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Robert E. Blankenship - One of the best experts on this subject based on the ideXlab platform.
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Polymer-Chlorosome Nanocomposites Consisting of Non-Native Combinations of Self-Assembling Bacteriochlorophylls.
Langmuir : the ACS journal of surfaces and colloids, 2017Co-Authors: Gregory S. Orf, Gabriel A. Montaño, Donald A Bryant, Marcus Tank, Aaron M. Collins, Dariusz M. Niedzwiedzki, Vera Thiel, Adam Kell, Robert E. BlankenshipAbstract:Chlorosomes are one of the characteristic light-harvesting antennas from green sulfur bacteria. These complexes represent a unique paradigm: self-assembly of bacteriochlorophyll pigments within a lipid monolayer without the influence of protein. Because of their large size and reduced complexity, they have been targeted as models for the development of bioinspired light-harvesting arrays. We report the production of biohybrid light-harvesting nanocomposites mimicking Chlorosomes, composed of amphiphilic diblock copolymer membrane bodies that incorporate thousands of natural self-assembling bacteriochlorophyll molecules derived from green sulfur bacteria. The driving force behind the assembly of these polymer–Chlorosome nanocomposites is the transfer of the mixed raw materials from the organic to the aqueous phase. We incorporated up to five different self-assembling pigment types into single nanocomposites that mimic Chlorosome morphology. We establish that the copolymer-BChl self-assembly process works s...
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Polymer–Chlorosome Nanocomposites Consisting of Non-Native Combinations of Self-Assembling Bacteriochlorophylls
2017Co-Authors: Gregory S. Orf, Donald A Bryant, Marcus Tank, Aaron M. Collins, Dariusz M. Niedzwiedzki, Vera Thiel, Adam Kell, Gabriel A. Montaño, Robert E. BlankenshipAbstract:Chlorosomes are one of the characteristic light-harvesting antennas from green sulfur bacteria. These complexes represent a unique paradigm: self-assembly of bacteriochlorophyll pigments within a lipid monolayer without the influence of protein. Because of their large size and reduced complexity, they have been targeted as models for the development of bioinspired light-harvesting arrays. We report the production of biohybrid light-harvesting nanocomposites mimicking Chlorosomes, composed of amphiphilic diblock copolymer membrane bodies that incorporate thousands of natural self-assembling bacteriochlorophyll molecules derived from green sulfur bacteria. The driving force behind the assembly of these polymer–Chlorosome nanocomposites is the transfer of the mixed raw materials from the organic to the aqueous phase. We incorporated up to five different self-assembling pigment types into single nanocomposites that mimic Chlorosome morphology. We establish that the copolymer-BChl self-assembly process works smoothly even when non-native combinations of BChl homologues are included. Spectroscopic characterization revealed that the different types of self-assembling pigments participate in ultrafast energy transfer, expanding beyond single chromophore constraints of the natural Chlorosome system. This study further demonstrates the utility of flexible short-chain, diblock copolymers for building scalable, tunable light-harvesting arrays for technological use and allows for an in vitro analysis of the flexibility of natural self-assembling chromophores in unique and controlled combinations
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Chlorosome antenna complexes from green photosynthetic bacteria
Photosynthesis Research, 2013Co-Authors: Robert E. BlankenshipAbstract:Chlorosomes are the distinguishing light-harvesting antenna complexes that are found in green photosynthetic bacteria. They contain bacteriochlorophyll (BChl) c , d , e in natural organisms, and recently through mutation, BChl f , as their principal light-harvesting pigments. In Chlorosomes, these pigments self-assemble into large supramolecular structures that are enclosed inside a lipid monolayer to form an ellipsoid. The pigment assembly is dictated mostly by pigment–pigment interactions as opposed to protein–pigment interactions. On the bottom face of the Chlorosome, the CsmA protein aggregates into a paracrystalline baseplate with BChl a , and serves as the interface to the next energy acceptor in the system. The exceptional light-harvesting ability at very low light conditions of Chlorosomes has made them an attractive subject of study for both basic and applied science. This review, incorporating recent advancements, considers several important aspects of Chlorosomes: pigment biosynthesis, organization of pigments and proteins, spectroscopic properties, and applications to bio-hybrid and bio-inspired devices.
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Comparison of the physical characteristics of Chlorosomes from three different phyla of green phototrophic bacteria.
Biochimica et biophysica acta, 2013Co-Authors: Peter G. Adams, Robert E. Blankenship, Donald A Bryant, Yusuke Tsukatani, Marcus Tank, Ashley J. Cadby, Benjamin Robinson, Jianzhong Wen, C. Neil HunterAbstract:Abstract Chlorosomes, the major antenna complexes in green sulphur bacteria, filamentous anoxygenic phototrophs, and phototrophic acidobacteria, are attached to the cytoplasmic side of the inner cell membrane and contain thousands of bacteriochlorophyll (BChl) molecules that harvest light and channel the energy to membrane-bound reaction centres. Chlorosomes from phototrophs representing three different phyla, Chloroflexus (Cfx.) aurantiacus, Chlorobaculum (Cba.) tepidum and the newly discovered “Candidatus (Ca.) Chloracidobacterium (Cab.) thermophilum” were analysed using PeakForce Tapping atomic force microscopy (PFT-AFM). Gentle PFT-AFM imaging in buffered solutions that maintained the Chlorosomes in a near-native state revealed ellipsoids of variable size, with surface bumps and undulations that differ between individual Chlorosomes. Cba. tepidum Chlorosomes were the largest (133 × 57 × 36 nm; 141,000 nm3 volume), compared with Chlorosomes from Cfx. aurantiacus (120 × 44 × 30 nm; 84,000 nm3) and Ca. Cab. thermophilum (99 × 40 × 31 nm; 65,000 nm3). Reflecting the contributions of thousands of pigment–pigment stacking interactions to the stability of these supramolecular assemblies, analysis by nanomechanical mapping shows that Chlorosomes are highly stable and that their integrity is disrupted only by very strong forces of 1000–2000 pN. AFM topographs of Ca. Cab. thermophilum Chlorosomes that had retained their attachment to the cytoplasmic membrane showed that this membrane dynamically changes shape and is composed of protrusions of up to 30 nm wide and 6 nm above the mica support, possibly representing different protein domains. Spectral imaging revealed significant heterogeneity in the fluorescence emission of individual Chlorosomes, likely reflecting the variations in BChl c homolog composition and internal arrangements of the stacked BChls within each Chlorosome.
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Structural and Functional Roles of Carotenoids in Chlorosomes
Journal of bacteriology, 2013Co-Authors: Jakub Psencik, Robert E. Blankenship, Pasi Laurinmaki, Ritva Serimaa, Roman Tuma, Aaron M. Collins, Mika Torkkeli, Juan B. Arellano, Benita Löflund, Sarah J ButcherAbstract:Chlorosomes are large light-harvesting complexes found in three phyla of anoxygenic photosynthetic bacteria. Chlorosomes are primarily composed of self-assembling pigment aggregates. In addition to the main pigment, bacteriochlorophyll c, d, or e, Chlorosomes also contain variable amounts of carotenoids. Here, we use X-ray scattering and electron cryomicroscopy, complemented with absorption spectroscopy and pigment analysis, to compare the morphologies, structures, and pigment compositions of Chlorosomes from Chloroflexus aurantiacus grown under two different light conditions and Chlorobaculum tepidum. High-purity Chlorosomes from C. aurantiacus contain about 20% more carotenoid per bacteriochlorophyll c molecule when grown under low light than when grown under high light. This accentuates the light-harvesting function of carotenoids, in addition to their photoprotective role. The low-light Chlorosomes are thicker due to the overall greater content of pigments and contain domains of lamellar aggregates. Experiments where carotenoids were selectively extracted from intact Chlorosomes using hexane proved that they are located in the interlamellar space, as observed previously for species belonging to the phylum Chlorobi. A fraction of the carotenoids are localized in the baseplate, where they are bound differently and cannot be removed by hexane. In C. tepidum, carotenoids cannot be extracted by hexane even from the Chlorosome interior. The chemical structure of the pigments in C. tepidum may lead to π-π interactions between carotenoids and bacteriochlorophylls, preventing carotenoid extraction. The results provide information about the nature of interactions between bacteriochlorophylls and carotenoids in the protein-free environment of the Chlorosome interior.
Donald A Bryant - One of the best experts on this subject based on the ideXlab platform.
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Polymer-Chlorosome Nanocomposites Consisting of Non-Native Combinations of Self-Assembling Bacteriochlorophylls.
Langmuir : the ACS journal of surfaces and colloids, 2017Co-Authors: Gregory S. Orf, Gabriel A. Montaño, Donald A Bryant, Marcus Tank, Aaron M. Collins, Dariusz M. Niedzwiedzki, Vera Thiel, Adam Kell, Robert E. BlankenshipAbstract:Chlorosomes are one of the characteristic light-harvesting antennas from green sulfur bacteria. These complexes represent a unique paradigm: self-assembly of bacteriochlorophyll pigments within a lipid monolayer without the influence of protein. Because of their large size and reduced complexity, they have been targeted as models for the development of bioinspired light-harvesting arrays. We report the production of biohybrid light-harvesting nanocomposites mimicking Chlorosomes, composed of amphiphilic diblock copolymer membrane bodies that incorporate thousands of natural self-assembling bacteriochlorophyll molecules derived from green sulfur bacteria. The driving force behind the assembly of these polymer–Chlorosome nanocomposites is the transfer of the mixed raw materials from the organic to the aqueous phase. We incorporated up to five different self-assembling pigment types into single nanocomposites that mimic Chlorosome morphology. We establish that the copolymer-BChl self-assembly process works s...
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Polymer–Chlorosome Nanocomposites Consisting of Non-Native Combinations of Self-Assembling Bacteriochlorophylls
2017Co-Authors: Gregory S. Orf, Donald A Bryant, Marcus Tank, Aaron M. Collins, Dariusz M. Niedzwiedzki, Vera Thiel, Adam Kell, Gabriel A. Montaño, Robert E. BlankenshipAbstract:Chlorosomes are one of the characteristic light-harvesting antennas from green sulfur bacteria. These complexes represent a unique paradigm: self-assembly of bacteriochlorophyll pigments within a lipid monolayer without the influence of protein. Because of their large size and reduced complexity, they have been targeted as models for the development of bioinspired light-harvesting arrays. We report the production of biohybrid light-harvesting nanocomposites mimicking Chlorosomes, composed of amphiphilic diblock copolymer membrane bodies that incorporate thousands of natural self-assembling bacteriochlorophyll molecules derived from green sulfur bacteria. The driving force behind the assembly of these polymer–Chlorosome nanocomposites is the transfer of the mixed raw materials from the organic to the aqueous phase. We incorporated up to five different self-assembling pigment types into single nanocomposites that mimic Chlorosome morphology. We establish that the copolymer-BChl self-assembly process works smoothly even when non-native combinations of BChl homologues are included. Spectroscopic characterization revealed that the different types of self-assembling pigments participate in ultrafast energy transfer, expanding beyond single chromophore constraints of the natural Chlorosome system. This study further demonstrates the utility of flexible short-chain, diblock copolymers for building scalable, tunable light-harvesting arrays for technological use and allows for an in vitro analysis of the flexibility of natural self-assembling chromophores in unique and controlled combinations
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Glycolipid analyses of light-harvesting Chlorosomes from envelope protein mutants of Chlorobaculum tepidum
Photosynthesis Research, 2016Co-Authors: Yusuke Tsukatani, Donald A Bryant, Tadashi Mizoguchi, Jennifer Thweatt, Marcus Tank, Hitoshi TamiakiAbstract:Chlorosomes are large and efficient light-harvesting organelles in green photosynthetic bacteria, and they characteristically contain large numbers of bacteriochlorophyll c, d, or e molecules. Self-aggregated bacteriochlorophyll pigments are surrounded by a monolayer envelope membrane comprised of glycolipids and Csm proteins. Here, we analyzed glycolipid compositions of Chlorosomes from the green sulfur bacterium Chlorobaculum tepidum mutants lacking one, two, or three Csm proteins by HPLC equipped with an evaporative light-scattering detector. The ratio of monogalactosyldiacylglyceride (MGDG) to rhamnosylgalactosyldiacylglyceride (RGDG) was smaller in Chlorosomes from mutants lacking two or three proteins in CsmC/D/H motif family than in Chlorosomes from the wild-type, whereas Chlorosomes lacking CsmIJ showed relatively less RGDG than MGDG. The results suggest that the CsmC, CsmD, CsmH, and other Chlorosome proteins are involved in organizing MGDG and RGDG and thereby affect the size and shape of the Chlorosome.
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Structure of Light-Harvesting Aggregates in Individual Chlorosomes
2016Co-Authors: Lisa M. Günther, Donald A Bryant, Marcus Tank, Marc Jendrny, Erik A. Bloemsma, Gert T. Oostergetel, Jasper Knoester, Jürgen KöhlerAbstract:Among all photosynthetic organisms, green bacteria have evolved one of the most efficient light-harvesting antenna, the Chlorosome, that contains hundreds of thousands of bacteriochlorophyll molecules, allowing these bacteria to grow photosynthetically by absorbing only a few photons per bacteriochlorophyll molecule per day. In contrast to other photosynthetic light-harvesting antenna systems, for which a protein scaffold imposes the proper positioning of the chromophores with respect to each other, in Chlorosomes, this is accomplished solely by self-assembly. This has aroused enormous interest in the structure–function relations of these assemblies, as they can serve as blueprints for artificial light harvesting systems. In spite of these efforts, conclusive structural information is not available yet, reflecting the sample heterogeneity inherent to the natural system. Here we combine mutagenesis, polarization-resolved single-particle fluorescence–excitation spectroscopy, cryo-electron microscopy, and theoretical modeling to study the Chlorosomes of the green sulfur bacterium Chlorobaculum tepidum. We demonstrate that only the combination of these techniques yields unambiguous information on the structure of the bacteriochlorophyll aggregates within the Chlorosomes. Moreover, we provide a quantitative estimate of the curvature variation of these aggregates that explains ongoing debates concerning the Chlorosome structure
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Structure of Light-Harvesting Aggregates in Individual Chlorosomes B
The Journal of Physical Chemistry, 2016Co-Authors: Lisa M. Günther, Donald A Bryant, Marcus Tank, Marc Jendrny, Erik A. Bloemsma, Gert T. Oostergetel, Jasper Knoester, Jürgen KöhlerAbstract:Among all photosynthetic organisms, green bacteria have evolved one of the most efficient light-harvesting antenna, the Chlorosome, that contains hundreds of thousands of bacteriochlorophyll molecules, allowing these bacteria to grow photosynthetically by absorbing only a few photons per bacteriochlorophyll molecule per day. In contrast to other photosynthetic light-harvesting antenna systems, for which a protein scaffold imposes the proper positioning of the chromophores with respect to each other, in Chlorosomes, this is accomplished solely by self-assembly. This has aroused enormous interest in the structure–function relations of these assemblies, as they can serve as blueprints for artificial light harvesting systems. In spite of these efforts, conclusive structural information is not available yet, reflecting the sample heterogeneity inherent to the natural system. Here we combine mutagenesis, polarization-resolved single-particle fluorescence–excitation spectroscopy, cryo-electron microscopy, and theoretical modeling to study the Chlorosomes of the green sulfur bacterium Chlorobaculum tepidum. We demonstrate that only the combination of these techniques yields unambiguous information on the structure of the bacteriochlorophyll aggregates within the Chlorosomes. Moreover, we provide a quantitative estimate of the curvature variation of these aggregates that explains ongoing debates concerning the Chlorosome structure.
Mette Miller - One of the best experts on this subject based on the ideXlab platform.
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A model of the protein–pigment baseplate complex in Chlorosomes of photosynthetic green bacteria
Photosynthesis Research, 2010Co-Authors: Marie Ostergaard Pedersen, Juha Linnanto, Nielsulrik Frigaard, Niels Chr. Nielsen, Mette MillerAbstract:In contrast to photosynthetic reaction centers, which share the same structural architecture, more variety is found in the light-harvesting antenna systems of phototrophic organisms. The largest antenna system described, so far, is the Chlorosome found in anoxygenic green bacteria, as well as in a recently discovered aerobic phototroph. Chlorosomes are the only antenna system, in which the major light-harvesting pigments are organized in self-assembled supramolecular aggregates rather than on protein scaffolds. This unique feature is believed to explain why some green bacteria are able to carry out photosynthesis at very low light intensities. Encasing the Chlorosome pigments is a protein-lipid monolayer including an additional antenna complex: the baseplate, a two-dimensional paracrystalline structure containing the Chlorosome protein CsmA and bacteriochlorophyll a (BChl a). In this article, we review current knowledge of the baseplate antenna complex, which physically and functionally connects the Chlorosome pigments to the reaction centers via the Fenna–Matthews–Olson protein, with special emphasis on the well-studied green sulfur bacterium Chlorobaculum tepidum (previously Chlorobium tepidum). A possible role for the baseplate in the biogenesis of Chlorosomes is discussed. In the final part, we present a structural model of the baseplate through combination of a recent NMR structure of CsmA and simulation of circular dichroism and optical spectra for the CsmA–BChl a complex.
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a model of the protein pigment baseplate complex in Chlorosomes of photosynthetic green bacteria
Photosynthesis Research, 2010Co-Authors: Marie Ostergaard Pedersen, Juha Linnanto, Nielsulrik Frigaard, Niels Chr. Nielsen, Mette MillerAbstract:In contrast to photosynthetic reaction centers, which share the same structural architecture, more variety is found in the light-harvesting antenna systems of phototrophic organisms. The largest antenna system described, so far, is the Chlorosome found in anoxygenic green bacteria, as well as in a recently discovered aerobic phototroph. Chlorosomes are the only antenna system, in which the major light-harvesting pigments are organized in self-assembled supramolecular aggregates rather than on protein scaffolds. This unique feature is believed to explain why some green bacteria are able to carry out photosynthesis at very low light intensities. Encasing the Chlorosome pigments is a protein-lipid monolayer including an additional antenna complex: the baseplate, a two-dimensional paracrystalline structure containing the Chlorosome protein CsmA and bacteriochlorophyll a (BChl a). In this article, we review current knowledge of the baseplate antenna complex, which physically and functionally connects the Chlorosome pigments to the reaction centers via the Fenna–Matthews–Olson protein, with special emphasis on the well-studied green sulfur bacterium Chlorobaculum tepidum (previously Chlorobium tepidum). A possible role for the baseplate in the biogenesis of Chlorosomes is discussed. In the final part, we present a structural model of the baseplate through combination of a recent NMR structure of CsmA and simulation of circular dichroism and optical spectra for the CsmA–BChl a complex.
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Chlorosome lipids from chlorobium tepidum characterization and quantification of polar lipids and wax esters
Photosynthesis Research, 2008Co-Authors: Peder Grove Sorensen, Mette MillerAbstract:We have extracted polar lipids and waxes from isolated Chlorosomes from the green sulfur bacterium Chlorobium tepidum and determined the fatty acid composition of each lipid class. Polar lipids amounted to 4.8 mol per 100 mol bacteriochlorophyll in the Chlorosomes, while non-polar lipids (waxes) were present at a ratio of 5.9 mol per 100 mol bacteriochlorophyll. Glycolipids constitute 60 % of the polar lipids while phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, and an aminoglycosphingolipid make up respectively 15, 3, 8 and 12 %. A novel glycolipid was identified as a rhamnose derivative of monogalactosyldiacylglycerol, while the other major glycolipid was monogalactosyldiacylglycerol. Tetradecanoic acid was the major fatty acid in the aminoglycosphingolipid, while the other polar lipids contained predominantly hexandecanoic acid. The Chlorosome waxes are esters of unbranched fatty acids and fatty alcohols with 14 or 16 carbon atoms, joined to form molecules with between 28 and 32 carbon atoms. The stoichiometry between lipids and bacteriochlorophyll suggests that much of the Chlorosome surface is covered by protein.
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a reconstituted light harvesting complex from the green sulfur bacterium chlorobium tepidum containing csma and bacteriochlorophyll a
Biochemistry, 2008Co-Authors: Marie Ostergaard Pedersen, Lan Pham, Dorte Bjerre Steensgaard, Mette MillerAbstract:Green sulfur bacteria possess two light-harvesting antenna systems, the Chlorosome and the Fenna-Matthews-Olson (FMO) protein. In addition to self-aggregated bacteriochlorophyll (BChl) c, Chlorosomes of Chlorobium tepidum contain a small amount of BChl a (ratio 100:1). The chlorosomal BChl a is associated with CsmA, a 6.2 kDa protein that accounts for more than 50% of the protein content of Chlorosomes. This CsmA-BChl a complex is located in the Chlorosome baseplate with the hydrophilic C-terminal part of CsmA in contact with the FMO protein. CsmA was purified from Chl. tepidum. Isolated Chlorosomes were lyophilized and extracted with chloroform/methanol (1:1, v/v). The extract was further purified using gel filtration and reverse-phase HPLC and the purity of the preparation confirmed by SDS-PAGE. Mass spectrometric analysis showed an m/z of 6154.8, in agreement with the calculated mass of the csmA gene product after C-terminal processing. CD spectroscopy of the isolated protein showed that the main structural motif was an alpha-helix. We have reconstituted the isolated CsmA protein with BChl a in micelles of n-octyl beta-d-glucopyranoside. The resulting preparation reproduced the spectral characteristics of the CsmA-BChl a complex present in the Chlorosome baseplate.
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Chlorosome proteins studied by MALDI-TOF-MS: topology of CsmA in Chlorobium tepidum.
Photosynthesis research, 2005Co-Authors: Kirstin J Milks, Marianne Danielsen, Søren Persson, Ole Nørregaard Jensen, Raymond P Cox, Mette MillerAbstract:Chlorosomes, the light-harvesting apparatus of green bacteria, are a unique antenna system, in which pigments are organized in aggregates rather than associated with proteins. Isolated Chlorosomes from the green sulphur bacterium Chlorobium tepidum contain 10 surface-exposed proteins. Treatment of Chlorosomes from Chlorobium tepidum with protease caused changes in the spectral properties of bacteriochlorophyll c and digestion of Chlorosome proteins. Using SDS-PAGE analysis, immunoblotting and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) we have investigated the topology of the 59-residue CsmA protein. Our results show that at the N-terminus, the only amino acid available for protease degradation is the methionine. At the C-terminus, amino acids can be removed by protease treatment to produce a residual protein containing at least the sequence between residues 2 and 38. These results indicate that the N-terminal portion of the CsmA protein, which is predicted to be mainly hydrophobic, is buried in the Chlorosome envelope.
Nielsulrik Frigaard - One of the best experts on this subject based on the ideXlab platform.
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[2Fe-2S] proteins in Chlorosomes: CsmI and CsmJ participate in light-dependent control of energy transfer in Chlorosomes of Chlorobaculum tepidum.
Biochemistry, 2013Co-Authors: Nielsulrik Frigaard, Donald A BryantAbstract:Chlorosomes of Chlorobaculum tepidum are formed from stacks of syn–anti coordinated bacteriochlorophyll c dimers, which form a suprastructure comprised of coaxial nanotubes and are surrounded by a glycolipid monolayer envelope containing 10 proteins. Three of these proteins, CsmI, CsmJ, and CsmX, have sequences very similar in their N-terminal domains to those of [2Fe-2S] ferredoxins of the adrenodoxin/putidaredoxin subfamily. The roles of these proteins in Chlorosomes were studied in single-, double-, and triple-mutant strains. In each mutant, only the protein(s) corresponding to the mutated gene(s) was missing, and the amounts of other Chlorosome proteins did not vary significantly. Electrophoretic analyses and immunoblotting showed that CsmX was much less abundant than CsmI or CsmJ. The growth rates and the pigment and isoprenoid quinone contents of isolated Chlorosomes of the mutants were similar to wild-type values. Quenching and recovery of energy transfer in isolated Chlorosomes and intact cells we...
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[2Fe-2S] Proteins in Chlorosomes: Redox Properties of CsmI, CsmJ, and CsmX of the Chlorosome Envelope of Chlorobaculum tepidum
Biochemistry, 2013Co-Authors: T. Wade Johnson, Nielsulrik Frigaard, John H. Golbeck, Donald A BryantAbstract:The Chlorosome envelope of Chlorobaculum tepidum contains 10 polypeptides, three of which, CsmI, CsmJ, and CsmX, have an adrenodoxin-like domain harboring a single [2Fe-2S] cluster. Mutants that produced Chlorosomes containing two, one, or none of these Fe–S proteins were constructed [Li, H., et al. (2013) Biochemistry 52, preceding paper in this issue (DOI: 10.1021/bi301454g)]. The electron paramagnetic resonance (EPR) spectra, g values, and line widths of the Fe–S clusters in individual CsmI, CsmJ, and CsmX proteins were obtained from studies with isolated Chlorosomes. The Fe–S clusters in these proteins were characterized by EPR and could be differentiated on the basis of their g values and line widths. The EPR spectrum of wild-type Chlorosomes could be simulated by a 1:1 admixture of the CsmI and CsmJ spectra. No contribution of CsmX to the EPR spectrum of Chlorosomes was observed because of its low abundance. In Chlorosomes that contained only CsmI or CsmJ, the midpoint potential of the [2Fe-2S] clus...
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[2Fe-2S] Proteins in Chlorosomes: CsmI and CsmJ Participate in Light-Dependent Control of Energy Transfer in Chlorosomes of Chlorobaculum tepidum
2013Co-Authors: Nielsulrik Frigaard, Donald A BryantAbstract:Chlorosomes of Chlorobaculum tepidum are formed from stacks of syn–anti coordinated bacteriochlorophyll c dimers, which form a suprastructure comprised of coaxial nanotubes and are surrounded by a glycolipid monolayer envelope containing 10 proteins. Three of these proteins, CsmI, CsmJ, and CsmX, have sequences very similar in their N-terminal domains to those of [2Fe-2S] ferredoxins of the adrenodoxin/putidaredoxin subfamily. The roles of these proteins in Chlorosomes were studied in single-, double-, and triple-mutant strains. In each mutant, only the protein(s) corresponding to the mutated gene(s) was missing, and the amounts of other Chlorosome proteins did not vary significantly. Electrophoretic analyses and immunoblotting showed that CsmX was much less abundant than CsmI or CsmJ. The growth rates and the pigment and isoprenoid quinone contents of isolated Chlorosomes of the mutants were similar to wild-type values. Quenching and recovery of energy transfer in isolated Chlorosomes and intact cells were studied by measuring fluorescence emission after exposure to or removal of oxygen. Oxygen-induced activation of the quencher in isolated Chlorosomes or in intact cells was largely independent of CsmI and CsmJ. This may be because oxygen can diffuse across the Chlorosome envelope easily and directly reacts with the quencher. However, CsmI and CsmJ were required to restore energy transfer fully after isolated Chlorosomes were exposed to oxygen. Studies with intact cells suggested that cells contain both light-dependent and light-independent pathways for reducing the quenching species in Chlorosomes and that CsmI and CsmJ are components of a light-dependent pathway
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A model of the protein–pigment baseplate complex in Chlorosomes of photosynthetic green bacteria
Photosynthesis Research, 2010Co-Authors: Marie Ostergaard Pedersen, Juha Linnanto, Nielsulrik Frigaard, Niels Chr. Nielsen, Mette MillerAbstract:In contrast to photosynthetic reaction centers, which share the same structural architecture, more variety is found in the light-harvesting antenna systems of phototrophic organisms. The largest antenna system described, so far, is the Chlorosome found in anoxygenic green bacteria, as well as in a recently discovered aerobic phototroph. Chlorosomes are the only antenna system, in which the major light-harvesting pigments are organized in self-assembled supramolecular aggregates rather than on protein scaffolds. This unique feature is believed to explain why some green bacteria are able to carry out photosynthesis at very low light intensities. Encasing the Chlorosome pigments is a protein-lipid monolayer including an additional antenna complex: the baseplate, a two-dimensional paracrystalline structure containing the Chlorosome protein CsmA and bacteriochlorophyll a (BChl a). In this article, we review current knowledge of the baseplate antenna complex, which physically and functionally connects the Chlorosome pigments to the reaction centers via the Fenna–Matthews–Olson protein, with special emphasis on the well-studied green sulfur bacterium Chlorobaculum tepidum (previously Chlorobium tepidum). A possible role for the baseplate in the biogenesis of Chlorosomes is discussed. In the final part, we present a structural model of the baseplate through combination of a recent NMR structure of CsmA and simulation of circular dichroism and optical spectra for the CsmA–BChl a complex.
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a model of the protein pigment baseplate complex in Chlorosomes of photosynthetic green bacteria
Photosynthesis Research, 2010Co-Authors: Marie Ostergaard Pedersen, Juha Linnanto, Nielsulrik Frigaard, Niels Chr. Nielsen, Mette MillerAbstract:In contrast to photosynthetic reaction centers, which share the same structural architecture, more variety is found in the light-harvesting antenna systems of phototrophic organisms. The largest antenna system described, so far, is the Chlorosome found in anoxygenic green bacteria, as well as in a recently discovered aerobic phototroph. Chlorosomes are the only antenna system, in which the major light-harvesting pigments are organized in self-assembled supramolecular aggregates rather than on protein scaffolds. This unique feature is believed to explain why some green bacteria are able to carry out photosynthesis at very low light intensities. Encasing the Chlorosome pigments is a protein-lipid monolayer including an additional antenna complex: the baseplate, a two-dimensional paracrystalline structure containing the Chlorosome protein CsmA and bacteriochlorophyll a (BChl a). In this article, we review current knowledge of the baseplate antenna complex, which physically and functionally connects the Chlorosome pigments to the reaction centers via the Fenna–Matthews–Olson protein, with special emphasis on the well-studied green sulfur bacterium Chlorobaculum tepidum (previously Chlorobium tepidum). A possible role for the baseplate in the biogenesis of Chlorosomes is discussed. In the final part, we present a structural model of the baseplate through combination of a recent NMR structure of CsmA and simulation of circular dichroism and optical spectra for the CsmA–BChl a complex.
Hitoshi Tamiaki - One of the best experts on this subject based on the ideXlab platform.
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supramolecular chlorophyll aggregates inspired from specific light harvesting antenna Chlorosome static nanostructure dynamic construction process and versatile application
Journal of Photochemistry and Photobiology C-photochemistry Reviews, 2020Co-Authors: Shogo Matsubara, Hitoshi TamiakiAbstract:Abstract Photosynthetic light-harvesting antennas possess a variety of supramolecular structures with the same function (collecting sunlight energy), dependent on their living habitats and environments of phototrophs. Notably, the main antenna in green photosynthetic bacteria called “Chlorosome” is structurally unique. Its core is constructed solely from self-aggregates of chlorophyll molecules without the support of any protein scaffolds. The supramolecular structures of the chlorophyll aggregates were already estimated, but have not been determined completely due to the natural diversity of Chlorosomes. The static structures of Chlorosomes are somewhat difficult to be characterized, and also the determination of their dynamic construction processes in vivo, such as their biogenesis and growth, is more challenging. Consequently, the measurement and observation of a simplified Chlorosome model prepared by in vitro self-assembly of native or non-native (semisynthetic) chlorophylls are important. The present review focuses on evaluation of the static and dynamic nanostructures of chlorosomal aggregates. The construction, observation, and analysis of such models could be translated into the supramolecular aggregates of native Chlorosomes. Additionally, synthetic aggregates display remarkable properties, which would be valuable for the development of solar cells and artificial photosynthesis. Such systems could potentially also be applied as photofunctional materials.
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Glycolipid analyses of light-harvesting Chlorosomes from envelope protein mutants of Chlorobaculum tepidum
Photosynthesis Research, 2016Co-Authors: Yusuke Tsukatani, Donald A Bryant, Tadashi Mizoguchi, Jennifer Thweatt, Marcus Tank, Hitoshi TamiakiAbstract:Chlorosomes are large and efficient light-harvesting organelles in green photosynthetic bacteria, and they characteristically contain large numbers of bacteriochlorophyll c, d, or e molecules. Self-aggregated bacteriochlorophyll pigments are surrounded by a monolayer envelope membrane comprised of glycolipids and Csm proteins. Here, we analyzed glycolipid compositions of Chlorosomes from the green sulfur bacterium Chlorobaculum tepidum mutants lacking one, two, or three Csm proteins by HPLC equipped with an evaporative light-scattering detector. The ratio of monogalactosyldiacylglyceride (MGDG) to rhamnosylgalactosyldiacylglyceride (RGDG) was smaller in Chlorosomes from mutants lacking two or three proteins in CsmC/D/H motif family than in Chlorosomes from the wild-type, whereas Chlorosomes lacking CsmIJ showed relatively less RGDG than MGDG. The results suggest that the CsmC, CsmD, CsmH, and other Chlorosome proteins are involved in organizing MGDG and RGDG and thereby affect the size and shape of the Chlorosome.
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Cyclopropane-ring formation in the acyl groups of Chlorosome glycolipids is crucial for acid resistance of green bacterial antenna systems.
Bioorganic & medicinal chemistry, 2013Co-Authors: Tadashi Mizoguchi, Yusuke Tsukatani, Jiro Harada, Shin Takasaki, Taichi Yoshitomi, Hitoshi TamiakiAbstract:Abstract Green photosynthetic bacteria have unique light-harvesting antenna systems called Chlorosomes. Chlorobaculum tepidum , a model organism of the bacteria, biosynthesized monogalactosyl- and rhamnosylgalactosyldiacylglycerides possessing a methylene-bridged palmitoleyl group characterized by a cis -substituted cyclopropane ring as the dominant glycolipids of its Chlorosome surface. The formation of the cyclopropane ring was chemically inhibited by supplementation of sinefungin, an analog of S -adenosyl- l -methionine, into the bacterial cultivation. The presence of the cyclopropane ring reinforced acid resistance of the light-harvesting Chlorosomes and suppressed acidic demetalation (pheophytinization) of bacteriochlorophyll- c pigments constructing the core part of Chlorosomes. The ring-formation would represent direct and post-synthetic modifications of Chlorosome membrane properties and was tolerant of acidic environments.
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Anisotropic distribution of emitting transition dipoles in Chlorosome from Chlorobium tepidum: fluorescence polarization anisotropy study of single Chlorosomes
Photosynthesis Research, 2009Co-Authors: Yutaka Shibata, Hitoshi Tamiaki, Yoshitaka Saga, Shigeru ItohAbstract:The polarization anisotropy of fluorescence spectra from single Chlorosomes isolated from a green sulfur bacterium, Chlorobium ( Cb .) tepidum , was observed at 13 K. As the polarizer was rotated, the intensities of the fluorescence bands of both bacteriochlorophyll (BChl)- c self-aggregates and BChl- a in baseplate proteins showed clear oscillations. From the oscillation, the values of the degree of polarization (DP) and the phase shift (PS) between the BChl- c and BChl- a bands were determined for each single Chlorosome. The DP versus PS plot for Cb . tepidum Chlorosomes showed linear correlations between the PS and the DP values for both BChl- c and BChl- a fluorescence bands. This tendency could be explained from a simulation assuming a random orientation of Chlorosomes and a triaxial orientation distribution of emitting transition dipoles within a single Chlorosome. The intensity ratios among the X -/ Y -/ Z -principal transition dipoles were estimated to be 0.3/0.5/1 and 1/0.6/0.1 for the BChl- c and BChl- a fluorescence bands, respectively. Here, the X -, Y -, and Z -axes are perpendicular, parallel to the cytoplasmic membrane, and parallel to the Chlorosome long axis, respectively. A theoretical calculation based on the exciton theory was conducted to reproduce the observed triaxial orientation distribution of emitting transition dipoles. The simulation revealed that a deformation introduced to the circular cross section of the rod-shaped BChl- c self-aggregates could qualitatively reproduce results of this study.
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Polarized fluorescence of aggregated bacteriochlorophyll c and baseplate bacteriochlorophyll a in single Chlorosomes isolated from Chloroflexus aurantiacus.
Biochemistry, 2007Co-Authors: Yutaka Shibata, Hitoshi Tamiaki, Yoshitaka Saga, Shigeru ItohAbstract:The polarization anisotropy of fluorescence from single Chlorosomes isolated from a green filamentous bacterium, Chloroflexus aurantiacus, was measured using a confocal laser microscope at 13 K. Each single Chlorosome that is floating in a frozen solvent exhibited strong polarization anisotropy of fluorescence. We calculated the degrees of fluorescence polarization for 51 floating single Chlorosomes. The value ranged from 0.1 to 0.76 for the BChl-c aggregate in the core Chlorosomes and from 0 to 0.4 for the energy acceptor BChl-a in the baseplate protein in the outer membrane. The shifts in polarization angles between the two emission bands were distributed over all the possible values with a sharp peak around 90°, suggesting the perpendicular orientation between the transition dipoles of the fluorescence emission from the BChl-c aggregate and that from BChl-a. A simulation assuming a random orientation of Chlorosomes reproduced the experimental results exactly. The analysis further indicated the apprecia...