:171-185. [PMID: 33534052 DOI: 10.1007/s11120-021-00819-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 01/09/2021] [Indexed: 06/12/2023]
Abstract
Alternative electron fluxes such as the cyclic electron flux (CEF) around photosystem I (PSI) and Mehler reaction (Me) are essential for efficient photosynthesis because they generate additional ATP and protect both photosystems against photoinhibition. The capacity for Me can be estimated by measuring O2 exchange rate under varying irradiance and CO2 concentration. In this study, mass spectrometric measurements of O2 exchange were made using leaves of representative species of C3 and C4 grasses grown under natural light (control; PAR ~ 800 µmol quanta m-2 s-1) and shade (~ 300 µmol quanta m-2 s-1), and in representative species of gymnosperm, liverwort and fern grown under natural light. For all control grown plants measured at high CO2, O2 uptake rates were similar between the light and dark, and the ratio of Rubisco oxygenation to carboxylation (Vo/Vc) was low, which suggests little potential for Me, and that O2 uptake was mainly due to photorespiration or mitochondrial respiration under these conditions. Low CO2 stimulated O2 uptake in the light, Vo/Vc and Me in all species. The C3 species had similar Vo/Vc, but Me was highest in the grass and lowest in the fern. Among the C4 grasses, shade increased O2 uptake in the light, Vo/Vc and the assimilation quotient (AQ), particularly at low CO2, whilst Me was only substantial at low CO2 where it may contribute 20-50% of maximum electron flow under high light.
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Affiliation(s)
- Julius Ver Sagun
- ARC Centre of Excellence for Translational Photosynthesis, Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, Locked Bag 1797, Penrith, NSW, 2751, Australia
| | - Murray R Badger
- ARC Centre of Excellence for Translational Photosynthesis, Research School of Biology, Australian National University, Canberra, ACT, 2601, Australia
| | - Wah Soon Chow
- ARC Centre of Excellence for Translational Photosynthesis, Research School of Biology, Australian National University, Canberra, ACT, 2601, Australia
| | - Oula Ghannoum
- ARC Centre of Excellence for Translational Photosynthesis, Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, Locked Bag 1797, Penrith, NSW, 2751, Australia.
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Mohanta TK, Khan A, Hashem A, Abd Allah EF, Al-Harrasi A. The molecular mass and isoelectric point of plant proteomes. BMC Genomics 2019; 20:631. [PMID: 31382875 PMCID: PMC6681478 DOI: 10.1186/s12864-019-5983-8] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Accepted: 07/17/2019] [Indexed: 01/02/2023] Open
Abstract
Background Cell contain diverse array of proteins with different molecular weight and isoelectric point (pI). The molecular weight and pI of protein play important role in determining the molecular biochemical function. Therefore, it was important to understand the detail regarding the molecular weight and pI of the plant proteins. Results A proteome-wide analysis of plant proteomes from 145 species revealed a pI range of 1.99 (epsin) to 13.96 (hypothetical protein). The spectrum of molecular mass of the plant proteins varied from 0.54 to 2236.8 kDa. A putative Type-I polyketide synthase (22244 amino acids) in Volvox carteri was found to be the largest protein in the plant kingdom. However, Type-I polyketide synthase was not found in higher plant species. Titin (806.46 kDa) and misin/midasin (730.02 kDa) were the largest proteins identified in higher plant species. The pI and molecular weight of the plant proteins showed a trimodal distribution. An acidic pI (56.44% of proteins) was found to be predominant over a basic pI (43.34% of proteins) and the abundance of acidic pI proteins was higher in unicellular algae species relative to multicellular higher plants. In contrast, the seaweed, Porphyra umbilicalis, possesses a higher proportion of basic pI proteins (70.09%). Plant proteomes were also found to contain selenocysteine (Sec), amino acid that was found only in lower eukaryotic aquatic plant lineage. Amino acid composition analysis showed Leu was high and Trp was low abundant amino acids in the plant proteome. Additionally, the plant proteomes also possess ambiguous amino acids Xaa (unknown), Asx (asparagine or aspartic acid), Glx (glutamine or glutamic acid), and Xle (leucine or isoleucine) as well. Conclusion The diverse molecular weight and isoelectric point range of plant proteome will be helpful to understand their biochemical and functional aspects. The presence of selenocysteine proteins in lower eukaryotic organism is of interest and their expression in higher plant system can help us to understand their functional role. Electronic supplementary material The online version of this article (10.1186/s12864-019-5983-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Tapan Kumar Mohanta
- Natural and Medical Science Research Centre, University of Nizwa, 616, Nizwa, Oman.
| | - Abdullatif Khan
- Natural and Medical Science Research Centre, University of Nizwa, 616, Nizwa, Oman
| | - Abeer Hashem
- Botany and Microbiology Department, King Saud University, Riyadh, 11451, Saudi Arabia
| | | | - Ahmed Al-Harrasi
- Natural and Medical Science Research Centre, University of Nizwa, 616, Nizwa, Oman.
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Ness J, Naurin S, Effinger K, Stadnytskyi V, Ibrahim IM, Puthiyaveetil S, Cramer WA. Structure‐based control of the rate limitation of photosynthetic electron transport. FEBS Lett 2019; 593:2103-2111. [PMID: 31198994 DOI: 10.1002/1873-3468.13484] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Accepted: 06/04/2019] [Indexed: 12/11/2022]
Affiliation(s)
- Jillian Ness
- Department of Biological Sciences Purdue University West Lafayette IN USA
| | - Sejuti Naurin
- Department of Biological Sciences Purdue University West Lafayette IN USA
| | | | | | | | | | - William A. Cramer
- Department of Biological Sciences Purdue University West Lafayette IN USA
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Gao J, Wang H, Yuan Q, Feng Y. Structure and Function of the Photosystem Supercomplexes. FRONTIERS IN PLANT SCIENCE 2018; 9:357. [PMID: 29616068 PMCID: PMC5869908 DOI: 10.3389/fpls.2018.00357] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 03/02/2018] [Indexed: 05/21/2023]
Abstract
Photosynthesis converts solar energy into chemical energy to sustain all life on earth by providing oxygen and food, and controlling the atmospheric carbon dioxide. During this process, the water-splitting and oxygen-evolving reaction is catalyzed by photosystem II (PSII), while photosystem I (PSI) generates the reducing power for the reduction of NADP+ to NADPH. Together with their peripheral light-harvesting complexes (LHCs), photosystems function as multisubunit supercomplexes located in the thylakoid membranes of cyanobacteria, algae, and plants. Recent advances in single-particle cryo-electron microscopy (cryoEM), X-ray free electron laser (XFEL) and other techniques have revealed unprecedented structural and catalytic details concerning the two supercomplexes. Several high-resolution structures of the complexes from plants were solved, and serial time-resolved crystallography and "radiation-damage-free" femtosecond XFEL also provided important insights into the mechanism of water oxidation. Here, we review these exciting advances in the studies of the photosystem supercomplexes with an emphasis on PSII-LHCII, propose presently unresolved problems in this field, and suggest potential tendencies for future studies.
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Affiliation(s)
- Jinlan Gao
- State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Hao Wang
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, China
| | - Qipeng Yuan
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, China
| | - Yue Feng
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, China
- *Correspondence: Yue Feng, ;
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Króliczewski J, Bartoszewski R, Króliczewska B. Chloroplast PetD protein: evidence for SRP/Alb3-dependent insertion into the thylakoid membrane. BMC PLANT BIOLOGY 2017; 17:213. [PMID: 29162052 PMCID: PMC5697057 DOI: 10.1186/s12870-017-1176-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Accepted: 11/13/2017] [Indexed: 05/24/2023]
Abstract
BACKGROUND In thylakoid membrane, each monomer of the dimeric complex of cytochrome b 6 f is comprised of eight subunits that are both nucleus- and plastid-encoded. Proper cytochrome b 6 f complex integration into the thylakoid membrane requires numerous regulatory factors for coordinated transport, insertion and assembly of the subunits. Although, the chloroplast-encoded cytochrome b 6 f subunit IV (PetD) consists of three transmembrane helices, the signal and the mechanism of protein integration into the thylakoid membrane have not been identified. RESULTS Here, we demonstrate that the native PetD subunit cannot incorporate into the thylakoid membranes spontaneously, but that proper integration occurs through the post-translational signal recognition particle (SRP) pathway. Furthermore, we show that PetD insertion into thylakoid membrane involves the coordinated action of cpFTSY, cpSRP54 and ALB3 insertase. CONCLUSIONS PetD subunit integration into the thylakoid membrane is a post-translational and an SRP-dependent process that requires the formation of the cpSRP-cpFtsY-ALB3-PetD complex. This data provides a new insight into the molecular mechanisms by which membrane proteins integration into the thylakoid membrane is accomplished and is not limited to PetD.
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Affiliation(s)
- Jarosław Króliczewski
- Faculty of Biotechnology, University of Wrocław, Fryderyka Joliot-Curie 14a, 50-383 Wrocław, Poland
| | - Rafał Bartoszewski
- Department of Biology and Pharmaceutical Botany Medical University of Gdańsk, Hallera 107, 80-416 Gdansk, Poland
| | - Bożena Króliczewska
- Department of Animal Physiology and Biostructure, Faculty of Veterinary Medicine Wroclaw University of Environmental and Life Sciences, C.K Norwida 31, 50-375 Wrocław, Poland
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Jian J, Zeng D, Wei W, Lin H, Li P, Liu W. The Combination of RNA and Protein Profiling Reveals the Response to Nitrogen Depletion in Thalassiosira pseudonana. Sci Rep 2017; 7:8989. [PMID: 28827639 PMCID: PMC5566445 DOI: 10.1038/s41598-017-09546-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Accepted: 07/24/2017] [Indexed: 12/21/2022] Open
Abstract
Nitrogen (N) is essential for the growth of algae, and its concentration varies greatly in the ocean, which has been regarded as a limitation for phytoplankton growth. Despite its great importance, most of the existing studies on the mechanisms underlying the effects of N on diatoms have focused on physiology, biochemistry and a few target genes and have rarely involved whole genomic analyses. Therefore, in this study, we integrated physiological data with RNA and protein profiling data to reveal the response strategy of Thalassiosira pseudonana under N-depleted conditions. Physiological measurements indicated that the cell growth capacity and chlorophyll content of the cells decreased, as did the expression of photosynthesis- and chlorophyll biosynthesis-related genes or proteins. The RNA-Seq profile results showed that T. pseudonana responded to N deprivation through increases in glycolysis, the TCA cycle and N metabolism as well as down-regulation in the Calvin cycle, gluconeogenesis, pentose phosphate, oxidative phosphorylation and lipid synthesis. These results provide a basic understanding for further research addressing how N affects phytoplankton in terms of genomics.
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Affiliation(s)
- Jianbo Jian
- Marine Biology Institute, Shantou University, Shantou, Guangdong, 515063, P.R. China
| | - Dezhi Zeng
- Marine Biology Institute, Shantou University, Shantou, Guangdong, 515063, P.R. China
| | - Wei Wei
- Marine Biology Institute, Shantou University, Shantou, Guangdong, 515063, P.R. China
| | - Hongmin Lin
- Marine Biology Institute, Shantou University, Shantou, Guangdong, 515063, P.R. China
| | - Ping Li
- Marine Biology Institute, Shantou University, Shantou, Guangdong, 515063, P.R. China.
| | - Wenhua Liu
- Marine Biology Institute, Shantou University, Shantou, Guangdong, 515063, P.R. China.
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Chauvet AAP, Agarwal R, Haddad AA, van Mourik F, Cramer WA. Photo-induced oxidation of the uniquely liganded heme f in the cytochrome b6f complex of oxygenic photosynthesis. Phys Chem Chem Phys 2016; 18:12983-91. [PMID: 27108913 PMCID: PMC4990003 DOI: 10.1039/c6cp01592a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The ultrafast behavior of the ferrous heme f from the cytochrome b6f complex of oxygenic photosynthesis is revealed by means of transient absorption spectroscopy. Benefiting from the use of microfluidic technologies for handling the sample as well as from a complementary frame-by-frame analysis of the heme dynamics, the different relaxation mechanisms from vibrationally excited states are disentangled and monitored via the shifts of the heme α-absorption band. Under 520 nm laser excitation, about 85% of the heme f undergoes pulse-limited photo-oxidation (<100 fs), with the electron acceptor being most probably one of the adjacent aromatic amino acid residues. After charge recombination in 5.3 ps, the residual excess energy is dissipated in 3.6 ps. In a parallel pathway, the remaining 15% of the hemes directly relax from their excited state in 2.5 ps. In contrast to a vast variety of heme-proteins, including the homologous heme c1 from the cytochrome bc1 complex, there is no evidence that heme f photo-dissociates from its axial ligands. Due to its unique binding, with histidine and an unusual tyrosine as axial ligands, the heme f exemplifies a dependence of ultrafast dynamics on the structural environment.
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Affiliation(s)
- Adrien A P Chauvet
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratoire de Spectroscopie Ultrarapide (LSU), ISIC, Faculté des Sciences de Base and Lausanne Centre for Ultrafast Science (LACUS), Station 6, 1015 Lausanne, Switzerland.
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Tietz S, Puthiyaveetil S, Enlow HM, Yarbrough R, Wood M, Semchonok DA, Lowry T, Li Z, Jahns P, Boekema EJ, Lenhert S, Niyogi KK, Kirchhoff H. Functional Implications of Photosystem II Crystal Formation in Photosynthetic Membranes. J Biol Chem 2015; 290:14091-106. [PMID: 25897076 PMCID: PMC4447980 DOI: 10.1074/jbc.m114.619841] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Revised: 04/17/2015] [Indexed: 11/06/2022] Open
Abstract
The structural organization of proteins in biological membranes can affect their function. Photosynthetic thylakoid membranes in chloroplasts have the remarkable ability to change their supramolecular organization between disordered and semicrystalline states. Although the change to the semicrystalline state is known to be triggered by abiotic factors, the functional significance of this protein organization has not yet been understood. Taking advantage of an Arabidopsis thaliana fatty acid desaturase mutant (fad5) that constitutively forms semicrystalline arrays, we systematically test the functional implications of protein crystals in photosynthetic membranes. Here, we show that the change into an ordered state facilitates molecular diffusion of photosynthetic components in crowded thylakoid membranes. The increased mobility of small lipophilic molecules like plastoquinone and xanthophylls has implications for diffusion-dependent electron transport and photoprotective energy-dependent quenching. The mobility of the large photosystem II supercomplexes, however, is impaired, leading to retarded repair of damaged proteins. Our results demonstrate that supramolecular changes into more ordered states have differing impacts on photosynthesis that favor either diffusion-dependent electron transport and photoprotection or protein repair processes, thus fine-tuning the photosynthetic energy conversion.
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Affiliation(s)
- Stefanie Tietz
- From the Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164-6340
| | - Sujith Puthiyaveetil
- From the Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164-6340
| | - Heather M Enlow
- From the Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164-6340
| | - Robert Yarbrough
- From the Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164-6340
| | - Magnus Wood
- From the Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164-6340
| | - Dmitry A Semchonok
- the Electron Microscopy Group, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747AG Groningen, The Netherlands
| | - Troy Lowry
- the Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4370
| | - Zhirong Li
- the Howard Hughes Medical Institute, Department of Plant and Microbial Biology, University of California and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720-3102, and
| | - Peter Jahns
- the Institut für Biochemie der Pflanzen, Heinrich-Heine Universität Düsseldorf, 40225 Düsseldorf, Germany
| | - Egbert J Boekema
- the Electron Microscopy Group, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747AG Groningen, The Netherlands
| | - Steven Lenhert
- the Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4370
| | - Krishna K Niyogi
- the Howard Hughes Medical Institute, Department of Plant and Microbial Biology, University of California and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720-3102, and
| | - Helmut Kirchhoff
- From the Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164-6340,
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Liu J, Chakraborty S, Hosseinzadeh P, Yu Y, Tian S, Petrik I, Bhagi A, Lu Y. Metalloproteins containing cytochrome, iron-sulfur, or copper redox centers. Chem Rev 2014; 114:4366-469. [PMID: 24758379 PMCID: PMC4002152 DOI: 10.1021/cr400479b] [Citation(s) in RCA: 549] [Impact Index Per Article: 54.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Indexed: 02/07/2023]
Affiliation(s)
- Jing Liu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Saumen Chakraborty
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Parisa Hosseinzadeh
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yang Yu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Shiliang Tian
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Igor Petrik
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Ambika Bhagi
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yi Lu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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Zhu XG, Wang Y, Ort DR, Long SP. e-Photosynthesis: a comprehensive dynamic mechanistic model of C3 photosynthesis: from light capture to sucrose synthesis. PLANT, CELL & ENVIRONMENT 2013; 36:1711-27. [PMID: 23072293 DOI: 10.1111/pce.12025] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Photosynthesis is arguably the most researched of all plant processes. A dynamic model of leaf photosynthesis that includes each discrete process from light capture to carbohydrate synthesis, e-photosynthesis, is described. It was developed by linking and extending our previous models of photosystem II (PSII) energy transfer and photosynthetic C3 carbon metabolism to include electron transfer processes around photosystem I (PSI), ion transfer between the lumen and stroma, ATP synthesis and NADP reduction to provide a complete representation. Different regulatory processes linking the light and dark reactions are also included: Rubisco activation via Rubisco activase, pH and xanthophyll cycle-dependent non-photochemical quenching mechanisms, as well as the regulation of enzyme activities via the ferredoxin-theoredoxin system. Although many further feedback and feedforward controls undoubtedly exist, it is shown that e-photosynthesis effectively mimics the typical kinetics of leaf CO₂ uptake, O₂ evolution, chlorophyll fluorescence emission, lumen and stromal pH, and membrane potential following perturbations in light, [CO₂] and [O₂] observed in intact C3 leaves. The model provides a framework for guiding engineering of improved photosynthetic efficiency, for evaluating multiple non-invasive measures used in emerging phenomics facilities, and for quantitative assessment of strengths and weaknesses within the understanding of photosynthesis as an integrated process.
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Affiliation(s)
- Xin-Guang Zhu
- State Key Laboratory of Hybrid Rice, Shanghai Institutes for Biological Sciences, CAS, Shanghai 200031, China.
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12
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Kallas T. Cytochrome b 6 f Complex at the Heart of Energy Transduction and Redox Signaling. PHOTOSYNTHESIS 2012. [DOI: 10.1007/978-94-007-1579-0_21] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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13
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14
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Twigg AI, Baniulis D, Cramer WA, Hendrich MP. EPR detection of an O(2) surrogate bound to heme c(n) of the cytochrome b(6)f complex. J Am Chem Soc 2009; 131:12536-7. [PMID: 19689132 DOI: 10.1021/ja905171c] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The ligand-binding properties of the unique heme c(n) of the cyt b(6)f complex, which is bridged to the heme b(n), are studied with EPR spectroscopy. Despite an open coordination site, high-spin heme c(n) in the oxidized state does not bind typical heme ligands such as cyanide, indicating their inaccessibility to the heme. In the reduced state, heme c(n) binds the O(2) surrogate NO to give a five-coordinate S = (1)/(2) [FeNO](7) complex, indicating that the site is accessible in the reduced state of the protein. The binding of NO implies that the heme c(n) can also bind O(2). Given the significant number of experimentally documented pathways for which a plastoquinol oxidase has been proposed, but the actual oxidase not identified, it is proposed that one of the functions of heme c(n), the only prosthetic group in the electron transport chain with oxidase-like properties, is the putative oxidase.
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Affiliation(s)
- Anna I Twigg
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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15
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Ma F, Chen XB, Sang M, Wang P, Zhang JP, Li LB, Kuang TY. Singlet oxygen formation and chlorophyll a triplet excited state deactivation in the cytochrome b6f complex from Bryopsis corticulans. PHOTOSYNTHESIS RESEARCH 2009; 100:19-28. [PMID: 19333778 DOI: 10.1007/s11120-009-9418-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2008] [Accepted: 03/14/2009] [Indexed: 05/27/2023]
Abstract
We have attempted to investigate the correlation between the detergent-perturbed structural integrity of the Cyt b (6) f complex from the marine green alga Bryopsis corticulans and its photo-protective properties, for which the nonionic detergents n-octyl-beta-D-glucopyranoside (beta-OG) and n-dodecyl-beta-D-maltoside (beta-DM), respectively, were used for the preparation of Cyt b (6) f, and the singlet oxygen ((1)O(2)*) production as well as the triplet excited-state chlorophyll a ((3)Chl a*) formation and deactivation were examined by spectroscopic means. Near-infrared luminescence of (1)O(2)* (approximately 1,270 nm) on photo-irradiation was detected for the beta-OG preparation where the complex is mainly in oligomeric state, but not for the beta-DM one in which the complex exists in dimeric form. Under anaerobic condition, photo-excitation of Chl a in the beta-DM preparation generated (3)Chl a* with a lower quantum yield of Phi(T) approximately 0.02 and a longer lifetime of approximately 600 micros with respect to those as in the case of beta-OG preparation, Phi(T) approximately 0.12 and 200-300 micros. These results prove that the enzymatically active and intact Cyt b (6) f complex on photo-excitation tends to produce little (3)Chl a* or (1)O(2)*, which implies that the pigment-protein assembly of Cyt b (6) f complex per se is crucial for photo-protection.
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Affiliation(s)
- Fei Ma
- Beijing National Laboratory for Molecular Science, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
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16
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Why is it so difficult to construct Qi site mutants in Chlamydomonas reinhardtii? C R Biol 2008; 331:510-7. [DOI: 10.1016/j.crvi.2008.04.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2007] [Revised: 04/02/2008] [Accepted: 04/03/2008] [Indexed: 11/18/2022]
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de Lacroix de Lavalette A, Finazzi G, Zito F. b6f-Associated Chlorophyll: Structural and Dynamic Contribution to the Different Cytochrome Functions. Biochemistry 2008; 47:5259-65. [DOI: 10.1021/bi800179b] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Agnès de Lacroix de Lavalette
- UMR 7099, CNRS and Université Paris-7, and UMR 7141, CNRS and Université Paris-6, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, F-75005 Paris, France
| | - Giovanni Finazzi
- UMR 7099, CNRS and Université Paris-7, and UMR 7141, CNRS and Université Paris-6, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, F-75005 Paris, France
| | - Francesca Zito
- UMR 7099, CNRS and Université Paris-7, and UMR 7141, CNRS and Université Paris-6, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, F-75005 Paris, France
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18
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Seddiki N, Meunier B, Lemesle-Meunier D, Brasseur G. Is Cytochrome b Glutamic Acid 272 a Quinol Binding Residue in the bc1 Complex of Saccharomyces cerevisiae? Biochemistry 2008; 47:2357-68. [DOI: 10.1021/bi701905a] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Nadir Seddiki
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille cedex 20, France, and Centre de Génétique Moléculaire, CNRS, UPR 2167, Gif-sur-Yvette, F-91198, France
| | - Brigitte Meunier
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille cedex 20, France, and Centre de Génétique Moléculaire, CNRS, UPR 2167, Gif-sur-Yvette, F-91198, France
| | - Danielle Lemesle-Meunier
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille cedex 20, France, and Centre de Génétique Moléculaire, CNRS, UPR 2167, Gif-sur-Yvette, F-91198, France
| | - Gaël Brasseur
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille cedex 20, France, and Centre de Génétique Moléculaire, CNRS, UPR 2167, Gif-sur-Yvette, F-91198, France
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19
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Hulsker R, Baranova MV, Bullerjahn GS, Ubbink M. Dynamics in the transient complex of plastocyanin-cytochrome f from Prochlorothrix hollandica. J Am Chem Soc 2008; 130:1985-91. [PMID: 18201089 DOI: 10.1021/ja077453p] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
The nature of transient protein complexes can range from a highly dynamic ensemble of orientations to a single well-defined state. This represents variation in the equilibrium between the encounter and final, functional state. The transient complex between plastocyanin (Pc) and cytochrome f (cytf) of the cyanobacterium Prochlorothrix hollandica was characterized by NMR spectroscopy. Intermolecular pseudocontact shifts and chemical shift perturbations were used as restraints in docking calculations to determine the structure of the wild-type Pc-cytf complex. The orientation of Pc is similar to orientations found in Pc-cytf complexes from other sources. Electrostatics seems to play a modest role in complex formation. A large variability in the ensemble of lowest energy structures indicates a dynamic nature of the complex. Two unusual hydrophobic patch residues in Pc have been mutated to the residues found in other plastocyanins (Y12G/P14L). The binding constants are similar for the complexes of cytf with wild-type Pc and mutant Pc, but the chemical shift perturbations are smaller for the complex with mutant Pc. Docking calculations for the Y12G/P14L Pc-cytf complex did not produce a converged ensemble of structures. Simulations of the dynamics were performed using the observed averaged NMR parameters as input. The results indicate a surprisingly large amplitude of mobility of Y12G/P14L Pc within the complex. It is concluded that the double mutation shifts the complex further from the well-defined toward the encounter state.
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Affiliation(s)
- Rinske Hulsker
- Leiden Institute of Chemistry, Leiden University, Gorlaeus Laboratories, P.O. Box 9502, 2300 RA Leiden, The Netherlands
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20
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Starita-Geribaldi M, Thebault P, Taffin de Givenchy E, Guittard F, Geribaldi S. 2-DE using hemi-fluorinated surfactants. Electrophoresis 2007; 28:2489-97. [PMID: 17577887 DOI: 10.1002/elps.200600598] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The synthesis of hemi-fluorinated zwitterionic surfactants was realized and assessed for 2-DE, a powerful separation method for proteomic analysis. These new fluorinated amidosulfobetaine (FASB-p,m) were compared to their hydrocarbon counterparts amidosulfobetaine (ASB-n) characterized by a hydrophilic polar head, a hydrophobic and lipophilic tail, and an amido group as connector. The tail of these FASB surfactants was in part fluorinated resulting in the modulation of its lipophilicity (or oleophobicity). Their effect on the red blood cell (RBC) membrane showed a specific solubilization depending on the length of the hydrophobic part. A large number of polypeptide spots appeared in the 2-DE patterns by using FASB-p,m. The oleophobic character of these surfactants was confirmed by the fact that Band 3, a highly hydrophobic transmembrane protein, was not solubilized by these fluorinated structures. The corresponding pellet was very rich in Band 3 and could then be solubilized by using a strong detergent such as amidosulfobetaine with an alkyl tail containing 14 carbon atoms (ASB-14). Thus, these hemi-fluorinated surfactants appeared as powerful tools when used at the first step of a two-step solubilization strategy using a hydrocarbon homologous surfactant in the second step.
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Affiliation(s)
- Mireille Starita-Geribaldi
- Connexines et Prolifération Germinale: Physiopathologie Cellulaire et Moléculaire (INSERM U670), UFR de Médecine, Université de Nice Sophia-Antipolis, Nice, France.
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21
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Tremmel IG, Weis E, Farquhar GD. Macromolecular crowding and its influence on possible reaction mechanisms in photosynthetic electron flow. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2007; 1767:353-61. [PMID: 17445761 DOI: 10.1016/j.bbabio.2007.03.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2006] [Revised: 02/27/2007] [Accepted: 03/01/2007] [Indexed: 11/15/2022]
Abstract
The diffusion of plastoquinol and its binding to the Qo site of the cyt bf complex in the course of photosynthetic electron transport was studied by following the sigmoidal flash-induced re-reduction kinetics of P700 after previous oxidation of the intersystem electron carriers. The data resulting from these experiments were matched with a simulation of electron transport using Monte Carlo techniques. The simulation was able to account for the experimental observations. Two different extreme cases of reaction mechanism at the Qo site were compared: a diffusion limited collisional mechanism and a non-diffusion limited tight binding mechanism. Assuming a tight binding mechanism led to best matches due to the high protein density in thylakoids. The varied parameters resulted in values well within the range of published data. The results emphasise the importance of structural characteristics of thylakoids in models of electron transport.
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Affiliation(s)
- I G Tremmel
- Max-Planck-Institute for Biophysical Chemistry, Theoretical and Computational Biophysics Department, Am Fassberg 11, D-37077 Goettingen, Germany.
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22
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Laisk A, Eichelmann H, Oja V. C3 photosynthesis in silico. PHOTOSYNTHESIS RESEARCH 2006; 90:45-66. [PMID: 17131095 DOI: 10.1007/s11120-006-9109-1] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2006] [Accepted: 09/26/2006] [Indexed: 05/12/2023]
Abstract
A computer model comprising light reactions, electron-proton transport, enzymatic reactions, and regulatory functions of C3 photosynthesis has been developed as a system of differential budget equations for intermediate compounds. The emphasis is on electron transport through PSII and PSI and on the modeling of Chl fluorescence and 810 nm absorptance signals. Non-photochemical quenching of PSII excitation is controlled by lumenal pH. Alternative electron transport is modeled as the Mehler type O2 reduction plus the malate-oxaloacetate shuttle based on the chloroplast malate dehydrogenase. Carbon reduction enzymes are redox-controlled by the ferredoxin-thioredoxin system, sucrose synthesis is controlled by the fructose 2,6-bisphosphate inhibition of cytosolic FBPase, and starch synthesis is controlled by ADP-glucose pyrophosphorylase. Photorespiratory glycolate pathway is included in an integrated way, sufficient to reproduce steady-state rates of photorespiration. Rate-equations are designed on principles of multisubstrate-multiproduct enzyme kinetics. The parameters of the model were adopted from literature or were estimated from fitting the photosynthetic rate and pool sizes to experimental data. The model provided good simulations for steady-state photosynthesis, Chl fluorescence, and 810 nm transmittance signals under varying light, CO2 and O2 concentrations, as well as for the transients of post-illumination CO2 uptake, Chl fluorescence induction and the 810 nm signal. The modeling shows that the present understanding of photosynthesis incorporated in the model is basically correct, but still insufficient to reproduce the dark-light induction of photosynthesis, the time kinetics of non-photochemical quenching, 'photosynthetic control' of plastoquinone oxidation, cyclic electron flow around PSI, oscillations in photosynthesis. The model may find application for predicting the results of gene transformations, the analysis of kinetic experimental data, the training of students.
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Affiliation(s)
- Agu Laisk
- Institute for Molecular and Cell Biology, Tartu University, 23 Riia st., Tartu, 51010, Estonia.
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23
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Adams KL, Tsoi S, Yan J, Durbin SM, Ramdas AK, Cramer WA, Sturhahn W, Alp EE, Schulz C. Fe vibrational spectroscopy of myoglobin and cytochrome f. J Phys Chem B 2006; 110:530-6. [PMID: 16471565 DOI: 10.1021/jp053440r] [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] [Indexed: 11/29/2022]
Abstract
The Fe vibrational density of states (VDOS) has been determined for the heme proteins deoxymyoglobin, metmyoglobin, and cytochrome f in the oxidized and reduced states, using nuclear resonance vibrational spectroscopy (NRVS). For cytochrome f in particular, the NRVS spectrum is compared with multiwavelength resonance Raman spectra to identify those Raman modes with significant Fe displacement. Modes not seen by Raman due to optical selection rules appear in the NRVS spectrum. The mean Fe force constant extracted from the VDOS illustrates how Fe dynamics varies among these four monoheme proteins, and is correlated with oxidation and spin state trends seen in model heme compounds. The protein's contribution to Fe motion is dominant at low frequencies, where coupling to the backbone tightly constrains Fe displacements in cytochrome f, in contrast to enhanced heme flexibility in myoglobin.
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Affiliation(s)
- Kristl L Adams
- Department of Physics, Purdue University, West Lafayette, Indiana 47907, USA
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24
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Albarrán C, Navarro JA, Molina-Heredia FP, Murdoch PDS, De la Rosa MA, Hervás M. Laser flash-induced kinetic analysis of cytochrome f oxidation by wild-type and mutant plastocyanin from the cyanobacterium Nostoc sp. PCC 7119. Biochemistry 2005; 44:11601-7. [PMID: 16114897 DOI: 10.1021/bi050917g] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Oxidation of the soluble, truncated form of cytochrome f by wild-type and mutant species of plastocyanin has been analyzed by laser flash absorption spectroscopy in the cyanobacterium Nostoc (formerly, Anabaena) sp. PCC 7119. At low ionic strengths, the apparent electron transfer rate constant of cytochrome f oxidation by wild-type plastocyanin is 1.34 x 10(4) s(-)(1), a value much larger than those determined for the same proteins from other organisms. Upon site-directed mutagenesis of specific residues at the plastocyanin interaction area, the rate constant decreases in all cases yet to varying extents. The only exception is the D54K variant, which exhibits a higher reactivity toward cytochrome f. In most cases, the reaction rate constant decreases monotonically with an increase in ionic strength. The observed changes in the reaction mechanism and rate constants are in agreement with the location of the mutated residues at the interface area, as well as with the peculiar orientation of the two partners within the Nostoc plastocyanin-cytochrome f transient complex, whose NMR structure has been determined recently. Furthermore, the experimental data herein reported match well the kinetic behavior exhibited by the same set of plastocyanin mutants when acting as donors of electrons to photosystem I [Molina-Heredia, F. P., et al. (2001) J. Biol. Chem. 276, 601-605], thus indicating that the copper protein uses the same surface areas-one hydrophobic and the other electrostatic-to interact with both cytochrome f and photosystem I.
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Affiliation(s)
- Cristina Albarrán
- Instituto de Bioquímica Vegetal y Fotosíntesis, Centro de Investigaciones Científicas Isla de la Cartuja, Universidad de Sevilla y Consejo Superior de Investigaciones Científicas, Sevilla, Spain
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25
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Mulkidjanian AY. Ubiquinol oxidation in the cytochrome bc1 complex: Reaction mechanism and prevention of short-circuiting. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2005; 1709:5-34. [PMID: 16005845 DOI: 10.1016/j.bbabio.2005.03.009] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2004] [Revised: 12/01/2004] [Accepted: 03/22/2005] [Indexed: 11/26/2022]
Abstract
This review is focused on the mechanism of ubiquinol oxidation by the cytochrome bc1 complex (bc1). This integral membrane complex serves as a "hub" in the vast majority of electron transfer chains. The bc1 oxidizes a ubiquinol molecule to ubiquinone by a unique "bifurcated" reaction where the two released electrons go to different acceptors: one is accepted by the mobile redox active domain of the [2Fe-2S] iron-sulfur Rieske protein (FeS protein) and the other goes to cytochrome b. The nature of intermediates in this reaction remains unclear. It is also debatable how the enzyme prevents short-circuiting that could happen if both electrons escape to the FeS protein. Here, I consider a reaction mechanism that (i) agrees with the available experimental data, (ii) entails three traits preventing the short-circuiting in bc1, and (iii) exploits the evident structural similarity of the ubiquinone binding sites in the bc1 and the bacterial photosynthetic reaction center (RC). Based on the latter congruence, it is suggested that the reaction route of ubiquinol oxidation by bc1 is a reversal of that leading to the ubiquinol formation in the RC. The rate-limiting step of ubiquinol oxidation is then the re-location of a ubiquinol molecule from its stand-by site within cytochrome b into a catalytic site, which is formed only transiently, after docking of the mobile redox domain of the FeS protein to cytochrome b. In the catalytic site, the quinone ring is stabilized by Glu-272 of cytochrome b and His-161 of the FeS protein. The short circuiting is prevented as long as: (i) the formed semiquinone anion remains bound to the reduced FeS domain and impedes its undocking, so that the second electron is forced to go to cytochrome b; (ii) even after ubiquinol is fully oxidized, the reduced FeS domain remains docked to cytochrome b until electron(s) pass through cytochrome b; (iii) if cytochrome b becomes (over)reduced, the binding and oxidation of further ubiquinol molecules is hampered; the reason is that the Glu-272 residue is turned towards the reduced hemes of cytochrome b and is protonated to stabilize the surplus negative charge; in this state, this residue cannot participate in the binding/stabilization of a ubiquinol molecule.
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Affiliation(s)
- Armen Y Mulkidjanian
- Max Planck Institute of Biophysics, Department of Biophysical Chemistry, Max-von-Laue-Str. 3, D-60438 Frankfurt-am-Main, Germany.
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26
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Laisk A, Eichelmann H, Oja V, Peterson RB. Control of cytochrome b6f at low and high light intensity and cyclic electron transport in leaves. BIOCHIMICA ET BIOPHYSICA ACTA 2005; 1708:79-90. [PMID: 15949986 DOI: 10.1016/j.bbabio.2005.01.007] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2004] [Revised: 01/11/2005] [Accepted: 01/20/2005] [Indexed: 10/25/2022]
Abstract
The light-dependent control of photosynthetic electron transport from plastoquinol (PQH(2)) through the cytochrome b(6)f complex (Cyt b(6)f) to plastocyanin (PC) and P700 (the donor pigment of Photosystem I, PSI) was investigated in laboratory-grown Helianthus annuus L., Nicotiana tabaccum L., and naturally-grown Solidago virgaurea L., Betula pendula Roth, and Tilia cordata P. Mill. leaves. Steady-state illumination was interrupted (light-dark transient) or a high-intensity 10 ms light pulse was applied to reduce PQ and oxidise PC and P700 (pulse-dark transient) and the following re-reduction of P700(+) and PC(+) was recorded as leaf transmission measured differentially at 810-950 nm. The signal was deconvoluted into PC(+) and P700(+) components by oxidative (far-red) titration (V. Oja et al., Photosynth. Res. 78 (2003) 1-15) and the PSI density was determined by reductive titration using single-turnover flashes (V. Oja et al., Biochim. Biophys. Acta 1658 (2004) 225-234). These innovations allowed the definition of the full light response curves of electron transport rate through Cyt b(6)f to the PSI donors. A significant down-regulation of Cyt b(6)f maximum turnover rate was discovered at low light intensities, which relaxed at medium light intensities, and strengthened again at saturating irradiances. We explain the low-light regulation of Cyt b(6)f in terms of inactivation of carbon reduction cycle enzymes which increases flux resistance. Cyclic electron transport around PSI was measured as the difference between PSI electron transport (determined from the light-dark transient) and PSII electron transport determined from chlorophyll fluorescence. Cyclic e(-) transport was not detected at limiting light intensities. At saturating light the cyclic electron transport was present in some, but not all, leaves. We explain variations in the magnitude of cyclic electron flow around PSI as resulting from the variable rate of non-photosynthetic ATP-consuming processes in the chloroplast, not as a principle process that corrects imbalances in ATP/NADPH stoichiometry during photosynthesis.
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Affiliation(s)
- Agu Laisk
- Tartu Ulikooli Molekulaar-ja Rakubioloogia Instituut, Riia tn. 23, Tartu, 51010, Estonia.
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27
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Dashdorj N, Zhang H, Kim H, Yan J, Cramer WA, Savikhin S. The single chlorophyll a molecule in the cytochrome b6f complex: unusual optical properties protect the complex against singlet oxygen. Biophys J 2005; 88:4178-87. [PMID: 15778449 PMCID: PMC1305648 DOI: 10.1529/biophysj.104.058693] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2004] [Accepted: 03/16/2005] [Indexed: 11/18/2022] Open
Abstract
The cytochrome b(6)f complex of oxygenic photosynthesis mediates electron transfer between the reaction centers of photosystems I and II and facilitates coupled proton translocation across the membrane. High-resolution x-ray crystallographic structures (Kurisu et al., 2003; Stroebel et al., 2003) of the cytochrome b(6)f complex unambiguously show that a Chl a molecule is an intrinsic component of the cytochrome b(6)f complex. Although the functional role of this Chl a is presently unclear (Kuhlbrandt, 2003), an excited Chl a molecule is known to produce toxic singlet oxygen as the result of energy transfer from the excited triplet state of the Chl a to oxygen molecules. To prevent singlet oxygen formation in light-harvesting complexes, a carotenoid is typically positioned within approximately 4 A of the Chl a molecule, effectively quenching the triplet excited state of the Chl a. However, in the cytochrome b(6)f complex, the beta-carotene is too far (> or =14 Angstroms) from the Chl a for effective quenching of the Chl a triplet excited state. In this study, we propose that in this complex, the protection is at least partly realized through special arrangement of the local protein structure, which shortens the singlet excited state lifetime of the Chl a by a factor of 20-25 and thus significantly reduces the formation of the Chl a triplet state. Based on optical ultrafast absorption difference experiments and structure-based calculations, it is proposed that the Chl a singlet excited state lifetime is shortened due to electron exchange transfer with the nearby tyrosine residue. To our knowledge, this kind of protection mechanism against singlet oxygen has not yet been reported for any other chlorophyll-containing protein complex. It is also reported that the Chl a molecule in the cytochrome b(6)f complex does not change orientation in its excited state.
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28
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Nelson ME, Finazzi G, Wang QJ, Middleton-Zarka KA, Whitmarsh J, Kallas T. Cytochrome b6 Arginine 214 of Synechococcus sp. PCC 7002, a Key Residue for Quinone-reductase Site Function and Turnover of the Cytochrome bf Complex. J Biol Chem 2005; 280:10395-402. [PMID: 15632120 DOI: 10.1074/jbc.m410948200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Quinone-reductase (Q(i)) domains of cyanobacterial/chloroplast cytochrome bf and bacterial/mitochondrial bc complexes differ markedly, and the cytochrome bf Q(i) site mechanism remains largely enigmatic. To investigate the bf Q(i) domain, we constructed the mutation R214H, which substitutes histidine for a conserved arginine in the cytochrome b(6) polypeptide of the cyanobacterium Synechococcus sp. SPCC 7002. At high light intensity, the R214H mutant grew approximately 2.5-fold more slowly than the wild type. Slower growth arose from correspondingly slower overall turnover of the bf complex. Specifically, as shown in single flash turnover experiments of cytochrome b(6) reduction and oxidation, the R214H mutation partially blocked electron transfer to the Q(i) site, mimicking the effect of the Q(i) site inhibitor 2-N-4-hydroxyquinoline-N-oxide. The kinetics of cytochrome b(6) oxidation were largely unaffected by hydrogen-deuterium exchange in the mutant but were slowed considerably in the wild type. This suggests that although protonation events influenced the kinetics of cytochrome b(6) oxidation at the Q(i) site in the wild type, electron flow limited this reaction in the R214H mutant. Redox titration of membranes revealed midpoint potentials (E(m,7)) of the two b hemes similar to those in the wild type. Our data define cytochrome b(6) Arg(214) as a key residue for Q(i) site catalysis and turnover of the cytochrome bf complex. In the recent cytochrome bf structures, Arg(214) lies near the Q(i) pocket and the newly discovered c(i) or x heme. We propose a model for Q(i) site function and a role for Arg(214) in plastoquinone binding.
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Affiliation(s)
- Matthew E Nelson
- Department of Biology and Microbiology, University of Wisconsin-Oshkosh, Oshkosh, Wisconsin 54901, USA
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29
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Tremmel IG, Weis E, Farquhar GD. The influence of protein-protein interactions on the organization of proteins within thylakoid membranes. Biophys J 2005; 88:2650-60. [PMID: 15665125 PMCID: PMC1305361 DOI: 10.1529/biophysj.104.045666] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The influence of attractive protein-protein interactions on the organization of photosynthetic proteins within the thylakoid membrane was investigated. Protein-protein interactions were simulated using Monte Carlo techniques and the influence of different interaction energies was examined. It was found that weak interactions led to protein clusters whereas strong interactions led to ramified chains. An optimum curve for the relationship between interaction energy and the number of contact sites emerged. With increasing particle densities the effect decreased. In a mixture of interacting and noninteracting particles the distance between the noninteracting particles was increased and there seemed to be much more free space around them. In thylakoids, this could lead to a more homogeneous distribution of the noninteracting but rate-limiting cytochrome bf complexes. Due to the increased free space between cytochrome bf, obstruction of binding sites--occurring unavoidably in a random distribution--may be drastically reduced. Furthermore, protein-protein interactions in thylakoids may lead to a decrease in plastoquinone diffusion.
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Affiliation(s)
- I G Tremmel
- Environmental Biology Group, Research School of Biological Sciences, Australian National University, Canberra, Australia.
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30
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Abstract
Oxygenic photosynthesis is the principal producer of both oxygen and organic matter on earth. The primary step in this process - the conversion of sunlight into chemical energy - is driven by four, multisubunit, membrane-protein complexes that are known as photosystem I, photosystem II, cytochrome b(6)f and F-ATPase. Structural insights into these complexes are now providing a framework for the exploration not only of energy and electron transfer, but also of the evolutionary forces that shaped the photosynthetic apparatus.
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Affiliation(s)
- Nathan Nelson
- Department of Biochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
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31
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Richter M, Daufenbach J, Drebing S, Vucetic V, Nguyen DT. Light-induced proton slip and proton leak at the thylakoid membrane. JOURNAL OF PLANT PHYSIOLOGY 2004; 161:1325-1337. [PMID: 15658803 DOI: 10.1016/j.jplph.2004.03.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A treatment of leaves of Spinacia oleracea L. with light or with the thiol reagent dithiothreitol in the dark led to partly uncoupled thylakoids. After induction in intact leaves, the partial uncoupling was irreversible at the level of isolated thylakoids. We distinguish between uncoupling by proton slip, which means a decrease of the H+/e(-) -ratio due to less efficient proton pumping, and proton leak as defined by enhanced kinetics of proton efflux. Proton slip and proton leak made about equal contributions to the total uncoupling. The enhanced proton efflux kinetics corresponded to reduction of subunit CF1-gamma of the ATP synthase as shown by fluorescence labeling of thylakoid proteins with the sulfhydryl probe 5-iodoacetamido fluorescein. The maximum value of the fraction of reduced CF1-gamma was only 36%, which indicates that in vivo the reduction of CF1-gamma could be limited by fast reoxidation and/or restricted accessibility of CF1-gamma to thioredoxin. Measurements of the ratio ATP/2e indicated that only the uncoupling related to less efficient proton pumping led to a decrease in the ATP yield.
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Affiliation(s)
- Michael Richter
- Institut für Allgemeine Botanik, Johannes Gutenberg Universität, D-55099 Mainz, Germany.
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32
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Gross EL. A Brownian dynamics study of the interaction of Phormidium laminosum plastocyanin with Phormidium laminosum cytochrome f. Biophys J 2004; 87:2043-59. [PMID: 15345580 PMCID: PMC1304607 DOI: 10.1529/biophysj.103.038497] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2003] [Accepted: 05/21/2004] [Indexed: 11/18/2022] Open
Abstract
The interaction of Phormidium laminosum plastocyanin (PC) with P. laminosum cytochrome f (cyt f) was studied using Brownian dynamics (BD) simulations. Few complexes and a low rate of electron transfer were observed for wild-type PC. Increasing the positive electrostatic field on PC by the addition of a Zn(2+) ion in the neighborhood of D44 and D45 on PC (as found in crystal structure of plastocyanin) increased the number of complexes formed and the calculated rates of electron transfer as did PC mutations D44A, D45A, E54A, and E57A. Mutations of charged residues on Phormidium PC and Phormidium cyt f were used to map binding sites on both proteins. In both the presence and absence of the Zn(2+) ion, the following residues on PC interact with cyt f: D44, D45, K6, D79, R93, and K100 that lie in a patch just below H92 and Y88 and D10, E17, and E70 located on the upper portion of the PC molecule. In the absence of the Zn(2+) ion, K6 and K35 on the top of the PC molecule also interact with cyt f. Cyt f residues involved in binding PC, in the absence of the Zn(2+) ion, include E165, D187, and D188 that are located on the small domain of cyt f. The orientation of PC in the complexes was quite random in accordance with NMR results. In the presence of the Zn(2+) ion, K53 and E54 in the lower patch of the PC molecule also interact with cyt f and PC interacts with E86, E95, and E123 on the large domain of cyt f. Also, the orientation of PC in the complexes was much more uniform than in the absence of the Zn(2+) ion. The difference may be due to both the larger electrostatic field and the greater asymmetry of the charge distribution on PC observed in the presence of the Zn(2+) ion. Hydrophobic interactions were also observed suggesting a model of cyt f-PC interactions in which electrostatic forces bring the two molecules together but hydrophobic interactions participate in stabilizing the final electron-transfer-active dock.
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Affiliation(s)
- Elizabeth L Gross
- Department of Biochemistry, The Ohio State University, Columbus, Ohio 34210, USA.
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Cramer WA, Zhang H, Yan J, Kurisu G, Smith JL. Evolution of photosynthesis: time-independent structure of the cytochrome b6f complex. Biochemistry 2004; 43:5921-9. [PMID: 15147175 DOI: 10.1021/bi049444o] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Structures of the cytochrome b(6)f complex obtained from the thermophilic cyanobacterium Mastigocladus laminosus and the green alga Chlamydomonas reinhardtii, whose appearance in evolution is separated by 10(9) years, are almost identical. Two monomers with a molecular weight of 110,000, containing eight subunits and seven natural prosthetic groups, are separated by a large lipid-containing "quinone exchange cavity". A unique heme, heme x, that is five-coordinated and high-spin, with no strong field ligand, occupies a position close to intramembrane heme b(n). This position is filled by the n-side bound quinone, Q(n), in the cytochrome bc(1) complex of the mitochondrial respiratory chain. The structure and position of heme x suggest that it could function in ferredoxin-dependent cyclic electron transport as well as being an intermediate in a quinone cycle mechanism for electron and proton transfer. The significant differences between the cyanobacterial and algal structures are as follows. (i) On the n-side, a plastoquinone molecule is present in the quinone exchange cavity in the cyanobacterial complex, and a sulfolipid is bound in the algal complex at a position corresponding to a synthetic DOPC lipid molecule in the cyanobacterial complex. (ii) On the p-side, in both complexes a quinone analogue inhibitor, TDS, passes through a portal that separates the large cavity from a niche containing the Fe(2)S(2) cluster. However, in the cyanobacterial complex, TDS is in an orientation that is the opposite of its position in the algal structure and bc(1) complexes, so its headgroup in the M. laminosus structure is 20 A from the Fe(2)S(2) cluster.
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Affiliation(s)
- William A Cramer
- Department of Biological Sciences, Lilly Hall of Life Sciences, 915 West State Street, Purdue University, West Lafayette, Indiana 47907-2054, USA.
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de Vitry C, Desbois A, Redeker V, Zito F, Wollman FA. Biochemical and spectroscopic characterization of the covalent binding of heme to cytochrome b6. Biochemistry 2004; 43:3956-68. [PMID: 15049703 DOI: 10.1021/bi036093p] [Citation(s) in RCA: 35] [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 three-dimensional structure of the cytochrome b(6)f complex disclosed the unexpected presence of a new heme c(i) [Stroebel, D., Choquet, Y., Popot, J.-L., and Picot, D. (2003) Nature 426, 413-418; Kurisu, G., Zhang, H., Smith, J. L., and Cramer, W. A. (2003) Science 302, 1009-1014]. Here we present a biochemical, spectroscopic, and mutagenesis study of this unusual heme binding in Chlamydomonas reinhardtii. As predicted by the structure data, we identify a Cys(35)-containing proteolytic fragment (Tyr(25)-Lys(111)) from cytochrome b(6) as a peptide that covalently binds a heme. Resonance Raman spectra of cyt b(6)f complexes show particular frequencies in nu(2), nu(3), nu(4), and nu(8) regions that identify this extra heme as a ferrous c'-like heme under a five-coordinated high-spin state. The set of frequencies is consistent with a coordination by either a water molecule or a hydroxide ion. Other changes in resonance Raman bands, observed in the mid- and low-frequency regions, point to a modification in conformation and/or environment of at least one b heme methyl and/or propionate group. Site-directed mutagenesis of apocytochrome b(6), leading to a Cys(35)Val substitution, generates Chlamydomonas strains that are unable to assemble cytochrome b(6)f complexes. On the basis of the mutant phenotype, we discuss the participation, in the covalent binding of heme c(i), of the nuclear CCB factors that we identified previously as controlling the apo to holo conversion of cytochrome b(6) [Kuras, R., de Vitry, C., Choquet, Y., Girard-Bascou, J., Culler, D., Büschlen, S., Merchant, S., and Wollman, F.-A. (1997) J. Biol. Chem. 272, 32427-32435].
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Affiliation(s)
- Catherine de Vitry
- Physiologie Membranaire et Moléculaire du Chloroplaste CNRS UPR 1261, Institut de Biologie Physico-Chimique CNRS FRC 550, 13 Rue Pierre et Marie Curie, 75005 Paris, France.
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Cooley JW, Roberts AG, Bowman MK, Kramer DM, Daldal F. The raised midpoint potential of the [2Fe2S] cluster of cytochrome bc1 is mediated by both the Qo site occupants and the head domain position of the Fe-S protein subunit. Biochemistry 2004; 43:2217-27. [PMID: 14979718 DOI: 10.1021/bi035938u] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have previously reported that mutant strains of Rhodobacter capsulatus that have alanine insertions (+nAla mutants) in the hinge region of the iron sulfur (Fe-S) containing subunit of the bc(1) complex have increased redox midpoint potentials (E(m)) for their [2Fe2S] clusters. The alteration of the E(m) in these strains, which contain mutations far from the metal binding site, implied that the local environment of the metal center is indirectly altered by a change in the interaction of this subunit with the hydroquinone oxidizing (Q(o)) site [Darrouzet, E., Valkova-Valchanova, M., and Daldal, F. (2002) J. Biol. Chem. 277, 3464-3470]. Subsequently, the E(m) changes have been proposed to be predominantly due to a stronger or more stabilized hydrogen bonding between the reduced [2Fe2S] cluster and the Q(o) site inhabitant ubiquinone (Q) [Shinkarev, V. P., Kolling, D. R. J., Miller, T. J., and Crofts, A. R. (2002) Biochemistry 41, 14372-14382]. To further investigate this issue, Fe-S protein-Q interactions were monitored by electron paramagnetic resonance (EPR) spectroscopy and the findings indicated that the wild type and mutant proteins interactions with Q are similar. Moreover, when the Q(pool) was chemically depleted, the E(m) of the [2Fe2S] cluster in mutant bc(1) complexes remained more positive than a similarly treated native enzyme (e.g., the [2Fe2S] E(m) of the +2Ala mutant was 55 mV more positive than the wild type). These data suggest that the increased E(m) of the [2Fe2S] cluster in the +nAla mutants is in part due to the cluster's interaction with Q, and in part to additional factors that are independent of hydrogen bonding to Q. One such factor, the possibility of a different position of the Fe-S at the Q(o) site of the mutant proteins versus the native enzyme, was addressed by determining the orientation of the [2Fe2S] cluster in the membrane using EPR spectroscopy. In the case of the +2Ala mutant, the [2Fe2S] cluster orientation in the absence of inhibitor is different than that seen in the native enzyme. However, the +2Ala mutant cluster shared a similar orientation with the native enzyme when both samples were exposed to either stigmatellin or myxothiazol. In addition, Q(pool) extracted membranes of +2Ala mutant exhibited fewer overall orientations, with the predominant one being more similar to that observed in the non-Q-depleted membranes of the +2Ala mutant than the Q-depleted membranes of a wild-type strain. Therefore, additional component(s) that are independent of Q(o) site inhabitants and that originate from the newly observed orientations of the [2Fe2S] clusters in the +nAla mutants also contribute to the increased midpoint potentials of their [2Fe2S] clusters. While the molecular basis of these components remains to be determined, salient implications of these findings in terms of Q(o) site catalysis are discussed.
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Affiliation(s)
- Jason W Cooley
- Department of Biology, Institute for Plant Sciences, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018, USA
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Brasseur G, Lemesle-Meunier D, Reinaud F, Meunier B. QO Site Deficiency Can Be Compensated by Extragenic Mutations in the Hinge Region of the Iron-Sulfur Protein in the bc1 Complex of Saccharomyces cerevisiae. J Biol Chem 2004; 279:24203-11. [PMID: 15039445 DOI: 10.1074/jbc.m311576200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mitochondrial bc(1) complex catalyzes the oxidation of ubiquinol and the reduction of cytochrome (cyt) c. The cyt b mutation A144F has been introduced in yeast by the biolistic method. This residue is located in the cyt b cd(1) amphipathic helix in the quinol-oxidizing (Q(O)) site. The resulting mutant was respiration-deficient and was affected in the quinol binding and electron transfer rates at the Q(O) site. An intragenic suppressor mutation was selected (A144F+F179L) that partially alleviated the defect of quinol oxidation of the original mutant A144F. The suppressor mutation F179L, located at less than 4 A from A144F, is likely to compensate directly the steric hindrance caused by phenylalanine at position 144. A second set of suppressor mutations was obtained, which also partially restored the quinol oxidation activity of the bc(1) complex. They were located about 20 A from A144F in the hinge region of the iron-sulfur protein (ISP) between residues 85 and 92. This flexible region is crucial for the movement of the ISP between cyt b and cyt c(1) during enzyme turnover. Our results suggested that the compensatory effect of the mutations in ISP was due to the repositioning of this subunit on cyt b during quinol oxidation. This genetic and biochemical study thus revealed the close interaction between the cyt b cd(1) helix in the quinol-oxidizing Q(O) site and the ISP via the flexible hinge region and that fine-tuning of the Q(O) site catalysis can be achieved by subtle changes in the linker domain of the ISP.
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Affiliation(s)
- Gaël Brasseur
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France.
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Sujak A, Drepper F, Haehnel W. Spectroscopic studies on electron transfer between plastocyanin and cytochrome b6f complex. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2004; 74:135-43. [PMID: 15157909 DOI: 10.1016/j.jphotobiol.2004.03.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2003] [Revised: 03/08/2004] [Accepted: 03/22/2004] [Indexed: 10/26/2022]
Abstract
This paper reports the results of the research on the interaction between the highly active cytochrome b(6)f complex and plastocyanin, both isolated from the same source - spinachia oleracea plants. An equilibrium constant K between the cytochrome f of the cytochrome b(6)f complex and plastocyanin has been estimated by two independent spectroscopic techniques: steady-state absorption spectroscopy and stopped-flow. The second-order rate constants k2 for forward and backward electron transfer between cytochrome f and plastocyanin have been found between 1.4-2 x 10(7) and 8-10 x 10(6) M(-1)s(-1), respectively, giving the value of an equilibrium constant of about 2+/-0.4 or a difference in redox potential between plastocyanin and cytochrome f of cytochrome b(6)f complex of ca. 17 mV. The value of K=1.7+/-0.3 has been estimated from steady-state experiments in which the initial and final concentrations of participating components after mixing have been estimated via differential spectra analysis or spectra deconvolution. We propose a method of evaluation of the final plastocyanin concentration after the electron transfer reaction between cytochrome bf complex and plastocyanin that overcomes the interference by the strong chlorophyll absorption in the spectral region where oxidised plastocyanin has its low extinction absorption band. The data from both experiments, in the system devoid of quinol being the electron donor to cytochrome b(6), suggest that in case of electron transfer from cytochrome f to plastocyanin electron transfer can either bypass cytochrome f or the Rieske iron-sulfur protein can be reduced prior to its movement to the quinol binding site of cytochrome b(6). The role of the Rieske protein in forward and backward electron transfer reactions is discussed.
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Affiliation(s)
- A Sujak
- Department of Plant Biochemistry, Freiburg University, Schänzlestrasse 1, Freiburg 79104, Germany.
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38
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Abstract
The bc1 complexes are intrinsic membrane proteins that catalyze the oxidation of ubihydroquinone and the reduction of cytochrome c in mitochondrial respiratory chains and bacterial photosynthetic and respiratory chains. The bc1 complex operates through a Q-cycle mechanism that couples electron transfer to generation of the proton gradient that drives ATP synthesis. Genetic defects leading to mutations in proteins of the respiratory chain, including the subunits of the bc1 complex, result in mitochondrial myopathies, many of which are a direct result of dysfunction at catalytic sites. Some myopathies, especially those in the cytochrome b subunit, exacerbate free-radical damage by enhancing superoxide production at the ubihydroquinone oxidation site. This bypass reaction appears to be an unavoidable feature of the reaction mechanism. Cellular aging is largely attributable to damage to DNA and proteins from the reactive oxygen species arising from superoxide and is a major contributing factor in many diseases of old age. An understanding of the mechanism of the bc1 complex is therefore central to our understanding of the aging process. In addition, a wide range of inhibitors that mimic the quinone substrates are finding important applications in clinical therapy and agronomy. Recent structural studies have shown how many of these inhibitors bind, and have provided important clues to the mechanism of action and the basis of resistance through mutation. This paper reviews recent advances in our understanding of the mechanism of the bc1 complex and their relation to these physiologically important issues in the context of the structural information available.
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Affiliation(s)
- Antony R Crofts
- Department of Biochemistry, and Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
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39
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Finazzi G, Forti G. Metabolic Flexibility of the Green Alga Chlamydomonas reinhardtii as Revealed by the Link between State Transitions and Cyclic Electron Flow. PHOTOSYNTHESIS RESEARCH 2004; 82:327-38. [PMID: 16143844 DOI: 10.1007/s11120-004-0359-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
In this Review we focus on the conversion of linear photosynthetic electron transport from water to NADP to the cyclic pathway around Photosystem I in the green alga Chlamydomonas reinhardtii. We discuss the strict relationship that exists between the changes in pathways of electron transport and state transitions, i.e., the reversible functional association of light harvesting proteins with one of the two photosystems of oxygenic photosynthesis. Such a link has not been reported in the case of other photosynthetic organisms, where the state transitions do not affect the pathway of electron transport. Rather, they provide a tool to optimise the rate of linear flow. We propose a kinetic-structural model that explains the mechanism of this particular relationship in Chlamydomonas, and discuss the advantages that this peculiar situation gives to the energetic metabolism of this alga.
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Affiliation(s)
- Giovanni Finazzi
- Institut de Biologie Physico Chimique, UPR-CNRS 1261 (associée Université Paris 6), 13 rue Pierre et Marie Curie, 75005, Paris, France
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40
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Ben-Shem A, Frolow F, Nelson N. Crystal structure of plant photosystem I. Nature 2003; 426:630-5. [PMID: 14668855 DOI: 10.1038/nature02200] [Citation(s) in RCA: 521] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2003] [Accepted: 10/28/2003] [Indexed: 11/09/2022]
Abstract
Oxygenic photosynthesis is the principal producer of both oxygen and organic matter on Earth. The conversion of sunlight into chemical energy is driven by two multisubunit membrane protein complexes named photosystem I and II. We determined the crystal structure of the complete photosystem I (PSI) from a higher plant (Pisum sativum var. alaska) to 4.4 A resolution. Its intricate structure shows 12 core subunits, 4 different light-harvesting membrane proteins (LHCI) assembled in a half-moon shape on one side of the core, 45 transmembrane helices, 167 chlorophylls, 3 Fe-S clusters and 2 phylloquinones. About 20 chlorophylls are positioned in strategic locations in the cleft between LHCI and the core. This structure provides a framework for exploration not only of energy and electron transfer but also of the evolutionary forces that shaped the photosynthetic apparatus of terrestrial plants after the divergence of chloroplasts from marine cyanobacteria one billion years ago.
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Affiliation(s)
- Adam Ben-Shem
- Department of Biochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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41
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Kurisu G, Zhang H, Smith JL, Cramer WA. Structure of the cytochrome b6f complex of oxygenic photosynthesis: tuning the cavity. Science 2003; 302:1009-14. [PMID: 14526088 DOI: 10.1126/science.1090165] [Citation(s) in RCA: 497] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The cytochrome b6f complex provides the electronic connection between the photosystem I and photosystem II reaction centers of oxygenic photosynthesis and generates a transmembrane electrochemical proton gradient for adenosine triphosphate synthesis. A 3.0 angstrom crystal structure of the dimeric b6f complex from the thermophilic cyanobacterium Mastigocladus laminosus reveals a large quinone exchange cavity, stabilized by lipid, in which plastoquinone, a quinone-analog inhibitor, and a novel heme are bound. The core of the b6f complex is similar to the analogous respiratory cytochrome bc1 complex, but the domain arrangement outside the core and the complement of prosthetic groups are strikingly different. The motion of the Rieske iron-sulfur protein extrinsic domain, essential for electron transfer, must also be different in the b6f complex.
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Affiliation(s)
- Genji Kurisu
- Department of Biological Sciences, 915 West State Street, Purdue University, West Lafayette, IN 47907-2054, USA
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42
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Makino A, Sakuma H, Sudo E, Mae T. Differences between maize and rice in N-use efficiency for photosynthesis and protein allocation. PLANT & CELL PHYSIOLOGY 2003; 44:952-6. [PMID: 14519777 DOI: 10.1093/pcp/pcg113] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The N-use efficiency for photosynthesis was higher in a C(4) plant, maize, than in a C(3) plant, rice, including rbcS antisense rice with optimal ribulose-1,5-bisphosphate carboxylase (Rubisco) content for CO(2)-saturated photosynthesis, even when photosynthesis was measured under saturating CO(2) conditions. The N cost for the C(4) cycle enzymes in maize was not large, and the lower amount of Rubisco allowed a greater N investment in the thylakoid components. This greater content of the thylakoid components as well as the CO(2) concentrating mechanism may support higher N-use efficiency for photosynthesis in maize.
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Affiliation(s)
- Amane Makino
- Department of Applied Plant Science, Graduate School of Agricultural Sciences, Tohoku University, Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, 981-8555 Japan.
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Gross EL, Pearson DC. Brownian dynamics simulations of the interaction of Chlamydomonas cytochrome f with plastocyanin and cytochrome c6. Biophys J 2003; 85:2055-68. [PMID: 12944318 PMCID: PMC1303377 DOI: 10.1016/s0006-3495(03)74633-5] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2002] [Accepted: 05/05/2003] [Indexed: 11/30/2022] Open
Abstract
The interaction of Chlamydomonas cytochrome f (cyt f) with either Chlamydomonas plastocyanin (PC) or Chlamydomonas cytochrome c(6) (cyt c(6)) was studied using Brownian dynamics simulations. The two electron acceptors (PC and cyt c(6)) were found to be essentially interchangeable despite a lack of sequence homology and different secondary structures (beta-sheet for PC and alpha-helix for cyt c(6)). Simulations using PC and cyt c(6) interacting with cyt f showed approximately equal numbers of successful complexes and calculated rates of electron transfer. Cyt f-PC and cyt f-cyt c(6) showed the same types of interactions. Hydrophobic residues surrounding the Y1 ligand to the heme on cyt f interacted with hydrophobic residues on PC (surrounding the H87 ligand to the Cu) or cyt c(6) (surrounding the heme). Both types of complexes were stabilized by electrostatic interactions between K65, K188, and K189 on cyt f and conserved anionic residues on PC (E43, D44, D53, and E85) or cyt c(6) (E2, E70, and E71). Mutations on cyt f had identical effects on its interaction with either PC or cyt c(6). K65A, K188A, and K189A showed the largest effects whereas residues such as K217A, R88A, and K110A, which are located far from the positive patch on cyt f, showed very little inhibition. The effect of mutations observed in Brownian dynamics simulations paralleled those observed in experiments.
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Affiliation(s)
- Elizabeth L Gross
- Department of Biochemistry and Biophysics Program, The Ohio State University, Columbus, Ohio 43210, USA.
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44
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Santillán Torres JL, Atteia A, Claros MG, González-Halphen D. Cytochrome f and subunit IV, two essential components of the photosynthetic bf complex typically encoded in the chloroplast genome, are nucleus-encoded in Euglena gracilis. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1604:180-9. [PMID: 12837550 DOI: 10.1016/s0005-2728(03)00058-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The photosynthetic protist Euglena gracilis contains chloroplasts surrounded by three membranes which arise from secondary endosymbiosis. The genes petA and petD, encoding cytochrome f and subunit IV of the cytochrome bf complex, normally present in chloroplast genomes, are lacking from the chloroplast DNA (cpDNA) of E. gracilis. The bf complex of E. gracilis was isolated, and the identities of cytochrome f and subunit IV were established immunochemically, by heme-specific staining, and by Edman degradation. Based on N-terminal and conserved internal protein sequences, primers were designed and used for PCR gene amplification and cDNA sequencing. The complete sequence of the petA cDNA and the partial sequence of the petD cDNA from E. gracilis are described. Evidence is provided that in this protist, the petA and petD genes have migrated from the chloroplast to the nucleus. Both genes exhibit a typical nuclear codon usage, clearly distinct from the usage of chloroplast genes. The petA gene encodes an atypical cytochrome f, with a unique insertion of 62 residues not present in other f-type cytochromes. The petA gene also acquired a region that encodes a large tripartite chloroplast transit peptide (CTP), which is thought to allow the import of apocytochrome f through the three-membrane envelope of E. gracilis chloroplasts. This is the first description of petA and petD genes that are nucleus-localized.
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Affiliation(s)
- José Luis Santillán Torres
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-243, 04510 Mexico City, Mexico
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Zhang H, Kurisu G, Smith JL, Cramer WA. A defined protein-detergent-lipid complex for crystallization of integral membrane proteins: The cytochrome b6f complex of oxygenic photosynthesis. Proc Natl Acad Sci U S A 2003; 100:5160-3. [PMID: 12702760 PMCID: PMC154315 DOI: 10.1073/pnas.0931431100] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2002] [Accepted: 03/12/2003] [Indexed: 11/18/2022] Open
Abstract
The paucity of integral membrane protein structures creates a major bioinformatics gap, whose origin is the difficulty of crystallizing these detergent-solubilized proteins. The problem is particularly formidable for hetero-oligomeric integral membrane proteins, where crystallization is impeded by the heterogeneity and instability of the protein subunits and the small lateral pressure imposed by the detergent micelle envelope that surrounds the hydrophobic domain. In studies of the hetero (eight subunit)-dimeric 220,000 molecular weight cytochrome b(6)f complex, derived from the thermophilic cyanobacterium, Mastigocladus laminosus, crystals of the complex in an intact state could not be obtained from highly purified delipidated complex despite exhaustive screening. Crystals of proteolyzed complex could be obtained that grew very slowly and diffracted poorly. Addition to the purified lipid-depleted complex of a small amount of synthetic nonnative lipid, dioleolyl-phosphatidylcholine, resulted in a dramatic improvement in crystallization efficiency. Large crystals of the intact complex grew overnight, whose diffraction parameters are as follows: 94% complete at 3.40 A spacing; R(merge) = 8.8% (38.5%), space group, P6(1)22; and unit cell parameters, a = b = 156.3 A, c = 364.0 A, alpha = beta = 90 degrees, gamma = 120 degrees. It is proposed that the methodology of augmentation of a well-defined lipid-depleted integral membrane protein complex with synthetic nonnative lipid, which can provide conformational stability to the protein complex, may be of general use in the crystallization of integral membrane proteins.
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Affiliation(s)
- Huamin Zhang
- Department of Biological Sciences, Lilly Hall of Life Sciences, Purdue University, West Lafayette, IN 47907-2054, USA
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Darrouzet E, Daldal F. Protein-protein interactions between cytochrome b and the Fe-S protein subunits during QH2 oxidation and large-scale domain movement in the bc1 complex. Biochemistry 2003; 42:1499-507. [PMID: 12578362 DOI: 10.1021/bi026656h] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The ubihydroquinone:cytochrome (cyt) c oxidoreductase, or bc(1) complex, and its homologue the b(6)f complex are key components of respiratory and photosynthetic electron transport chains as they contribute to the generation of an electrochemical gradient used by the ATP synthase to produce ATP. The bc(1) complex has two catalytic domains, ubihydroquinone oxidation (Q(o)) and ubiquinone reduction (Q(i)) sites, that are located on each side of the membrane. The key to the energetic efficiency of this enzyme relies upon the occurrence of a unique electron bifurcation reaction at its Q(o) site. Recently, several lines of evidence have converged to establish that in the bc(1) complex the extrinsic domain of the Fe-S subunit that contains a [2Fe2S] metal cluster moves during catalysis to shuttle electrons between the Q(o) site and c(1) heme. While this step is required for electron bifurcation, available data also suggest that the movement might be controlled to ensure maximal energetic efficiency [Darrouzet et al. (2000) Proc. Natl. Acad. Sci. U.S.A. 97, 4567-4572]. To gain insight into the plausible control mechanism, we used a biochemical genetic approach to define the different regions of the bc(1) complex that might interact with each other. Previously, we found that a mutation located at position L286 of the ef loop of Rhodobacter capsulatus cyt b could alleviate movement impairment resulting from a mutation in the hinge region, linking the [2Fe2S] cluster domain to the membrane anchor of the Fe-S subunit. Here we report that various substitutions at position 288 on the opposite side of the ef loop also impair Q(o) site catalysis. In particular, we note that while most of the substitutions affect only QH(2) oxidation, yet others like T288S also hinder the rate of the movement of the Fe-S subunit. Thus, position 288 of cyt b appears to be important for both the QH(2) oxidation and the movement of the Fe-S subunit. Moreover, we found that, upon substitution of T288 by other amino acids, additional compensatory mutations located at the [2Fe2S] cluster or the hinge domains of the Fe-S subunit, or on the cd loop of cyt b, arise readily to alleviate these defects. These studies indicate that intimate protein-protein interactions occur between cyt b and the Fe-S subunits to sustain fast movement and efficient QH(2) oxidation and highlight the critical dual role the ef loop of cyt b to fine-tune the docking and movement of the Fe-S subunit during Q(o) site catalysis.
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Affiliation(s)
- Elisabeth Darrouzet
- Department of Biology, Plant Science Institute, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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Pierre Y, Chabaud E, Hervé P, Zito F, Popot JL. Site-directed photochemical coupling of cytochrome b6f-associated chlorophyll. Biochemistry 2003; 42:1031-41. [PMID: 12549924 DOI: 10.1021/bi026934c] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cytochrome b(6)f complexes contain a molecule of chlorophyll a (Chla), which, in Chlamydomonas reinhardtii, can be exchanged for extraneous chlorophyll during protracted incubation of the purified complex in detergent solution. The specificity of the site and its location in the complex have been studied by photochemical coupling and circular dichroism spectroscopy. Following substitution of the original chlorophyll with [(3)H]Chla, the complex was irradiated in the Soret absorption band of Chla to complete bleaching and the amount of radioactivity covalently bound to each b(6)f subunit determined. Strong labeling was found to be associated with cytochrome f. The labeling originates from [(3)H]Chla molecules bound to a slowly exchanging site and showing the properties of the endogenous Chl, not from molecules dissolved in the detergent belt surrounding the complex. Chlorophyll b (Chlb) can compete with Chla, albeit with a lower affinity. Irradiation of [(3)H]Chlb introduced into the slowly exchanging site yielded the same labeling pattern that was observed with [(3)H]Chla. Proteolytic cleavage showed [(3)H]Chla labeling to be strictly restricted to the C-terminal region of cytochrome f. Circular dichroism spectra of the native complex revealed a bilobed signal characteristic of excitonic interaction between chlorophylls. The structural and evolutionary implications of these findings are discussed.
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Affiliation(s)
- Yves Pierre
- Laboratoire de Physico-Chimie Moléculaire des Membranes Biologiques, UMR 7099, CNRS, and Université Paris-7, Institut de Biologie Physico-Chimique, CNRS IFR 550, 13 rue Pierre et Marie Curie, F-75005 Paris, France
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Li J, Darrouzet E, Dhawan IK, Johnson MK, Osyczka A, Daldal F, Knaff DB. Spectroscopic and oxidation-reduction properties of Rhodobacter capsulatus cytochrome c1 and its M183K and M183H variants. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1556:175-86. [PMID: 12460675 DOI: 10.1016/s0005-2728(02)00360-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Two variants of the cytochrome c1 component of the Rhodobacter capsulatus cytochrome bc1 complex, in which Met183 (an axial heme ligand) was replaced by lysine (M183K) or histidine (M183H), have been analyzed. Electron paramagnetic resonance (EPR) and magnetic circular dichroism (MCD) spectra of the intact complex indicate that the histidine/methionine heme ligation of the wild-type cytochrome is replaced by histidine/lysine ligation in M183K and histidine/histidine ligation in M183H. Variable amounts of histidine/histidine axial heme ligation were also detected in purified wild-type cytochrome c1 and its M183K variant, suggesting that a histidine outside the CSACH heme-binding domain can be recruited as an alternative ligand. Oxidation-reduction titrations of the heme in purified cytochrome c1 revealed multiple redox forms. Titrations of the purified cytochrome carried out in the oxidative or reductive direction differ. In contrast, titrations of cytochrome c1 in the intact bc1 complex and in a subcomplex missing the Rieske iron-sulfur protein were fully reversible. An Em7 value of -330 mV was measured for the single disulfide bond in cytochrome c1. The origins of heme redox heterogeneity, and of the differences between reductive and oxidative heme titrations, are discussed in terms of conformational changes and the role of the disulfide in maintaining the native structure of cytochrome c1.
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Affiliation(s)
- Jun Li
- Department of Chemistry and Biochemistry and Center for Biotechnology and Genomics, Texas Tech University, Box 41061, Lubbock, TX 79409-1061, USA
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Soriano GM, Guo LW, De Vitry C, Kallas T, Cramer WA. Electron transfer from the Rieske iron-sulfur protein (ISP) to cytochrome f in vitro. Is a guided trajectory of the ISP necessary for competent docking? J Biol Chem 2002; 277:41865-71. [PMID: 12207018 DOI: 10.1074/jbc.m205772200] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The time course of electron transfer in vitro between soluble domains of the Rieske iron-sulfur protein (ISP) and cytochrome f subunits of the cytochrome b(6)f complex of oxygenic photosynthesis was measured by stopped-flow mixing. The domains were derived from Chlamydomonas reinhardtii and expressed in Escherichia coli. The expressed 142-residue soluble ISP apoprotein was reconstituted with the [2Fe-2S] cluster. The second-order rate constant, k(2)((ISP-f)) = 1.5 x 10(6) m(-1) s(-1), for ISP to cytochrome f electron transfer was <10(-2) of the rate constant at low ionic strength, k(2)((f-PC))(> 200 x 10(6) m(-1) s(-1)), for the reduction of plastocyanin by cytochrome f, and approximately 1/30 of k(2)((f-PC)) at the ionic strength estimated for the thylakoid interior. In contrast to k(2)((f-PC)), k(2)((ISP-f)) was independent of pH and ionic strength, implying no significant role of electrostatic interactions. Effective pK values of 6.2 and 8.3, respectively, of oxidized and reduced ISP were derived from the pH dependence of the amplitude of cytochrome f reduction. The first-order rate constant, k(1)((ISP-f)), predicted from k(2)((ISP-f)) is approximately 10 and approximately 150 times smaller than the millisecond and microsecond phases of cytochrome f reduction observed in vivo. It is proposed that in the absence of electrostatic guidance, a productive docking geometry for fast electron transfer is imposed by the guided trajectory of the ISP extrinsic domain. The requirement of a specific electrically neutral docking configuration for ISP electron transfer is consistent with structure data for the related cytochrome bc(1) complex.
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Affiliation(s)
- Glenda M Soriano
- Department of Biological Sciences and Program in Biochemistry/Molecular Biology, Purdue University, West Lafayette, Indiana 47907-1392, USA
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Whitelegge JP, Zhang H, Aguilera R, Taylor RM, Cramer WA. Full subunit coverage liquid chromatography electrospray ionization mass spectrometry (LCMS+) of an oligomeric membrane protein: cytochrome b(6)f complex from spinach and the cyanobacterium Mastigocladus laminosus. Mol Cell Proteomics 2002; 1:816-27. [PMID: 12438564 DOI: 10.1074/mcp.m200045-mcp200] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Highly active cytochrome b(6)f complexes from spinach and the cyanobacterium Mastigocladus laminosus have been analyzed by liquid chromatography with electrospray ionization mass spectrometry (LCMS+). Both size-exclusion and reverse-phase separations were used to separate protein subunits allowing measurement of their molecular masses to an accuracy exceeding 0.01% (+/-3 Da at 30,000 Da). The products of petA, petB, petC, petD, petG, petL, petM, and petN were detected in complexes from both spinach and M. laminosus, while the spinach complex also contained ferredoxin-NADP(+) oxidoreductase (Zhang, H., Whitelegge, J. P., and Cramer, W. A. (2001) Flavonucleotide:ferredoxin reductase is a subunit of the plant cytochrome b(6)f complex. J. Biol. Chem. 276, 38159-38165). While the measured masses of PetC and PetD (18935.8 and 17311.8 Da, respectively) from spinach are consistent with the published primary structure, the measured masses of cytochrome f (31934.7 Da, PetA) and cytochrome b (24886.9 Da, PetB) modestly deviate from values calculated based upon genomic sequence and known post-translational modifications. The low molecular weight protein subunits have been sequenced using tandem mass spectrometry (MSMS) without prior cleavage. Sequences derived from the MSMS spectra of these intact membrane proteins in the range of 3.2-4.2 kDa were compared with translations of genomic DNA sequence where available. Products of the spinach chloroplast genome, PetG, PetL, and PetN, all retained their initiating formylmethionine, while the nuclear encoded PetM was cleaved after import from the cytoplasm. While the sequences of PetG and PetN revealed no discrepancy with translations of the spinach chloroplast genome, Phe was detected at position 2 of PetL. The spinach chloroplast genome reports a codon for Ser at position 2 implying the presence of a DNA sequencing error or a previously undiscovered RNA editing event. Clearly, complete annotation of genomic data requires detailed expression measurements of primary structure by mass spectrometry. Full subunit coverage of an oligomeric intrinsic membrane protein complex by LCMS+ presents a new facet to intact mass proteomics.
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Affiliation(s)
- Julian P Whitelegge
- The Pasarow Mass Spectrometry Laboratory, Department of Psychiatry, Neuropsychiatric Institute, University of California, Los Angeles, California 90095, USA.
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