Probing the Electric Field Across Thylakoid Membranes in Cyanobacteria

Total Page:16

File Type:pdf, Size:1020Kb

Probing the Electric Field Across Thylakoid Membranes in Cyanobacteria Probing the electric field across thylakoid membranes in cyanobacteria Stefania Violaa,b, Benjamin Bailleula, Jianfeng Yub, Peter Nixonb, Julien Sellésa, Pierre Joliota, and Francis-André Wollmana,1 aLaboratoire de Biologie du chloroplaste et perception de la lumière chez les micro-algues-UMR7141, Institut de Biologie Physico-Chimique, CNRS-Sorbonne Université, 75005 Paris, France; and bDepartment of Life Sciences, Imperial College, SW7 2AZ London, United Kingdom Edited by Krishna K. Niyogi, University of California, Berkeley, CA, and approved September 16, 2019 (received for review August 9, 2019) In plants, algae, and some photosynthetic bacteria, the ElectroChromic the photosynthetic activity. Upon illumination, each of the com- Shift (ECS) of photosynthetic pigments, which senses the electric ponents of the photosynthetic chain participates in either the for- field across photosynthetic membranes, is widely used to quantify mation (PSII, cytochrome b6f,PSI)orthedissipation(ATP the activity of the photosynthetic chain. In cyanobacteria, ECS synthase) of a proton motive force, which has an electric and an signals have never been used for physiological studies, although osmotic component. Light-induced ECS signals can thus be used to they can provide a unique tool to study the architecture and assess the activities and/or relative amounts of each of the photo- function of the respiratory and photosynthetic electron transfer synthetic complexes (13). ECS measurements can also be used to chains, entangled in the thylakoid membranes. Here, we identified calculate the turnover rates of the photosystems during illumina- bona fide ECS signals, likely corresponding to carotenoid band shifts, tion (14, 15), and to determine the levels of the preexisting elec- in the model cyanobacteria Synechococcus elongatus PCC7942 and trochemical proton gradient in the dark (16, 17). Synechocystis sp. PCC6803. These band shifts, most likely originating In chlorophytes, the electrochromic signals in the 450- to 600-nm from pigments located in photosystem I, have highly similar spectra region of the spectrum are attributed to a combination of ca- in the 2 species and can be best measured as the difference between rotenoid and chlorophyll b band shifts (12, 18). ECS signals the absorption changes at 500 to 505 nm and the ones at 480 to corresponding, in the same spectral region, only to carotenoid 485 nm. These signals respond linearly to the electric field and band shifts have been described in red and brown algae (19), as display the basic kinetic features of ECS as characterized in other well as in microalgae (20) and photosynthetic bacteria (21). In PLANT BIOLOGY organisms. We demonstrate that these probes are an ideal tool to the case of cyanobacteria, earlier studies concluded that the study photosynthetic physiology in vivo, e.g., the fraction of PSI absence of light-induced signals that could be ascribed to ca- centers that are prebound by plastocyanin/cytochrome c6 in dark- rotenoid band shifts (19, 20), in contrast with subsequent reports ness (about 60% in both cyanobacteria, in our experiments), the of putative ECS signals in intact cells (22, 23) and isolated PSI conductivity of the thylakoid membrane (largely reflecting the complexes (24) from different species. Still no ECS-based mea- activity of the ATP synthase), or the steady-state rates of the pho- surements have ever been used for physiological studies. tosynthetic electron transport pathways. Here, we identified bona fide ECS signals in the model cya- nobacteria Synechococcus elongatus PCC7942 and Synechocystis sp. cyanobacteria | photosynthesis | ElectroChromic Shift | electron fluxes PCC6803. We show that these signals are consistent with carot- enoid band shifts, do not originate from PSII, are linearly pro- bout 2.8 billion years ago began the great oxygenation event portional to the light-induced transmembrane electric field, and Acaused by cyanobacteria, the first organisms to perform display all the kinetic properties of ECS. We provide conclusive oxygenic photosynthesis using 2 photosystems linked in series and evidence for a rapid phase in the kinetics of rereduction of P700, water as an electron donor (1, 2). In cyanobacteria, the photo- synthetic and the respiratory electron transfer chains are both lo- Significance cated in the thylakoid membranes, and they share several redox components (3), giving rise to a complex network of electron Cyanobacteria were the first organisms to develop oxygenic fluxes. Moreover, cyanobacteria are proposed to house 2 pathways photosynthesis using water as a source of electrons. Today they for a photosystem II (PSII)-independent electron flow toward remain widespread primary photosynthetic producers and hold a photosystem I (PSI). One is mediated by the NADPH:plastoqui- high biotechnological potential. In cyanobacteria, respiration and none oxidoreductase (NDH) complexes (4, 5), with the other being photosynthesis are interconnected in a complex network of elec- an NDH-independent but ferredoxin-dependent pathway. The tron fluxes. The study of cyanobacterial physiology is hampered molecular nature of the latter requires further elucidation, after by the lack of techniques, allowing a direct measurement of the the characterization of a mutant showing some altered electron transmembrane electric field that develops across their photo- flow (6). No accurate estimation of the physiological turnover rates synthetic/respiratory membranes. Here, we characterized a probe of these pathways is available so far. of the transmembrane electric field, based on the ElectroChromic The study of cyanobacterial photosynthetic fluxes is further Shifts of carotenoids, thus opening unprecedented avenues to complicated by the fact that current methods such as PSII fluo- bioenergetics studies of these major photosynthetic organisms. rescence (7) and PSI absorption spectroscopy (8) measure distinct variables that cannot be quantitatively compared without potential Author contributions: S.V., B.B., P.N., J.S., P.J., and F.-A.W. designed research; S.V., B.B., biases. Moreover, the quantitative interpretation of fluorescence J.Y., J.S., and P.J. performed research; S.V., B.B., J.S., and P.J. analyzed data; and S.V., B.B., parameters in cyanobacteria is hampered by a number of pitfalls (9, J.S., P.J., and F.-A.W. wrote the paper. 10). A powerful tool to measure photosynthetic activity, extensively The authors declare no competing interest. used in plants, algae, and several photosynthetic bacteria, is the This article is a PNAS Direct Submission. ElectroChromic Shift (ECS) of photosynthetic pigments (11, 12), Published under the PNAS license. which is based on a physical phenomenon known as the Stark ef- 1To whom correspondence may be addressed. Email: [email protected]. fect. This method relies on the shift of the absorption spectrum of This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. some photosynthetic pigments in the thylakoid membrane in re- 1073/pnas.1913099116/-/DCSupplemental. sponse to changes in the transmembrane electric field generated by www.pnas.org/cgi/doi/10.1073/pnas.1913099116 PNAS Latest Articles | 1of7 Downloaded by guest on September 28, 2021 the special pair of PSI, in vivo in both cyanobacteria. We also measured after 100 ms are pure ECS spectra, which present demonstrate that the identified electrochromic probes can be minima at 430, 455, 485, and 560 nm; maxima at 450, 470, and used to study the changes in membrane permeability and the 500 nm; and a broad positive region at 510 to 540 nm. We also electron flow rates. note that the addition of PMS caused a progressive decrease in the ECS amplitude in the green region of the spectrum (510 to 540 Results and Discussion nm) in S. elongatus. This is caused by the appearance of a negative Flash-Induced Carotenoid Band Shifts in S. elongatus and Synechocystis. signal peaking around 515 nm that superimposed itself to ECS We recorded the spectra of the absorption changes induced by during the time course of the experiment (about 2 h between the single-turnover saturating flashes in S. elongatus. Cells were placed forth and the back recordings in anaerobic conditions). As shown in anaerobic conditions in the presence of the PSII inhibitors 3- in SI Appendix,Fig.S4A and B and further discussed in the SI (3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and hydrox- Appendix, the progressive bleaching was present also when re- ylamine (HA), to eliminate the absorption changes produced by cording spectra in the absence of PMS, although to a much lesser PSII turnovers. We recorded these spectra 19 ms after the flash, extent. We do not have direct evidence of the nature of such a followed by 5 detecting flashes given 100 ms apart, to minimize the signal, although the spectrum of the difference between the forth contribution of redox-dependent absorption changes that mostly and the back recordings may also be due to a change in the band relax before 19 ms (SI Appendix,Fig.S2). As shown in Fig. 1A,the shift of a carotenoid. These spectral changes did not affect the decay of the absorption changes was uniform in the 450- to 550-nm amplitudes of the negative peak at 480 to 485 nm and the positive region: all spectra show 2 minima peaking around 455 and 485 nm; peak at 500 to 505 nm. 3 maxima at 450, 470, and 500 nm; and a broad featureless positive We investigated the presence of ECS in another commonly region between 510 and 540 nm. On the edges of the recorded used cyanobacterium, Synechocystis sp. PCC6803. Fig. 1C and SI spectral region was a transient bleaching at 420 to 425 nm and Appendix,Fig.S3C show the spectra of flash-induced absorption 554 nm that we attribute to the oxidation of the c-type haem of changes recorded in presence of 15 μMPMSinDCMUandHA- cytochrome f (and possibly of cyt c6), and an absorbance increase treated cells. The spectra showed a predominant component with at 435 nm and 560 nm, which we attribute to the reduction of the homothetic decay and a shape highly similar to the electrochromic bH haem of cyt b (25).
Recommended publications
  • Light-Induced Psba Translation in Plants Is Triggered by Photosystem II Damage Via an Assembly-Linked Autoregulatory Circuit
    Light-induced psbA translation in plants is triggered by photosystem II damage via an assembly-linked autoregulatory circuit Prakitchai Chotewutmontria and Alice Barkana,1 aInstitute of Molecular Biology, University of Oregon, Eugene, OR 97403 Edited by Krishna K. Niyogi, University of California, Berkeley, CA, and approved July 22, 2020 (received for review April 26, 2020) The D1 reaction center protein of photosystem II (PSII) is subject to mRNA to provide D1 for PSII repair remain obscure (13, 14). light-induced damage. Degradation of damaged D1 and its re- The consensus view in recent years has been that psbA transla- placement by nascent D1 are at the heart of a PSII repair cycle, tion for PSII repair is regulated at the elongation step (7, 15–17), without which photosynthesis is inhibited. In mature plant chloro- a view that arises primarily from experiments with the green alga plasts, light stimulates the recruitment of ribosomes specifically to Chlamydomonas reinhardtii (Chlamydomonas) (18). However, we psbA mRNA to provide nascent D1 for PSII repair and also triggers showed recently that regulated translation initiation makes a a global increase in translation elongation rate. The light-induced large contribution in plants (19). These experiments used ribo- signals that initiate these responses are unclear. We present action some profiling (ribo-seq) to monitor ribosome occupancy on spectrum and genetic data indicating that the light-induced re- cruitment of ribosomes to psbA mRNA is triggered by D1 photo- chloroplast open reading frames (ORFs) in maize and Arabi- damage, whereas the global stimulation of translation elongation dopsis upon shifting seedlings harboring mature chloroplasts is triggered by photosynthetic electron transport.
    [Show full text]
  • 4.3 the Light-Dependent 4B, 9B Photosynthesis Indetail 9B Transfers Energy
    DO NOT EDIT--Changes must be made through “File info” CorrectionKey=B 4.3 Photosynthesis in Detail 4B, 9B KEY CONCEPT Photosynthesis requires a series of chemical reactions. VOCABULARY MAIN IDEAS photosystem The first stage of photosynthesis captures and transfers energy. electron transport chain The second stage of photosynthesis uses energy from the first stage to make sugars. ATP synthase Calvin cycle Connect to Your World In a way, the sugar-producing cells in leaves are like tiny factories with assembly lines. 4B investigate and explain cellular processes, including In a factory, different workers with separate jobs have to work together to put homeostasis, energy conversions, together a finished product. Similarly, in photosynthesis many different chemical transport of molecules, and synthesis of new molecules and 9B reactions, enzymes, and ions work together in a precise order to make the sugars compare the reactants and products that are the finished product. of photosynthesis and cellular respiration in terms of energy and matter MaiN IDEA 4B, 9B The first stage of photosynthesis captures and transfers energy. In Section 2, you read a summary of photosynthesis. However, the process is much more involved than that general description might suggest. For exam- ple, during the light-dependent reactions, light energy is captured and trans- ferred in the thylakoid membranes by two groups of molecules called photosystems. The two photosystems are called photosystem I and photosys- tem II. Overview of the Light-Dependent Reactions FIGURE 3.1 The light-dependent The light-dependent reactions are the photo- part of photosynthesis. During reactions capture energy from sun- light and transfer energy through the light-dependent reactions, chlorophyll and other light-absorbing electrons.
    [Show full text]
  • Chapter 3 the Title and Subtitle of This Chapter Convey a Dual Meaning
    3.1. Introduction Chapter 3 The title and subtitle of this chapter convey a dual meaning. At first reading, the subtitle Photosynthetic Reaction might seem to indicate that the topic of the structure, function and organization of Centers: photosynthetic reaction centers is So little time, so much to do exceedingly complex and that there is simply insufficient time or space in this brief article to cover the details. While this is John H. Golbeck certainly the case, the subtitle is Department of Biochemistry additionally meant to convey the idea that there is precious little time after the and absorption of a photon to accomplish the Molecular Biology task of preserving the energy in the form of The Pennsylvania State University stable charge separation. University Park, PA 16802 USA The difficulty is there exists a fundamental physical limitation in the amount of time available so that a photochemically induced excited state can be utilized before the energy is invariably wasted. Indeed, the entire design philosophy of biological reaction centers is centered on overcoming this physical, rather than chemical or biological, limitation. In this chapter, I will outline the problem of conserving the free energy of light-induced charge separation by focusing on the following topics: 3.2. Definition of the problem: the need to stabilize a charge-separated state. 3.3. The bacterial reaction center: how the cofactors and proteins cope with this problem in a model system. 3.4. Review of Marcus theory: what governs the rate of electron transfer in proteins? 3.5. Photosystem II: a variation on a theme of the bacterial reaction center.
    [Show full text]
  • Lecture Inhibition of Photosynthesis Inhibition at Photosystem I
    1 Lecture Inhibition of Photosynthesis Inhibition at Photosystem I 1. General Information The popular misconception is that susceptible plants treated with these herbicides “starve to death” because they can no longer photosynthesize. In actuality, the plants die long before the food reserves are depleted. The photosynthetic inhibitors can be divided into two distinct groups, the inhibitors of Photosystem I and inhibitors of Photosystem II. Both of these groups work in the energy production step of photosynthesis, or the light reactions. Light is required as well as photosynthesis for these herbicides to kill susceptible plants. Herbicides that inhibit Photosystem I are considered to be contact herbicides and are often referred to as membrane disruptors. The end result is that cell membranes are rapidly destroyed resulting in leakage of cell contents into the intercellular spaces. These herbicides act as “electron interceptors” or “electron thieves” within Photosystem I of the light reaction of photosynthesis. They divert electrons from the normal electron transport sequence necessary in Photosystem I. This in turn inhibits photosynthesis. The membrane disruption occurs as a result of secondary responses. Herbicides that inhibit Photosystem I are represented by only one family, the bipyridyliums. See chemical structure shown under herbicide families. These molecules are cationic (positively charged) and are therefore highly water soluble. Their cationic properties also make them highly adsorbed to soil colloids resulting in no soil activity. 2. Mode of Action See Figure 7.1 (The electron transport chain in photosynthesis and the sites of action of herbicides that interfere with electron transfer in this chain (Q = electron acceptor; PQ = plastoquinone).
    [Show full text]
  • Photosystem I-Based Applications for the Photo-Catalyzed Production of Hydrogen and Electricity
    University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 12-2014 Photosystem I-Based Applications for the Photo-catalyzed Production of Hydrogen and Electricity Rosemary Khuu Le University of Tennessee - Knoxville, [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Part of the Biochemical and Biomolecular Engineering Commons Recommended Citation Le, Rosemary Khuu, "Photosystem I-Based Applications for the Photo-catalyzed Production of Hydrogen and Electricity. " PhD diss., University of Tennessee, 2014. https://trace.tennessee.edu/utk_graddiss/3146 This Dissertation is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a dissertation written by Rosemary Khuu Le entitled "Photosystem I- Based Applications for the Photo-catalyzed Production of Hydrogen and Electricity." I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Doctor of Philosophy, with a major in Chemical Engineering. Paul D. Frymier, Major Professor We have read this dissertation and recommend its acceptance: Eric T. Boder, Barry D. Bruce, Hugh M. O'Neill Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) Photosystem I-Based Applications for the Photo-catalyzed Production of Hydrogen and Electricity A Dissertation Presented for the Doctor of Philosophy Degree The University of Tennessee, Knoxville Rosemary Khuu Le December 2014 Copyright © 2014 by Rosemary Khuu Le All rights reserved.
    [Show full text]
  • Can Ferredoxin and Ferredoxin NADP(H) Oxidoreductase Determine the Fate of Photosynthetic Electrons?
    Send Orders for Reprints to [email protected] Current Protein and Peptide Science, 2014, 15, 385-393 385 The End of the Line: Can Ferredoxin and Ferredoxin NADP(H) Oxidoreductase Determine the Fate of Photosynthetic Electrons? Tatjana Goss and Guy Hanke* Department of Plant Physiology, Faculty of Biology and Chemistry, University of Osnabrück,11 Barbara Strasse, Osnabrueck, DE-49076, Germany Abstract: At the end of the linear photosynthetic electron transfer (PET) chain, the small soluble protein ferredoxin (Fd) transfers electrons to Fd:NADP(H) oxidoreductase (FNR), which can then reduce NADP+ to support C assimilation. In addition to this linear electron flow (LEF), Fd is also thought to mediate electron flow back to the membrane complexes by different cyclic electron flow (CEF) pathways: either antimycin A sensitive, NAD(P)H complex dependent, or through FNR located at the cytochrome b6f complex. Both Fd and FNR are present in higher plant genomes as multiple gene cop- ies, and it is now known that specific Fd iso-proteins can promote CEF. In addition, FNR iso-proteins vary in their ability to dynamically interact with thylakoid membrane complexes, and it has been suggested that this may also play a role in CEF. We will highlight work on the different Fd-isoproteins and FNR-membrane association found in the bundle sheath (BSC) and mesophyll (MC) cell chloroplasts of the C4 plant maize. These two cell types perform predominantly CEF and LEF, and the properties and activities of Fd and FNR in the BSC and MC are therefore specialized for CEF and LEF re- spectively.
    [Show full text]
  • (CP) Gene of Papaya Ri
    Results and Discussion 4. RESULTS AND DISCUSSION 4.1 Genetic diversity analysis of coat protein (CP) gene of Papaya ringspot virus-P (PRSV-P) isolates from multiple locations of Western India Results – 4.1.1 Sequence analysis In this study, fourteen CP gene sequences of PRSV-P originating from multiple locations of Western Indian States, Gujarat and Maharashtra (Fig. 3.1), have been analyzed and compared with 46 other CP sequences from different geographic locations of America (8), Australia (1), Asia (13) and India (24) (Table 4.1; Fig. 4.1). The CP length of the present isolates varies from 855 to 861 nucleotides encoding 285 to 287 amino acids. Fig. 4.1: Amplification of PRSV-P coat protein (CP) gene from 14 isolates of Western India. From left to right lanes:1: Ladder (1Kb), 2: IN-GU-JN, 3: IN-GU-SU, 4: IN-GU-DS, 5: IN-GU-RM, 6: IN-GU-VL, 7: IN-MH-PN, 8: IN-MH-KO, 9: IN-MH-PL, 10: IN-MH-SN, 11: IN-MH-JL, 12: IN-MH-AM, 13: IN-MH-AM, 14: IN-MH-AK, 15: IN-MH-NS,16: Negative control. Red arrow indicates amplicon of Coat protein (CP) gene. Table 4.1: Sources of coat protein (CP) gene sequences of PRSV-P isolates from India and other countries used in this study. Country Name of Length GenBank Origin¥ Reference isolates* (nts) Acc No IN-GU-JN GU-Jamnagar 861 MG977140 This study IN-GU-SU GU-Surat 855 MG977142 This study IN-GU-DS GU-Desalpur 855 MG977139 This study India IN-GU-RM GU-Ratlam 858 MG977141 This study IN-GU-VL GU-Valsad 855 MG977143 This study IN-MH-PU MH-Pune 861 MH311882 This study Page | 36 Results and Discussion IN-MH-PN MH-Pune
    [Show full text]
  • Thylakoid Membrane Architecture in Cyanobacteria
    THYLAKOID MEMBRANE ARCHITECTURE IN CYANOBACTERIA Dissertation zur Erlangung des Grades eines Doktors der Naturwissenschaften an der Fakultät für Biologie der Ludwig-Maximilians-Universität München vorgelegt von Anna Margareta Rast München, 03. Mai 2018 1. Gutachter: Prof. Dr. Jörg Nickelsen 2. Gutachter: Prof. Dr. Andreas Klingl Tag der Abgabe: 03.05.2018 Tag der mündlichen Prüfung: 22.06.2018 2 TABLE OF CONTENT TABLE OF CONTENT SUMMARY 5 ZUSAMMENFASSUNG 7 1 INTRODUCTION 9 1.1 Evolution of oxygenic photosynthesis 9 1.2 Thylakoid structure 10 1.2.1 Thylakoid structure in plastids 10 1.2.2 Thylakoid structure in cyanobacteria 11 1.3 Thylakoid membrane shaping factors 13 1.4 Photosynthesis in cyanobacteria 17 1.4.1 Electron transport chain 17 1.4.2 Light harvesting 19 1.4.3 Lateral heterogeneity 20 1.5 PSII biogenesis and repair in cyanobacteria 21 1.6 Cryo-electron tomography 23 2 AIMS OF THIS WORK 27 3 RESULTS 28 3.1 The role of Slr0151, a tetratricopeptide repeat protein from Synechocystis sp. PCC 6803, during photosystem II assembly and repair 28 3.2 Thylakoid membrane architecture in Synechocystis depends on CurT, a homolog of the granal CURVATURE THYLAKOID1 proteins 41 3.3 In situ cryo-electron tomography of cyanobacterial thylakoid convergence zones reveals a biogenic membrane connecting thylakoids to the plasma membrane. 65 4 DISCUSSION 86 4.1 Structural and photosystem II specific role of Slr0151 and CurT 86 4.1.1 The role of Slr0151 86 4.1.2 The role of CurT 88 4.1.3 Connection between Slr0151 and CurT via phosphorylation? 90 4.2 The thylapse – a contact area between thylakoids and plasma membrane 91 4.2.1 Factors possibly involved in thylapse formation 93 4.2.2 Membrane contact – a common feature 94 4.3 Lateral heterogeneity in cyanobacteria 95 4.4 Conclusions and future perspectives 97 3 TABLE OF CONTENT 5 REFERENCES 99 6 APPENDIX 112 6.1 Biogenesis of thylakoid membranes 112 6.2 Supplementary Material - The role of Slr0151, a tetratricopeptide repeat protein from Synechocystis sp.
    [Show full text]
  • Glycolysis Citric Acid Cycle Oxidative Phosphorylation Calvin Cycle Light
    Stage 3: RuBP regeneration Glycolysis Ribulose 5- Light-Dependent Reaction (Cytosol) phosphate 3 ATP + C6H12O6 + 2 NAD + 2 ADP + 2 Pi 3 ADP + 3 Pi + + 1 GA3P 6 NADP + H Pi NADPH + ADP + Pi ATP 2 C3H4O3 + 2 NADH + 2 H + 2 ATP + 2 H2O 3 CO2 Stage 1: ATP investment ½ glucose + + Glucose 2 H2O 4H + O2 2H Ferredoxin ATP Glyceraldehyde 3- Ribulose 1,5- Light Light Fx iron-sulfur Sakai-Kawada, F Hexokinase phosphate bisphosphate - 4e + center 2016 ADP Calvin Cycle 2H Stroma Mn-Ca cluster + 6 NADP + Light-Independent Reaction Phylloquinone Glucose 6-phosphate + 6 H + 6 Pi Thylakoid Tyr (Stroma) z Fe-S Cyt f Stage 1: carbon membrane Phosphoglucose 6 NADPH P680 P680* PQH fixation 2 Plastocyanin P700 P700* D-(+)-Glucose isomerase Cyt b6 1,3- Pheophytin PQA PQB Fructose 6-phosphate Bisphosphoglycerate ATP Lumen Phosphofructokinase-1 3-Phosphoglycerate ADP Photosystem II P680 2H+ Photosystem I P700 Stage 2: 3-PGA Photosynthesis Fructose 1,6-bisphosphate reduction 2H+ 6 ADP 6 ATP 6 CO2 + 6 H2O C6H12O6 + 6 O2 H+ + 6 Pi Cytochrome b6f Aldolase Plastoquinol-plastocyanin ATP synthase NADH reductase Triose phosphate + + + CO2 + H NAD + CoA-SH isomerase α-Ketoglutarate + Stage 2: 6-carbonTwo 3- NAD+ NADH + H + CO2 Glyceraldehyde 3-phosphate Dihydroxyacetone phosphate carbons Isocitrate α-Ketoglutarate dehydogenase dehydrogenase Glyceraldehyde + Pi + NAD Isocitrate complex 3-phosphate Succinyl CoA Oxidative Phosphorylation dehydrogenase NADH + H+ Electron Transport Chain GDP + Pi 1,3-Bisphosphoglycerate H+ Succinyl CoA GTP + CoA-SH Aconitase synthetase
    [Show full text]
  • Structure of the Cytochrome B6 F Complex of Oxygenic Photosynthesis
    Structure of the Cytochrome b6 f Complex of Oxygenic Photosynthesis The photosynthetic unit of oxygenic photosynthesis data of 3.0 Å from the complex crystal with another is organized as two large multimolecular membrane analogue inhibitor, TDS, was collected at the SBC complexes, photosystem II (PSII) that extracts low- beamline 19ID, APS. The initial model was developed energy electrons from water and photosystem I (PSI) into a 3.4 Å map of the native complex. Final that raises the energy level of such electrons using refinement was carried out with a dataset from a co- light energy to produce a strong reductant, NADPH. crystal with TDS (Figs. 2, 3). The two photosystems operate in a series linked by a Viewed along the membrane normal, the b6f × third multiprotein complex called the cytochrome b6f complex is 90 Å 55 Å within the membrane side, × complex (Fig.1). The cytochrome b6f complex is a and 120 Å 75 Å on the lumen (p)side (Fig. 2). A membrane-spanning protein complex embedded in prominent feature of this structure is an extended the thylakoid membrane of photosynthetic organisms. quinone exchange cavity between the monomers, The molecular weight of the complex is 220,000 as a which exchanges lipophilic plastoquinone in the dimer with 26 transmembrane helices. The b6f complex bilayer center, and also mediates the electron and controls the electron transfer between the plastoquinol proton transfer across the complex. The heme-binding reduced by PSII and the electron carrier protein 4 transmembrane helices core of the b6f complex plastocyanin that associate with PSI.
    [Show full text]
  • Chloroplast Genes Are Expressed During Intracellular Symbiotic
    Proc. Natl. Acad. Sci. USA Vol. 93, pp. 12333-12338, October 1996 Cell Biology Chloroplast genes are expressed during intracellular symbiotic association of Vaucheria litorea plastids with the sea slug Elysia chlorotica (photosystem II reaction center/photosynthesis/chromophytic alga/ascoglossan mollusc/gene expression) CESAR V. MUJER*t, DAVID L. ANDREWS*t, JAMES R. MANHART§, SIDNEY K. PIERCES, AND MARY E. RUMPHO*II Departments of *Horticultural Sciences and §Biology, Texas A & M University, College Station, TX 77843; and IDepartment of Zoology, University of Maryland, College Park, MD 20742 Communicated by Martin Gibbs, Brandeis University, Waltham, MA, August 16, 1996 (received for review January 26, 1996) ABSTRACT The marine slug Elysia chlorotica (Gould) lowing metamorphosis from the veliger stage when juvenile forms an intracellular symbiosis with photosynthetically ac- sea slugs begin to feed on V litorea cells (1, 2). Once ingested, tive chloroplasts from the chromophytic alga Vaucheria litorea the chloroplasts are phagocytically incorporated into the cy- (C. Agardh). This symbiotic association was characterized toplasm of one of two morphologically distinct, epithelial cells over a period of 8 months during which E. chlorotica was (3) and maintain their photosynthetic function (1, 3). The deprived of V. litorea but provided with light and CO2. The fine plastids are frequently found in direct contact with the host structure of the symbiotic chloroplasts remained intact in E. cytoplasm as revealed by ultrastructural studies (3). In nature, chlorotica even after 8 months of starvation as revealed by the adult animal feeds on algae only sporadically, obtaining electron microscopy. Southern blot analysis of total DNA metabolic energy from the photosynthetic activity of the from E.
    [Show full text]
  • Chloroplast Is the "Proteinaceous Shield" Regulating Photosystemii Electron Transport and Mediating Diuron Herbicide Sensitivity
    Proc. Nati. Acad. Sci. USA Vol. 78, No. 3, pp. 1572-1576, March 1981 Biochemistry The rapidly metabolized 32,000-dalton polypeptide of the chloroplast is the "proteinaceous shield" regulating photosystem II electron transport and mediating diuron herbicide sensitivity (Spirodela/thylakoids/triazine/photosynthesis) AUTAR K. MATTOO*t, URI PICKO, HEDDA HOFFMAN-FALK*, AND MARVIN EDELMAN* Departments of *Plant Genetics and tBiochemistry, The Weizmann Institute of Science, Rehovot, Israel Communicated by Martin Gibbs, December 5, 1980 ABSTRACT Mild trypsin treatment of Spirodela oligorrhiza plex (LHCP) (14). In Spirodela this rapidly metabolized thy- thylakoid membranes leaks to partial digestion of the rapidly me- lakoid protein is translated by a discrete poly(A)- plastid mes- tabolized, surface-exposed, 32,000-dalton protein. Under these senger RNA of =500 conditions, photoreduction of ferricyanide becomes insensitive to kDal (15) into a 33.5-kDal precursor diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea], an inhibitor of molecule, which is speedily processed into the mature 32-kDal photosystem II electron transport. Preincubation of thylakoids form (13). Differentiated thylakoids are a prerequisite for 33.5- with diuron leads to a conformational change in the 32,000-dalton kDal protein synthesis (16). In addition, the whole process of protein, modifying its trypsin digestion and preventing expression 33.5/32-kDal synthesis, maturation, and degradation is under of diuron insensitivity. Finally, light affects the susceptibility of tight inductive control by light (17, 18). the 32,000-dalton protein to digestion by trypsin. In other exper- The iments, thylakoids specifically depleted in the 32,000-dalton pro- -rapidly metabolized 32-kDal thylakoid protein of Spi- tein were found to be deficient in electron transport at the re- rodela has its counterpart in other higher plants and algae.
    [Show full text]