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  • Apoptosis inducing factor: Cellular protective function in Dictyostelium discoideum
    BBA Bioenerg. (IF 4.441) Pub Date : 2020-01-25
    Ashlesha Kadam; Darshan Mehta; Tina Jubin; Mohmmad Shoab Mansuri; Rasheedunnisa Begum
    更新日期:2020-01-26
  • Embelin averts MPTP-induced dysfunction in mitochondrial bioenergetics and biogenesis via activation of SIRT1
    BBA Bioenerg. (IF 4.441) Pub Date : 2020-01-24
    Swetha Pavani Rao; Neelam Sharma; Shasi V. Kalivendi
    更新日期:2020-01-24
  • Design principles of solar light harvesting in plants: Functional architecture of the monomeric antenna CP29
    BBA Bioenerg. (IF 4.441) Pub Date : 2020-01-24
    Vincenzo Mascoli; Vladimir Novoderezhkin; Nicoletta Liguori; Pengqi Xu; Roberta Croce

    In plants and green algae, light-harvesting complexes (LHCs) are a large family of chlorophyll binding proteins functioning as antennae, collecting solar photons and transferring the absorbed energy to the photosynthetic reaction centers, where light to chemical energy conversion begins. Although LHCs are all highly homologous in their structure and display a variety of common features, each complex finds a specific location and task in the energy transport. One example is CP29, which occupies a pivotal position in Photosystem II, bridging the peripheral antennae to the core. The design principles behind this specificity, however, are still unclear. Here, a synergetic approach combining steady-state and ultrafast spectroscopy, mutational analysis and structure-based exciton modeling allows uncovering the energy landscape of the chlorophylls bound to this complex. We found that, although displaying an overall highly conserved exciton structure very similar to that of other LHCs, CP29 possesses an additional terminal emitter domain. The simultaneous presence of two low energy sites facing the peripheral antennae and the core, allows CP29 to efficiently work as a conduit in the energy flux. Our results show that the LHCs share a common solid architecture but have finely tuned their structure to carry out specific functions.

    更新日期:2020-01-24
  • PGR5 and NDH-1 systems do not function as protective electron acceptors but mitigate the consequences of PSI inhibition
    BBA Bioenerg. (IF 4.441) Pub Date : 2020-01-11
    Sanna Rantala; Tapio Lempiäinen; Caterina Gerotto; Arjun Tiwari; Eva-Mari Aro; Mikko Tikkanen

    Avoidance of photoinhibition at photosystem (PS)I is based on synchronized function of PSII, PSI, Cytochrome b6f and stromal electron acceptors. Here, we used a special light regime, PSI photoinhibition treatment (PIT), in order to specifically inhibit PSI by accumulating excess electrons at the photosystem (Tikkanen and Frebe, 2018). In the analysis, Arabidopsis thaliana WT was compared to the pgr5 and ndho mutants, deficient in one of the two main cyclic electron transfer pathways, described to function as protective alternative electron acceptors of PSI. The aim was to investigate whether the PGR5 (pgr5) and the type I NADH dehydrogenase (NDH-1) (ndho) systems protect PSI from excess electron stress and whether these systems help plants to cope with the consequences of PSI photoinhibition. First, our data reveals that neither PGR5 nor NDH-1 system protects PSI from a sudden burst of electrons. This strongly suggests that these systems in Arabidopsis thaliana do not function as direct acceptors of electrons delivered from PSII to PSI – contrasting with the flavodiiron proteins that were found to make Physcomitrella patens PSI resistant to the PIT. Second, it is demonstrated that under light-limiting conditions, the electron transfer rate at PSII is linearly dependent on the amount of functional PSI in all genotypes, while under excess light, the PGR5-dependent control of electron flow at the Cytochrome b6f complex overrides the effect of PSI inhibition. Finally, the PIT is shown to increase the amount of PGR5 and NDH-1 as well as of PTOX, suggesting that they mitigate further damage to PSI after photoinhibition rather than protect against it.

    更新日期:2020-01-13
  • Binding of red form of Orange Carotenoid Protein (OCP) to phycobilisome is not sufficient for quenching
    BBA Bioenerg. (IF 4.441) Pub Date : 2020-01-11
    Wenjing Lou; Dariusz M. Niedzwiedzki; Ruidong J. Jiang; Robert E. Blankenship; Haijun Liu
    更新日期:2020-01-13
  • Respiratory complex I – Mechanistic insights and advances in structure determination
    BBA Bioenerg. (IF 4.441) Pub Date : 2020-01-11
    Etienne Galemou Yoga; Heike Angerer; Kristian Parey; Volker Zickermann

    Complex I is the largest and most intricate redox-driven proton pump of the respiratory chain. The structure of bacterial and mitochondrial complex I has been determined by X-ray crystallography and cryo-EM at increasing resolution. The recent cryo-EM structures of the complex I-like NDH complex and membrane bound hydrogenase open a new and more comprehensive perspective on the complex I superfamily. Functional studies and molecular modeling approaches have greatly advanced our understanding of the catalytic cycle of complex I. However, the molecular mechanism by which energy is extracted from the redox reaction and utilized to drive proton translocation is unresolved and a matter of ongoing debate. Here, we review progress in structure determination and functional characterization of complex I and discuss current mechanistic models.

    更新日期:2020-01-13
  • Kinetic and structural insight into a role of the re-face Tyr328 residue of the homodimer type ferredoxin-NADP+ oxidoreductase from Rhodopseudomonas palustris in the reaction with NADP+/NADPH
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-12-12
    Daisuke Seo; Norifumi Muraki; Genji Kurisu

    Among the thioredoxin reductase-type ferredoxin-NAD(P)+ oxidoreductase (FNR) family, FNR from photosynthetic purple non‑sulfur bacterium Rhodopseudomonas palustris (RpFNR) is distinctive because the predicted residue on the re-face of the isoalloxazine ring portion of the FAD prosthetic group is a tyrosine. Here, we report the crystal structure of wild type RpFNR and kinetic analyses of the reaction of wild type, and Y328F, Y328H and Y328S mutants with NADP+/NADPH using steady state and pre-steady state kinetic approaches. The obtained crystal structure of wild type RpFNR confirmed the presence of Tyr328 on the re-face of the isoalloxazine ring of the FAD prosthetic group through the unique hydrogen bonding of its hydroxyl group. In the steady state assays, the substitution results in the decrease of Kd for NADP+ and KM for NADPH in the diaphorase assay; however, the kcat values also decreased significantly. In the stopped-flow spectrophotometry, mixing oxidized RpFNRs with NADPH and reduced RpFNRs with NADP+ resulted in rapid charge transfer complex formation followed by hydride transfer. The observed rate constants for the hydride transfer in both directions were comparable (>400 s−1). The substitution did not drastically affect the rate of hydride transfer, but substantially slowed down the subsequent release and re-association of NADP+/NADPH in both directions. The obtained results suggest that Tyr328 stabilizes the stacking of C-terminal residues on the isoalloxazine ring portion of the FAD prosthetic group, which impedes the access of NADP+/NADPH on the isoalloxazine ring portions, in turn, enhancing the release of the NADP+/NADPH and/or reaction with electron transfer proteins.

    更新日期:2019-12-13
  • On the nature of uncoupled chlorophylls in the extremophilic photosystem I-light harvesting I supercomplex
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-12-09
    Sebastian Szewczyk, Mateusz Abram, Rafał Białek, Patrycja Haniewicz, Jerzy Karolczak, Jacek Gapiński, Joanna Kargul, Krzysztof Gibasiewicz

    Photosystem I core-light-harvesting antenna supercomplexes (PSI-LHCI) were isolated from the extremophilic red alga Cyanidioschyzon merolae and studied by three fluorescence techniques in order to characterize chlorophylls (Chls) energetically uncoupled from the PSI reaction center (RC). Such Chls are observed in virtually all optical experiments of any PSI core and PSI-LHCI supercomplex preparations across various species and may influence the operation of PSI-based solar cells and other biohybrid systems. However, the nature of the uncoupled Chls (uChls) has never been explored deeply before. In this work, the amount of uChls was controlled by stirring the solution of C. merolae PSI-LHCI supercomplex samples at elevated temperature (~303 K) and was found to increase from <2% in control samples up to 47% in solutions stirred for 3.5 h. The fluorescence spectrum of uChls was found to be blue-shifted by ~20 nm (to ~680 nm) relative to the fluorescence band from Chls that are well coupled to PSI RC. This effect indicates that mechanical stirring leads to disappearance of some red Chls (emitting at above ~700 nm) that are present in the intact LHCI antenna associated with the PSI core. Comparative diffusion studies of control and stirred samples by fluorescence correlation spectroscopy together with biochemical analysis by SDS-PAGE and BN-PAGE indicate that energetically uncoupled Lhcr subunits are likely to be still physically attached to the PSI core, albeit with altered three-dimensional organization due to the mechanical stress.

    更新日期:2019-12-09
  • Human erythrocytes exposure to juglone leads to an increase of superoxide anion production associated with cytochrome b5 reductase uncoupling
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-12-09
    Gabriel N. Valério, Carlos Gutiérrez-Merino, Fatima Nogueira, Isabel Moura, José J.G. Moura, Alejandro K. Samhan-Arias
    更新日期:2019-12-09
  • Bioenergetic consequences from xenotopic expression of a tunicate AOX in mouse mitochondria: Switch from RET and ROS to FET
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-12-09
    Marten Szibor, Timur Gainutdinov, Erika Fernandez-Vizarra, Eric Dufour, Zemfira Gizatullina, Grazyna Debska-Vielhaber, Juliana Heidler, Ilka Wittig, Carlo Viscomi, Frank Gellerich, Anthony L. Moore

    Electron transfer from all respiratory chain dehydrogenases of the electron transport chain (ETC) converges at the level of the quinone (Q) pool. The Q redox state is thus a function of electron input (reduction) and output (oxidation) and closely reflects the mitochondrial respiratory state. Disruption of electron flux at the level of the cytochrome bc1 complex (cIII) or cytochrome c oxidase (cIV) shifts the Q redox poise to a more reduced state which is generally sensed as respiratory stress. To cope with respiratory stress, many species, but not insects and vertebrates, express alternative oxidase (AOX) which acts as an electron sink for reduced Q and by-passes cIII and cIV. Here, we used Ciona intestinalis AOX xenotopically expressed in mouse mitochondria to study how respiratory states impact the Q poise and how AOX may be used to restore respiration. Particularly interesting is our finding that electron input through succinate dehydrogenase (cII), but not NADH:ubiquinone oxidoreductase (cI), reduces the Q pool almost entirely (>90%) irrespective of the respiratory state. AOX enhances the forward electron transport (FET) from cII thereby decreasing reverse electron transport (RET) and ROS specifically when non-phosphorylating. AOX is not engaged with cI substrates, however, unless a respiratory inhibitor is added. This sheds new light on Q poise signaling, the biological role of cII which enigmatically is the only ETC complex absent from respiratory supercomplexes but yet participates in the tricarboxylic acid (TCA) cycle. Finally, we delineate potential risks and benefits arising from therapeutic AOX transfer.

    更新日期:2019-12-09
  • Stoichiometry of protein complexes in plant photosynthetic membranes
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-12-09
    Steven D. McKenzie, Iskander M. Ibrahim, Uma K. Aryal, Sujith Puthiyaveetil

    Hetero-oligomeric membrane protein complexes form the electron transport chain (ETC) of oxygenic photosynthesis. The ETC complexes undertake the light-driven vectorial electron and proton transport reactions, which generate energy-rich ATP and electron-rich NADPH molecules for carbon fixation. The rate of photosynthetic electron transport depends on the availability of photons and the relative abundance of electron transport complexes. The relative abundance of the two photosystems, critical for the quantum efficiency of photosynthesis in changing light quality conditions, has been determined successfully by optical methods. Due to the lack of spectroscopic signatures, however, relatively little is known about the stoichiometry of other non-photosystem complexes in plant photosynthetic membrane. Here we determine the ratios of all major thylakoid-bound ETC complexes in Arabidopsis by a label-free quantitative mass spectrometry technique. The calculated stoichiometries are consistent with known subunit composition of complexes and current estimates of photosystem and cytochrome b6f concentrations. The implications of these stoichiometries for photosynthetic light harvesting and the partitioning of electrons between the linear and cyclic electron transport pathways of photosynthesis are discussed.

    更新日期:2019-12-09
  • Fine-tuning of the respiratory complexes stability and supercomplexes assembly in cells defective of complex III
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-12-09
    Concetta V. Tropeano, Serena J. Aleo, Claudia Zanna, Marina Roberti, Letizia Scandiffio, Paola Loguercio Polosa, Jessica Fiori, Emanuele Porru, Aldo Roda, Valerio Carelli, Stefan Steimle, Fevzi Daldal, Michela Rugolo, Anna Ghelli
    更新日期:2019-12-09
  • Red-shifted chlorophyll a bands allow uphill energy transfer to photosystem II reaction centers in an aerial green alga, Prasiola crispa, harvested in Antarctica
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-12-09
    Makiko Kosugi, Shin-Ichiro Ozawa, Yuichiro Takahashi, Yasuhiro Kamei, Shigeru Itoh, Sakae Kudoh, Yasuhiro Kashino, Hiroyuki Koike

    An aerial green alga, Prasiola crispa (Lightf.) Menegh, which is known to form large colonies in Antarctic habitats, is subject to severe environmental stresses due to low temperature, draught and strong sunlight in summer. A considerable light-absorption by long-wavelength chlorophylls (LWC) at around 710 nm, which seem to consist of chlorophyll a, was detected in thallus of P. crispa harvested at a terrestrial environment in Antarctica. Absorption level at 710 nm against that at 680 nm was correlated with fluorescence emission intensity at 713 nm at room temperature and the 77 K fluorescence emission band from LWC was found to be emitted at 735 nm. We demonstrated that the LWC efficiently transfer excitation energy to photosystem II (PSII) reaction center from measurements of action spectra of photosynthetic oxygen evolution and P700 photo-oxidation. The global quantum yield of PSII excitation in thallus by far-red light was shown to be as high as by orange light, and the excitation balance between PSII and PSI was almost same in the two light sources. It is thus proposed that the LWC increase the photosynthetic productivity in the lower parts of overlapping thalli and contribute to the predominance of alga in the severe environment.

    更新日期:2019-12-09
  • Simulation of a nonphotochemical quenching in plant leaf under different light intensities
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-12-09
    Ekaterina Sukhova, Andrey Khlopkov, Vladimir Vodeneev, Vladimir Sukhov

    An analysis of photosynthetic response on action of stressors is an important problem, which can be solved by experimental and theoretical methods, including mathematical modeling of photosynthetic processes. The aim of our work was elaboration of a mathematical model, which simulated development of a nonphotochemical quenching under different light conditions. We analyzed two variants of the model: the first variant included a light-induced activation of the electron transport chain; in contrast, the second variant did not describe this activation. Both variants of the model described interactions between transitions from open reaction centers to closed ones (and vice versa) and development of the nonphotochemical quenching. Investigation of both variants of the model showed well qualitative and quantitative accordance between simulated and experimental changes in coefficient of the nophotochemical quenching which were analyzed under different light regimes: (i) the stepped increase of the light intensity without dark intervals between steps, (ii) periodical illuminations by different light intensities with constant durations which were separated by constant dark intervals, and (iii) periodical illuminations by the constant light intensity with different durations which were separated by different dark intervals. Thus, the model can be used for theoretical prediction of stress changes in photosynthesis under fluctuations in light intensity and search of optimal regimes of plant illumination.

    更新日期:2019-12-09
  • Decreased photosystem II activity facilitates acclimation to fluctuating light in the understory plant Paris polyphylla
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-12-09
    Hu Sun, Shi-Bao Zhang, Tao Liu, Wei Huang

    In forests, understory plants are usually exposed to sunflecks on timescales of seconds or minutes. However, it is unclear how understory plants acclimate to fluctuating light. In this study, we compared chlorophyll fluorescence, PSI redox state and the electrochromic shift signal under fluctuating light between an understory plant Paris polyphylla (Liliaceae) and a light-demanding plant Bletilla striata (Orchidaceae). Within the first seconds after transition from low to high light, PSI was highly oxidized in P. polyphylla but was highly reduced in B. striata, although both species could not generate a sufficient trans-thylakoid proton gradient (ΔpH). Furthermore, the outflow of electrons from PSI to O2 was not significant in P. polyphylla, as indicated by the P700 redox kinetics upon dark-to-light transition. Therefore, the different responses of PSI to fluctuating light between P. polyphylla and B. striata could not be explained by ΔpH formation or alternative electron transport. In contrast, upon a sudden transition from low to high light, electron flow from PSII was much lower in P. polyphylla than in B. striata, suggesting that the rapid oxidation of PSI in P. polyphylla was largely attributed to the lower PSII activity. We propose, for the first time, that down-regulation of PSII activity is an important strategy used by some understory angiosperms to cope with sunflecks.

    更新日期:2019-12-09
  • Plasticity of photosynthetic processes and the accumulation of secondary metabolites in plants in response to monochromatic light environments: A review
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-12-07
    Marco Landi, Marek Zivcak, Oksana Sytar, Marian Brestic, Suleyman I. Allakhverdiev

    Light spectra significantly influence plant metabolism, growth and development. Here, we review the effects of monochromatic blue, red and green light compared to those of multispectral light sources on the morpho-anatomical, photosynthetic and molecular traits of herbaceous plants. Emphasis is given to the effect of light spectra on the accumulation of secondary metabolites, which are important bioactive phytochemicals that determine the nutritional quality of vegetables. Overall, blue light may promote the accumulation of phenylpropanoid-based compounds without substantially affecting plant morpho-anatomical traits compared to the effects of white light. Red light, conversely, strongly alters plant morphology and physiology compared to that under white light without showing a consistent positive effect on secondary metabolism. Due to species-specific effects and the small shifts in the spectral band within the same color that can substantially affect plant growth and metabolism, it is conceivable that monochromatic light significantly affects not only plant photosynthetic performance but also the “quality” of plants by modulating the biosynthesis of photoprotective compounds.

    更新日期:2019-12-07
  • The oligomeric state of the Caldivirga maquilingensis type III sulfide:Quinone Oxidoreductase is required for membrane binding
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-12-06
    Andrea M. Lencina, Robert B. Gennis, Lici A. Schurig-Briccio

    Sulfide:quinone oxidoreductase (SQR) is a monotopic membrane flavoprotein present in all domains of life, with multiple roles including sulfide detoxification, homeostasis and energy generation by providing electrons to respiratory or photosynthetic electron transport chains. A type III SQR from the hyperthermophilic archeon Caldivirga maquilingensis has been previously characterized, and its C-terminal amphipathic helices were demonstrated to be responsible for membrane binding. Here, the oligomeric state of this protein was experimentally evaluated by size exclusion chromatography, native gels and crosslinking, and found to be a monomer-dimer-trimer equilibrium. Remarkably, mutant and truncated variants unable to bind to the membrane are able to maintain their oligomeric association. Thus, unlike other related monotopic membrane proteins, the region involved in membrane binding does not influence oligomerization. Furthermore, by studying heterodimers between the WT and mutants, it was concluded that membrane binding requires an oligomer with at least two copies of the protein with intact C-terminal amphipathic helices. A structural homology model of the C. maquilingensis SQR was used to define the flavin- and quinone-binding sites. CmGly12, CmGly16, CmAla77 and CmPro44 were determined to be important for flavin binding. Unexpectedly, CmGly299 is only important for quinone reduction despite its proximity to bound FAD. CmPhe337 and CmPhe362 are also important for quinone binding apparently by direct interaction with the quinone ring, whereas CmLys359, postulated to hydrogen bond to the quinone, seems to have a more structural role. The results presented differentiate the Type III CmSQR from some of its counterparts classified as Type I, II and III.

    更新日期:2019-12-07
  • The spatio-temporal organization of mitochondrial F1FO ATP synthase in cristae depends on its activity mode
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-11-27
    Kirill Salewskij, Bettina Rieger, Frances Hager, Tasnim Arroum, Patrick Duwe, Jimmy Villalta, Sara Colgiati, Christian P. Richter, Olympia E. Psathaki, José A. Enriquez, Timo Dellmann, Karin B. Busch
    更新日期:2019-11-28
  • The oxidation-reduction and electrocatalytic properties of CO dehydrogenase from Oligotropha carboxidovorans
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-11-14
    Palraj Kalimuthu, Mélanie Petitgenet, Dimitri Niks, Stephanie Dingwall, Jeffrey R. Harmer, Russ Hille, Paul V. Bernhardt

    CO dehydrogenase (CODH) from the Gram-negative bacterium Oligotropha carboxidovorans is a complex metalloenzyme of the xanthine oxidase family of molybdenum-containing enzymes, bearing a unique bimolecular Mo-S-Cu active site in addition to two [2Fe-2S] clusters (FeSI and FeSII) and one equivalent of FAD. CODH catalyzes the oxidation of CO to CO2 with the concomitant introduction of reducing equivalents into the quinone pool, thus enabling the organism to utilize CO as sole source of both carbon and energy. Using a variety of EPR monitored redox titrations and spectroelectrochemistry, we report the redox potentials of CO dehydrogenase at pH 7.2 as MoVI/V, MoV/IV, FeSI, FeSII, FAD/FADH and FADH/FADH− vs NHE. These potentials are systematically higher than the corresponding potentials seen for other members of the xanthine oxidase family of Mo enzymes, and are in line with CODH utilising the higher potential quinone pool as an electron acceptor instead of pyridine nucleotides. CODH is also active when immobilised on a modified Au working electrode as demonstrated by cyclic voltammetry in the presence of CO.

    更新日期:2019-11-14
  • 更新日期:2019-11-14
  • Structural changes at the surface of cytochrome c oxidase alter the proton-pumping stoichiometry
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-11-14
    Johan Berg, Jian Liu, Emelie Svahn, Shelagh Ferguson-Miller, Peter Brzezinski

    Data from earlier studies showed that minor structural changes at the surface of cytochrome c oxidase, near one of the proton-input pathways (the D pathway), result in dramatically decreased activity and a lower proton-pumping stoichiometry. To further investigate how changes around the D pathway orifice influence functionality of the enzyme, here we modified the nearby C-terminal loop of subunit I of the Rhodobacter sphaeroides cytochrome c oxidase. Removal of 16 residues form this flexible surface loop resulted in a decrease in the proton-pumping stoichiometry to <50% of that of the wild-type enzyme. Replacement of the protonatable residue Glu552, part of the same loop, by an Ala, resulted in a similar decrease in the proton-pumping stoichiometry without loss of the O2-reduction activity or changes in the proton-uptake kinetics. The data show that minor structural changes at the orifice of the D pathway, at a distance of ~40 Å from the proton gate of cytochrome c oxidase, may alter the proton-pumping stoichiometry of the enzyme.

    更新日期:2019-11-14
  • 更新日期:2019-11-14
  • Comparative ultrafast spectroscopy and structural analysis of OCP1 and OCP2 from Tolypothrix
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-11-14
    Valentyna Kuznetsova, Maria Agustina Dominguez-Martin, Han Bao, Sayan Gupta, Markus Sutter, Miroslav Kloz, Mateusz Rebarz, Martin Přeček, Yan Chen, Christopher J. Petzold, Corie Y. Ralston, Cheryl A. Kerfeld, Tomáš Polívka
    更新日期:2019-11-14
  • Integrated thermodynamic analysis of electron bifurcating [FeFe]-hydrogenase to inform anaerobic metabolism and H2 production
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-11-08
    Zackary J. Jay, Kristopher A. Hunt, Katherine J. Chou, Gerrit J. Schut, Pin-Ching Maness, Michael W.W. Adams, Ross P. Carlson
    更新日期:2019-11-11
  • Photochemical characterization of flavobacterial rhodopsin: The importance of the helix E region for heat stability
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-11-06
    SongI Han, Se-Hwan Kim, Jang-Chon Cho, Jaeho Song, Gwen Bleckner, Kwang-Hwan Jung

    Although many microbial rhodopsins have been discovered many of organisms in a variety of habitats, little is known about the property and diversity of rhodopsin in flavobacteria. Recent studies discovered that many proteorhodopsin (PR)-like proteins exist in genomes of flavobacteria. Following the isolation of a flavobacterial rhodopsins (FR) from the flavobacteria IMCC1997 from the East Sea of Korea, we characterized its photochemical features. We confirmed that the FR expression is induced by light in the IMCC1997 cell. Upon receiving light energy in vitro, the proton acceptor (D83) and donor (E94) of the FR translocate protons from intracellular to extracellular regions. Compared with proteorhodopsin (PR), the FR from IMCC 1997 cells is very unstable, which may be explained by their primary sequence differences. The ratio of all trans/13-cis retinal conformation does not influence this stability. To measure the stability of FR, we tested heat endurance at 70 °C and found that the heat endurance time of some FR mutants increased. Based upon these results, we found the helix E of this protein to be critical for the unstability of FR.

    更新日期:2019-11-07
  • Role of the two PsaE isoforms on O2 reduction at photosystem I in Arabidopsis thaliana
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-11-06
    Anja Krieger-Liszkay, Ginga Shimakawa, Pierre Sétif

    Leaves of Arabidopsis thaliana plants grown in short days (8 h light) generate more reactive oxygen species in the light than leaves of plants grown in long days (16 h light). The importance of the two PsaE isoforms of photosystem I, PsaE1 and PsaE2, for O2 reduction was studied in plants grown under these different growth regimes. In short day conditions a mutant affected in the amount of PsaE1 (psae1-1) reduced more efficiently O2 than a mutant lacking PsaE2 (psae2-1) as shown by spin trapping EPR spectroscopy on leaves and by following the kinetics of P700+ reduction in isolated photosystem I. In short day conditions higher O2 reduction protected photosystem II against photoinhibition in psae1-1. In contrast in long day conditions the presence of PsaE1 was clearly beneficial for photosynthetic electron transport and for the stability of the photosynthetic apparatus under photoinhibitory conditions. We conclude that the two PsaE isoforms have distinct functions and we propose that O2 reduction at photosystem I is beneficial for the plant under certain environmental conditions.

    更新日期:2019-11-06
  • In the respiratory chain of Escherichia coli cytochromes bd-I and bd-II are more sensitive to carbon monoxide inhibition than cytochrome bo3
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-11-04
    Elena Forte, Vitaliy B. Borisov, Sergey A. Siletsky, Maria Petrosino, Alessandro Giuffrè

    Bacteria can not only encounter carbon monoxide (CO) in their habitats but also produce the gas endogenously. Bacterial respiratory oxidases, thus, represent possible targets for CO. Accordingly, host macrophages were proposed to produce CO and release it into the surrounding microenvironment to sense viable bacteria through a mechanism that in Escherichia (E.) coli was suggested to involve the targeting of a bd-type respiratory oxidase by CO. The aerobic respiratory chain of E. coli possesses three terminal quinol:O2-oxidoreductases: the heme-copper oxidase bo3 and two copper-lacking bd-type oxidases, bd-I and bd-II. Heme-copper and bd-type oxidases differ in the mechanism and efficiency of proton motive force generation and in resistance to oxidative and nitrosative stress, cyanide and hydrogen sulfide. Here, we investigated at varied O2 concentrations the effect of CO gas on the O2 reductase activity of the purified cytochromes bo3, bd-I and bd-II of E. coli. We found that CO, in competition with O2, reversibly inhibits the three enzymes. The inhibition constants Ki for the bo3, bd-I and bd-II oxidases are 2.4 ± 0.3, 0.04 ± 0.01 and 0.2 ± 0.1 μM CO, respectively. Thus, in E. coli, bd-type oxidases are more sensitive to CO inhibition than the heme-copper cytochrome bo3. The possible physiological consequences of this finding are discussed.

    更新日期:2019-11-04
  • Identification of assembly precursors to photosystems emitting fluorescence at 683 nm and 687 nm by cryogenic fluorescence microspectroscopy
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-10-31
    Tomofumi Chiba, Yutaka Shibata

    Photosystem I (PSI) and photosystem II (PSII) play key roles in photoinduced electron-transfer reaction in oxygenic photosynthesis. Assemblies of these PSs can be initiated by illumination of the etiolated seedlings (greening). The study aimed to identify specific fluorescence spectral components relevant to PSI and PSII assembly intermediates emerging in greening seedlings of Zea mays, a typical C4 plant. The different PSII contents between the bundle sheath (BS) and mesophyll (M) cells were utilized to spectrally isolate the precursors to PSI and PSII. The greening Zea mays leaf thin sections were observed with the cryogenic microscope combined with a spectrometer. With the aid of the singular-value decomposition analysis, we could identify four independent fluorescent species, SAS677, SAS685, SAS683, and SAS687, named after their fluorescence peak wavelengths. SAS677 and SAS685 are the dominant components after the 30-minute greening, and the distributions of these components showed no clear differences between M and BS cells, indicating immature cell differentiation in this developing stage. On the other hand, the 1-hour greening resulted in reduced distributions of SAS683 in BS cells leading us to assign this species to PSII precursors. The 2-hour greening induced the enrichment of SAS687 in BS cells suggesting its PSI relevance. Similarity in the peak wavelengths of SAS683 and the reported reaction center of PSII implied their connection. SAS687 showed an intense sub-band at around 740 nm, which can be assigned to the emission from the red chlorophylls specific to the mature PSI.

    更新日期:2019-11-01
  • Fourier transform infrared and mass spectrometry analyses of a site-directed mutant of D1-Asp170 as a ligand to the water-oxidizing Mn4CaO5 cluster in photosystem II
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-10-31
    Tomomi Kitajima-Ihara, Takehiro Suzuki, Shin Nakamura, Yuichiro Shimada, Ryo Nagao, Naoshi Dohmae, Takumi Noguchi
    更新日期:2019-11-01
  • The BF4 and p71 antenna mutants from Chlamydomonas reinhardtii
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-10-28
    Sandrine Bujaldon, Natsumi Kodama, Mithun Kumar Rathod, Nicolas Tourasse, Shin-Ichiro Ozawa, Julien Sellés, Olivier Vallon, Yuichiro Takahashi, Francis-André Wollman

    Two pale green mutants of the green alga Chlamydomonas reinhardtii, which have been used over the years in many photosynthesis studies, the BF4 and p71 mutants, were characterized and their mutated gene identified in the nuclear genome. The BF4 mutant is defective in the insertase Alb3.1 whereas p71 is defective in cpSRP43. The two mutants showed strikingly similar deficiencies in most of the peripheral antenna proteins associated with either photosystem I or photosystem 2. As a result the two photosystems have a reduced antenna size with photosystem 2 being the most affected. Still up to 20% of the antenna proteins remain in these strains, with the heterodimer Lhca5/Lhca6 showing a lower sensitivity to these mutations. We discuss these phenotypes in light of those of other allelic mutants that have been described in the literature and suggest that eventhough the cpSRP route serves as the main biogenesis pathway for antenna proteins, there should be an escape pathway which remains to be genetically identified.

    更新日期:2019-10-28
  • Does the water-oxidizing Mn4CaO5 cluster regulate the redox potential of the primary quinone electron acceptor QA in photosystem II? A study by Fourier transform infrared spectroelectrochemistry
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-10-25
    Yuki Kato, Ayaka Ohira, Ryo Nagao, Takumi Noguchi

    Redox titration using fluorescence measurements of photosystem II (PSII) has long shown that impairment of the water-oxidizing Mn4CaO5 cluster upshifts the redox potential (Em) of the primary quinone electron acceptor QA by more than 100 mV, which has been proposed as a photoprotection mechanism of PSII. However, the molecular mechanism of this long-distance interaction between the Mn4CaO5 cluster and QA in PSII remains unresolved. In this study, we reinvestigated the effect of depletion of the Mn4CaO5 cluster on Em(QA−/QA) using Fourier transform infrared (FTIR) spectroelectrochemistry, which can directly monitor the redox state of QA at an intended potential. Light-induced FTIR difference measurements at a series of electrode potentials for intact and Mn-depleted PSII preparations from spinach and Thermosynechococcus elongatus showed that depletion of the Mn4CaO5 cluster hardly affected the Em(QA−/QA) values. In contrast, fluorescence spectroelectrochemical measurement using the same PSII sample, electrochemical cell, and redox mediators reproduced a large upshift of apparent Em upon Mn depletion, whereas a smaller shift was observed when weaker visible light was used for fluorescence excitation. Thus, the possibility was suggested that the measuring light for fluorescence disturbed the titration curve in Mn-depleted PSII, in contrast to no interference of infrared light with the PSII reactions in FTIR measurements. From these results, it was concluded that the Mn4CaO5 cluster does not directly regulate Em(QA−/QA) to control the redox reactions on the electron acceptor side of PSII.

    更新日期:2019-10-25
  • Remodeling of excitation energy transfer in extremophilic red algal PSI-LHCI complex during light adaptation
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-10-25
    Mateusz Abram, Rafał Białek, Sebastian Szewczyk, Jerzy Karolczak, Krzysztof Gibasiewicz, Joanna Kargul

    Photosynthetic PSI-LHCI complexes from an extremophilic red alga C. merolae grown under varying light regimes are characterized by decreasing size of LHCI antenna with increasing illumination intensity [1]. In this study we applied time-resolved fluorescence spectroscopy to characterize the kinetics of energy transfer processes in three types of PSI-LHCI supercomplexes isolated from the low (LL), medium (ML) and extreme high light (EHL) conditions. We show that the average rate of fluorescence decay is not correlated with the size of LHCI antenna and is twice faster in complexes isolated from ML-grown cells (~25–30 ps) than from both LL- and EHL-exposed cells (~50–55 ps). The difference is mainly due to a contribution of a long ~100-ps decay component detected only for the latter two PSI samples. We propose that the lack of this phase in ML complexes is caused by perfect coupling of this antenna to PSI core and lack of low-energy chlorophylls in LHCI. On the other hand, the presence of the slow, ~100-ps, fluorescence decay component in LL and EHL complexes may be due to the weak coupling between PSI core and LHCI antenna complex, and due to the presence of particularly low-energy or red chlorophylls in LHCI. Our study has revealed the remarkable functional flexibility of light harvesting strategies that have evolved in the extremophilic red algae in response to harsh or limiting light conditions involving accumulation of low energy chlorophylls that exert two distinct functions: as energy traps or as far-red absorbing light harvesting antenna, respectively.

    更新日期:2019-10-25
  • On the interface of light-harvesting antenna complexes and reaction centers in oxygenic photosynthesis
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-09-10
    Haijun Liu, Robert E. Blankenship

    Photosynthetic pigment-protein complexes (PPCs) accomplish light-energy capture and photochemistry in natural photosynthesis. In this review, we examine three pigment protein complexes in oxygenic photosynthesis: light-harvesting antenna complexes and two reaction centers: Photosystem II (PSII), and Photosystem I (PSI). Recent technological developments promise unprecedented insights into how these multi–component protein complexes are assembled into higher order structures and thereby execute their function. Furthermore, the interfacial domain between light-harvesting antenna complexes and PSII, especially the potential roles of the structural loops from CP29 and the PB–loop of ApcE in higher plant and cyanobacteria, respectively, are discussed. It is emphasized that the structural nuances are required for the structural dynamics and consequently for functional regulation in response to an ever–changing and challenging environment.

    更新日期:2019-10-23
  • Photosynthetic regulation under fluctuating light in field-grown Cerasus cerasoides: A comparison of young and mature leaves
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-08-29
    Ying-Jie Yang, Shi-Bao Zhang, Ji-Hua Wang, Wei Huang

    Photosystem I (PSI) is a potential target of photoinhibition under fluctuating light. However, photosynthetic regulation under fluctuating light in field-grown plants is little known. Furthermore, it is unclear how young leaves protect PSI against fluctuating light under natural field conditions. In the present study, we examined chlorophyll fluorescence, P700 redox state and the electrochromic shift signal in the young and mature leaves of field-grown Cerasus cerasoides (Rosaceae). Within the first seconds after any increase in light intensity, young leaves showed higher proton gradient (ΔpH) across the thylakoid membranes than the mature leaves, preventing over-reduction of PSI in the young leaves. As a result, PSI was more tolerant to fluctuating light in the young leaves than in the mature leaves. Interestingly, after transition from low to high light, the activity of cyclic electron flow (CEF) in young leaves increased first to a high level and then decreased to a stable value, while this rapid stimulation of CEF was not observed in the mature leaves. Furthermore, the over-reduction of PSI significantly stimulated CEF in the young leaves but not in the mature leaves. Taken together, within the first seconds after any increase in illumination, the stimulation of CEF favors the rapid lumen acidification and optimizes the PSI redox state in the young leaves, protecting PSI against photoinhibition under fluctuating light in field-grown plants.

    更新日期:2019-10-23
  • Regulation of photosynthetic cyclic electron flow pathways by adenylate status in higher plant chloroplasts
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-09-11
    Nicholas Fisher, Terry M. Bricker, David M. Kramer

    Cylic electron flow (CEF) around Photosystem I in photosynthetic eukaryotes is likely to be necessary to augment ATP production, rapidly- and precisely balancing the plastid ATP/NADPH energy budget to meet the demands of downstream metabolism. Many regulatory aspects of this process are unclear. Here we demonstrate that the higher plant plastid NADH/Fd:plastoquinone reductase (NDH) and proposed PGR5/PGRL1 ferredoxin:plastoquinone reductase (FQR) pathways of CEF are strongly, rapidly and reversibly inhibited in vitro by ATP with Ki values of 670 μM and 240 μM respectively, within the range of physiological changes in ATP concentrations. Control experiments ruled out effects on secondary reactions, e.g. FNR- and cytochrome b6f activity, nonphotochemical quenching of chlorophyll fluorescence etc., supporting the view that ATP is an inhibitor of CEF and its associated pmf generation and subsequent ATP production. The effects are specific to ATP, with the ATP analog AMP-PNP showing little inhibitory effect, and ADP inhibiting only at higher concentrations. For the FQR pathway, inhibition was found to be classically competitive with Fd, and the NDH pathway showing partial competition with Fd. We propose a straightforward model for regulation of CEF in plants in which CEF is activated under conditions when stromal ATP low, but is downregulated as ATP levels build up, allowing for effective ATP homeostasis. The differences in Ki values suggest a two-tiered regulatory system, where the highly efficient proton pumping NDH is activated with moderate decreases in ATP, with the less energetically-efficient FQR pathway being activated under more severe ATP depletion.

    更新日期:2019-10-23
  • Characterization and X-ray structure of the NADH-dependent coenzyme A disulfide reductase from Thermus thermophilus
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-09-11
    Andrea M. Lencina, Juergen Koepke, Julia Preu, Cornelia Muenke, Robert B. Gennis, Hartmut Michel, Lici A. Schurig-Briccio

    The crystal structure of the enzyme previously characterized as a type-2 NADH:menaquinone oxidoreductase (NDH-2) from Thermus thermophilus has been solved at a resolution of 2.9 Å and revealed that this protein is, in fact, a coenzyme A-disulfide reductase (CoADR). Coenzyme A (CoASH) replaces glutathione as the major low molecular weight thiol in Thermus thermophilus and is maintained in the reduced state by this enzyme (CoADR). Although the enzyme does exhibit NADH:menadione oxidoreductase activity expected for NDH-2 enzymes, the specific activity with CoAD as an electron acceptor is about 5-fold higher than with menadione. Furthermore, the crystal structure contains coenzyme A covalently linked Cys44, a catalytic intermediate (Cys44-S-S-CoA) reduced by NADH via the FAD cofactor. Soaking the crystals with menadione shows that menadione can bind to a site near the redox active FAD, consistent with the observed NADH:menadione oxidoreductase activity. CoADRs from other species were also examined and shown to have measurable NADH:menadione oxidoreductase activity. Although a common feature of this family of enzymes, no biological relevance is proposed. The CoADR from T. thermophilus is a soluble homodimeric enzyme. Expression of the recombinant TtCoADR at high levels in E. coli results in a small fraction that co-purifies with the membrane fraction, which was used previously to isolate the enzyme wrongly identified as a membrane-bound NDH-2. It is concluded that T. thermophilus does not contain an authentic NDH-2 component in its aerobic respiratory chain.

    更新日期:2019-10-23
  • An alternative plant-like cyanobacterial ferredoxin with unprecedented structural and functional properties
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-09-12
    Taiki Motomura, Lidia Zuccarello, Pierre Sétif, Alain Boussac, Yasufumi Umena, David Lemaire, Jatindra N. Tripathy, Miwa Sugiura, Rainer Hienerwadel, Jian-Ren Shen, Catherine Berthomieu

    Photosynthetic [2Fe-2S] plant-type ferredoxins have a central role in electron transfer between the photosynthetic chain and various metabolic pathways. Several genes are coding for [2Fe2S] ferredoxins in cyanobacteria, with four in the thermophilic cyanobacterium Thermosynechococcus elongatus. The structure and functional properties of the major ferredoxin Fd1 are well known but data on the other ferredoxins are scarce. We report the structural and functional properties of a novel minor type ferredoxin, Fd2 of T. elongatus, homologous to Fed4 from Synechocystis sp. PCC 6803. Remarkably, the midpoint potential of Fd2, Em = −440 mV, is lower than that of Fd1, Em = −372 mV. However, while Fd2 can efficiently react with photosystem I or nitrite reductase, time-resolved spectroscopy shows that Fd2 has a very low capacity to reduce ferredoxin-NADP+ oxidoreductase (FNR). These unique Fd2 properties are discussed in relation with its structure, solved at 1.38 Å resolution. The Fd2 structure significantly differs from other known ferredoxins structures in loop 2, N-terminal region, hydrogen bonding networks and surface charge distributions. UV–Vis, EPR, and Mid- and Far-IR data also show that the electronic properties of the [2Fe2S] cluster of Fd2 and its interaction with the protein differ from those of Fd1 both in the oxidized and reduced states. The structural analysis allows to propose that valine in the motif Cys53ValAsnCys56 of Fd2 and the specific orientation of Phe72, explain the electron transfer properties of Fd2. Strikingly, the nature of these residues correlates with different phylogenetic groups of cyanobacterial Fds. With its low redox potential and its discrimination against FNR, Fd2 exhibits a unique capacity to direct efficiently photosynthetic electrons to metabolic pathways not dependent on FNR.

    更新日期:2019-10-23
  • Tuning antenna function through hydrogen bonds to chlorophyll a
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-08-30
    Manuel J. Llansola-Portoles, Fei Li, Pengqi Xu, Simona Streckaite, Cristian Ilioaia, Chunhong Yang, Andrew Gall, Andrew A. Pascal, Roberta Croce, Bruno Robert

    We describe a molecular mechanism tuning the functional properties of chlorophyll a (Chl-a) molecules in photosynthetic antenna proteins. Light-harvesting complexes from photosystem II in higher plants – specifically LHCII purified with α- or β-dodecyl-maltoside, along with CP29 – were probed by low-temperature absorption and resonance Raman spectroscopies. We show that hydrogen bonding to the conjugated keto carbonyl group of protein-bound Chl-a tunes the energy of its Soret and Qy absorption transitions, inducing red-shifts that are proportional to the strength of the hydrogen bond involved. Chls-a with non-H-bonded keto C131 groups exhibit the blue-most absorption bands, while both transitions are progressively red-shifted with increasing hydrogen-bonding strength – by up 382 & 605 cm−1 in the Qy and Soret band, respectively. These hydrogen bonds thus tune the site energy of Chl-a in light-harvesting proteins, determining (at least in part) the cascade of energy transfer events in these complexes.

    更新日期:2019-10-23
  • Extensive remodeling of the photosynthetic apparatus alters energy transfer among photosynthetic complexes when cyanobacteria acclimate to far-red light
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-08-14
    Ming-Yang Ho, Dariusz M. Niedzwiedzki, Craig MacGregor-Chatwin, Gary Gerstenecker, C. Neil Hunter, Robert E. Blankenship, Donald A. Bryant

    Some cyanobacteria remodel their photosynthetic apparatus by a process known as Far-Red Light Photoacclimation (FaRLiP). Specific subunits of the phycobilisome (PBS), photosystem I (PSI), and photosystem II (PSII) complexes produced in visible light are replaced by paralogous subunits encoded within a conserved FaRLiP gene cluster when cells are grown in far-red light (FRL; λ = 700–800 nm). FRL-PSII complexes from the FaRLiP cyanobacterium, Synechococcus sp. PCC 7335, were purified and shown to contain Chl a, Chl d, Chl f, and pheophytin a, while FRL-PSI complexes contained only Chl a and Chl f. The spectroscopic properties of purified photosynthetic complexes from Synechococcus sp. PCC 7335 were determined individually, and energy transfer kinetics among PBS, PSII, and PSI were analyzed by time-resolved fluorescence (TRF) spectroscopy. Direct energy transfer from PSII to PSI was observed in cells (and thylakoids) grown in red light (RL), and possible routes of energy transfer in both RL- and FRL-grown cells were inferred. Three structural arrangements for RL-PSI were observed by atomic force microscopy of thylakoid membranes, but only arrays of trimeric FRL-PSI were observed in thylakoids from FRL-grown cells. Cells grown in FRL synthesized the FRL-specific complexes but also continued to synthesize some PBS and PSII complexes identical to those produced in RL. Although the light-harvesting efficiency of photosynthetic complexes produced in FRL might be lower in white light than the complexes produced in cells acclimated to white light, the FRL-complexes provide cells with the flexibility to utilize both visible and FRL to support oxygenic photosynthesis. This article is part of a Special Issue entitled Light harvesting, edited by Dr. Roberta Croce.

    更新日期:2019-10-23
  • Fate of oxygen species from O2 activation at dimetal cofactors in an oxidase enzyme revealed by 57Fe nuclear resonance X-ray scattering and quantum chemistry
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-08-05
    Stefan Mebs, Vivek Srinivas, Ramona Kositzki, Julia J. Griese, Martin Högbom, Michael Haumann
    更新日期:2019-10-23
  • Functional analysis of coiled-coil domains of MCU in mitochondrial calcium uptake
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-08-05
    Takenori Yamamoto, Mizune Ozono, Akira Watanabe, Kosuke Maeda, Atsushi Nara, Mei Hashida, Yusuke Ido, Yuka Hiroshima, Akiko Yamada, Hiroshi Terada, Yasuo Shinohara
    更新日期:2019-10-23
  • Successes & challenges in the atomistic modeling of light-harvesting and its photoregulation
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-08-03
    Lorenzo Cupellini, Mattia Bondanza, Michele Nottoli, Benedetta Mennucci
    更新日期:2019-10-23
  • Pigment-protein complexes are organized into stable microdomains in cyanobacterial thylakoids
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-07-22
    A. Strašková, G. Steinbach, G. Konert, E. Kotabová, J. Komenda, M. Tichý, R. Kaňa
    更新日期:2019-10-23
  • 更新日期:2019-10-23
  • The amazing phycobilisome
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-07-12
    Noam Adir, Shira Bar-Zvi, Dvir Harris

    Cyanobacteria and red-algae share a common light-harvesting complex which is different than all other complexes that serve as photosynthetic antennas – the Phycobilisome (PBS). The PBS is found attached to the stromal side of thylakoid membranes, filling up most of the gap between individual thylakoids. The PBS self assembles from similar homologous protein units that are soluble and contain conserved cysteine residues that covalently bind the light absorbing chromophores, linear tetra-pyrroles. Using similar construction principles, the PBS can be as large as 16.8 MDa (68×45×39nm), as small as 1.2 MDa (24 × 11.5 × 11.5 nm), and in some unique cases smaller still. The PBS can absorb light between 450 nm to 650 nm and in some cases beyond 700 nm, depending on the species, its composition and assembly. In this review, we will present new observations and structures that expand our understanding of the distinctive properties that make the PBS an amazing light harvesting system. At the end we will suggest why the PBS, for all of its excellent properties, was discarded by photosynthetic organisms that arose later in evolution such as green algae and higher plants.

    更新日期:2019-10-23
  • Light stress in green and red Planktothrix strains: The orange carotenoid protein and its related photoprotective mechanism
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-06-20
    Chakib Djediat, Kathleen Feilke, Arthur Brochard, Lucie Caramelle, Sandra Kim Tiam, Pierre Sétif, Theo Gauvrit, Claude Yéprémian, Adjélé Wilson, Léa Talbot, Benjamin Marie, Diana Kirilovsky, Cécile Bernard
    更新日期:2019-10-23
  • Structural analysis and comparison of light-harvesting complexes I and II
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-06-20
    Xiaowei Pan, Peng Cao, Xiaodong Su, Zhenfeng Liu, Mei Li

    Photosynthesis is a fundamental biological process involving the conversion of solar energy into chemical energy. The initial photochemical and photophysical events of photosynthesis are mediated by photosystem II (PSII) and photosystem I (PSI). Both PSII and PSI are multi-subunit supramolecular machineries composed of a core complex and a peripheral antenna system. The antenna system serves to capture light energy and transfer it to the core efficiently. Both PSII and PSI in the green lineage (plants and green algae) and PSI in red algae have an antenna system comprising a series of chlorophyll- and carotenoid-binding membrane proteins belonging to the light-harvesting complex (LHC) superfamily, including LHCII and LHCI. However, the antenna size and subunit composition vary considerably in the two photosystems from diverse organisms. On the basis of the plant and algal LHCII and LHCI structures that have been solved by X-ray crystallography and single-particle cryo-electron microscopy we review the detailed structural features and characteristic pigment properties of these LHCs in PSII and PSI. This article is part of a Special Issue entitled Light harvesting, edited by Dr. Roberta Croce.

    更新日期:2019-10-23
  • The relevance of dynamic thylakoid organisation to photosynthetic regulation
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-06-20
    Matthew P. Johnson, Emilie Wientjes
    更新日期:2019-10-23
  • Monomeric light harvesting complexes enhance excitation energy transfer from LHCII to PSII and control their lateral spacing in thylakoids
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-06-19
    Luca Dall'Osto, Stefano Cazzaniga, Dario Zappone, Roberto Bassi

    Proper assembly of plant photosystem II, in the appressed region of thylakoids, allows for both efficient light harvesting and the dissipation of excitation energy absorbed in excess. The core moiety of wild type supercomplex is associated with monomeric antennae that, in turn, bind peripheral trimeric LHCII complexes. Acclimation to light environment dynamics involves structural plasticity within PSII-LHCs supercomplexes, including depletion in LHCII and CP24. Here, we report on the acclimation of NoM, an Arabidopsis mutant lacking monomeric LHCs but retaining LHCII trimer. Lack of monomeric LHCs impaired the operation of both photosynthetic electron transport and state transitions, despite the fact that NoM underwent a compensatory over-accumulation of the LHCII complement compared to the wild type. Mutant plants displayed stunted growth compared to the wild type when probed over a range of light conditions. When exposed to short-term excess light, NoM showed higher photosensitivity and enhanced singlet oxygen release than the wild type, whereas long-term acclimation under stress conditions was unaffected. Analysis of pigment-binding supercomplexes showed that the absence of monomeric LHCs did affect the macro-organisation of photosystems: large PSI-LHCII megacomplexes were more abundant in NoM, whereas the assembly of PSII-LHCs supercomplexes was impaired. Observation by electron microscopy (EM) and image analysis of thylakoids highlighted impaired granal stacking and membrane organisation, with a heterogeneous distribution of PSII and LHCII compared to the wild type. It is concluded that monomeric LHCs are critical for the structural and functional optimisation of the photosynthetic apparatus.

    更新日期:2019-10-23
  • Light harvesting complexes in chlorophyll c-containing algae
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-05-31
    Claudia Büchel

    Besides the so-called ‘green lineage’ of eukaryotic photosynthetic organisms that include vascular plants, a huge variety of different algal groups exist that also harvest light by means of membrane intrinsic light harvesting proteins (Lhc). The main taxa of these algae are the Cryptophytes, Haptophytes, Dinophytes, Chromeridae and the Heterokonts, the latter including diatoms, brown algae, Xanthophyceae and Eustigmatophyceae amongst others. Despite the similarity in Lhc proteins between vascular plants and these algae, pigmentation is significantly different since no Chl b is bound, but often replaced by Chl c, and a large diversity in carotenoids functioning in light harvesting and/or photoprotection is present. Due to the presence of Chl c in most of the taxa the name ‘Chl c-containing organisms’ has become common, however, Chl b-less is more precise since some harbour Lhc proteins that only bind one type of Chl, Chl a. In recent years huge progress has been made about the occurrence and function of Lhc in diatoms, so-called fucoxanthin chlorophyll proteins (FCP), where also the first molecular structure became available recently. In addition, especially energy transfer amongst the unusual pigments bound was intensively studied in many of these groups. This review summarises the present knowledge about the molecular structure, the arrangement of the different Lhc in complexes, the excitation energy transfer abilities and the involvement in photoprotection of the different Lhc systems in the so-called Chl c-containing organisms. This article is part of a Special Issue entitled Light harvesting, edited by Dr. Roberta Croce.

    更新日期:2019-10-23
  • Enhanced NPQ affects long-term acclimation in the spring ephemeral Berteroa incana
    BBA Bioenerg. (IF 4.441) Pub Date : 2019-03-15
    Sam Wilson, Alexander V. Ruban

    The spring ephemeral Berteroa incana is a familial relative of Arabidopsis thaliana and thrives in a diverse range of terrestrial ecosystems. Within this study, the novel chlorophyll fluorescence parameter of photochemical quenching in the dark (qPd) was used to measure the redox state of the primary quinone electron acceptor (QA) in order to estimate the openness of photosystem II (PSII) reaction centres (RC). From this, the early onset of photoinactivation can be sensitively quantified alongside the light tolerance of PSII and the photoprotective efficiency of nonphotochemical quenching (NPQ). This study shows that, with regards to A. thaliana, NPQ is enhanced in B. incana in both low-light (LL) and high-light (HL) acclimation states. Moreover, light tolerance is increased by up to 500%, the rate of photoinactivation is heavily diminished, and the ability to recover from light stress is enhanced in B. incana, relative to A. thaliana. This is due to faster synthesis of zeaxanthin and a larger xanthophyll cycle (XC) pool available for deepoxidation. Moreover, preferential energy transfer via CP47 around the RC further enhances efficient photoprotection. As a result, a high functional cross-section of photosystem II is maintained and is not downregulated when B. incana is acclimated to HL. A greater capacity for protective NPQ allows B. incana to maintain an enhanced light-harvesting capability when acclimated to a range of light conditions. This enhancement of flexible short-term protection saves the metabolic cost of long-term acclimatory changes.

    更新日期:2019-10-23
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