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Samuel M Luedin - One of the best experts on this subject based on the ideXlab platform.
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Data_Sheet_1_Mixotrophic Growth Under Micro-Oxic Conditions in the Purple Sulfur Bacterium “Thiodictyon syntrophicum”.pdf
2019Co-Authors: Samuel M Luedin, Nicola Storelli, Joel F Pothier, Matthias Wittwer, Francesco Danza, Samuele Roman, Mauro TonollaAbstract:The microbial ecosystem of the meromictic Lake Cadagno (Ticino, Swiss Alps) has been studied intensively in order to understand structure and functioning of the anoxygenic phototrophic Sulfur bacteria community living in the chemocline. It has been found that the purple Sulfur Bacterium “Thiodictyon syntrophicum” strain Cad16T, belonging to the Chromatiaceae, fixes around 26% of all bulk inorganic carbon in the chemocline, both during day and night. With this study, we elucidated for the first time the mode of carbon fixation of str. Cad16T under micro-oxic conditions with a combination of long-term monitoring of key physicochemical parameters with CTD, 14C-incorporation experiments and quantitative proteomics using in-situ dialysis bag incubations of str. Cad16T cultures. Regular vertical CTD profiling during the study period in summer 2017 revealed that the chemocline sank from 12 to 14 m which was accompanied by a bloom of cyanobacteria and the subsequent oxygenation of the deeper water column. Sampling was performed both day and night. CO2 assimilation rates were higher during the light period compared to those in the dark, both in the chemocline population and in the incubated cultures. The relative change in the proteome between day and night (663 quantified proteins) comprised only 1% of all proteins encoded in str. Cad16T. Oxidative respiration pathways were upregulated at light, whereas stress-related mechanisms prevailed during the night. These results indicate that low light availability and the co-occurring oxygenation of the chemocline induced mixotrophic growth in str. Cad16T. Our study thereby helps to further understand the consequences micro-oxic conditions for phototrophic Sulfur oxidizing bacteria. The complete proteome data have been deposited to the ProteomeXchange database with identifier PXD010641.
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complete genome sequence of thiodictyon syntrophicum sp nov strain cad16t a photolithoautotrophic purple Sulfur Bacterium isolated from the alpine meromictic lake cadagno
Standards in Genomic Sciences, 2018Co-Authors: Nicola Storelli, Samuel M Luedin, Joel F Pothier, Nielsulrik Frigaard, Matthias WittwerAbstract:“Thiodictyon syntrophicum” sp. nov. strain Cad16T is a photoautotrophic purple Sulfur Bacterium belonging to the family of Chromatiaceae in the class of Gammaproteobacteria. The type strain Cad16T was isolated from the chemocline of the alpine meromictic Lake Cadagno in Switzerland. Strain Cad16T represents a key species within this Sulfur-driven bacterial ecosystem with respect to carbon fixation. The 7.74-Mbp genome of strain Cad16T has been sequenced and annotated. It encodes 6237 predicted protein sequences and 59 RNA sequences. Phylogenetic comparison based on 16S rRNA revealed that Thiodictyon elegans strain DSM 232T the most closely related species. Genes involved in Sulfur oxidation, central carbon metabolism and transmembrane transport were found. Noteworthy, clusters of genes encoding the photosynthetic machinery and pigment biosynthesis are found on the 0.48 Mb plasmid pTs485. We provide a detailed insight into the Cad16T genome and analyze it in the context of the microbial ecosystem of Lake Cadagno.
Tsunenori Nozawa - One of the best experts on this subject based on the ideXlab platform.
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structure of the h subunit of the photosynthetic reaction center from the thermophilic purple Sulfur Bacterium thermochromatium tepidum implications for the specific binding of the lipid molecule to the membrane protein complex
FEBS Journal, 2001Co-Authors: Masayuki Kobayashi, Insan Fathir, Takayuki Mori, Terukazu Nogi, Kunio Miki, Tsunenori NozawaAbstract:The photosynthetic reaction center (RC) is a transmembrane protein complex that catalyzes light-driven electron transport across the photosynthetic membrane. The complete amino-acid sequence of the H subunit of the RC from a thermophilic purple Sulfur Bacterium, Thermochromatium tepidum, has been determined for the first time among purple Sulfur bacteria. The H subunit consists of 259 amino acids and has a molecular mass of 28 187. The deduced amino-acid sequences of this H subunit showed a significant (40%) degree of identity with those from mesophilic purple nonSulfur bacteria. The determined primary structure of the H subunit was compared with the structures of mesophilic B. viridis and R. sphaeroides based on the three-dimensional structure of the H subunit from T. tepidum, which has been recently determined by X-ray crystallography. One lipid molecule was found in the crystal structure of the T. tepidum RC, and the head group of the lipid appears to be stabilized by the electrostatic interactions with the conserved basic residues in the H subunit. The above comparison has suggested the existence of a lipid-binding site on the molecular surface at which a lipid molecule can interact with the RC in a specific manner.
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biochemical and spectral characterization of the core light harvesting complex 1 lh1 from the thermophilic purple Sulfur Bacterium chromatium tepidum
Photosynthesis Research, 1998Co-Authors: Insan Fathir, Masayuki Kobayashi, Zhengyu Wang, Mitsuhiro Ashikaga, Kohki Tanaka, Takashi Katano, Takashi Nirasawa, Tsunenori NozawaAbstract:The photoreceptor complex (LH1-RC) of the thermophilic purple Sulfur Bacterium Chromatium tepidum (Chr. tepidum) has been investigated and isolated using the detergent Triton X-100 followed by sucrose density gradient centrifugation (SDGC). The isolated LH1-RC complex had an absorption maximum at 915 nm, the longest absorption band observed in light harvesting complex 1 (LH1) in purple bacteria containing bacteriochlorophyll a (BChl a). The absorption maximum of this LH1-RC complex showed a 30 nm blue-shift to 885 nm after being purified by DEAE cellulose column chromatography. The blue-shifted absorption band was found to return to 915 nm after removing the salt ion, indicating a reversible effect of salt ion on this LH1-RC complex. We have determined the nucleotide sequences of genes coding for the α, β polypeptide subunits of the LH1 core complex from Chr. tepidum and have found some characteristic features. The deduced amino acid sequences of the α subunit showed a deletion of an arginine residue in the C terminal of membrane helix. A possible correlation between the unusual absorption behavior and structural features of α and β polypeptide subunits of the LH1 core complex is discussed.
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new carotenoids from the thermophilic green Sulfur Bacterium chlorobium tepidum 1 2 dihydro γ carotene 1 2 dihydrochlorobactene and oh chlorobactene glucoside ester and the carotenoid composition of different strains
Archives of Microbiology, 1997Co-Authors: Shinichi Takaichi, Zhengyu Wang, Tsunenori Nozawa, Mitsuo Umetsu, Keizo Shimada, Michael T MadiganAbstract:The complete carotenoid composition of the thermophilic green Sulfur Bacterium Chlorobium tepidum strain TNO was determined by spectroscopic methods. Major carotenoids were four kinds of carotenes: γ-carotene, chlorobactene, and their 1′,2′-dihydro derivatives (1′,2′-dihydro-γ-carotene and 1′,2′-dihydrochlorobactene). In lesser amounts, hydroxyl γ-carotene, hydroxyl chlorobactene, and their glucoside fatty acid esters were found. The only esterified fatty acid present was laurate, and OH-chlorobactene glucoside laurate is a novel carotenoid. In other strains of C. tepidum, the same carotenoids were found, but the composition varied from strain to strain. The overall pigment composition in cells of strain TNO was 4 mol carotenoids and 40 mol bacteriochlorophyll c per mol bacteriochlorophyll a. The effects of nicotine on carotenoid biosynthesis in C. tepidum differed from those in the thermophilic green nonSulfur Bacterium Chloroflexus aurantiacus.
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The genes coding for the L, M and cytochrome subunits of the photosynthetic reaction center from the thermophilic purple Sulfur Bacterium t Chromatium tepidum
Photosynthesis Research, 1997Co-Authors: Insan Fathir, Masayuki Kobayashi, Zhengyu Wang, Kohki Tanaka, Kenji Yoza, Akihiko Kojima, Friedrich Lottspeich, Tsunenori NozawaAbstract:The complete nucleotide sequences of the genes coding for L, M protein subunits and part of cytochrome subunit of the photosynthetic reaction center were determined for the thermophilic purple Sulfur Bacterium t Chromatium tepidum (t Chr. tepidum) which belongs to the γ subclass. The DNA fragments with 860 bp and 1900 bp were amplified by the Polymerase Chain Reaction (PCR) with the primers designed on the basis of amino acid sequences according to chemical sequence analysis of the proteins. The deduced amino acid sequences of these genes showed a significantly high degree of homology with those from purple non-Sulfur bacteria. The L subunit consisted of 280 amino acids and had a molecular mass of 31,393. The M subunit consisted of 324 amino acids and had a molecular mass of 36,299. The aligned sequences of the L subunits of other purple bacterial reaction center polypeptides, showed the insertion of 8 amino acids in t Chr. tepidum in the connection of the first and second membrane-spanning helices different from those of purple non-Sulfur bacteria. The aligned sequences of the L, M and cytochrome subunits were compared with other species and discussed in terms of phylogenetic trees.
Zhengyu Wang - One of the best experts on this subject based on the ideXlab platform.
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calcium ions are involved in the unusual red shift of the light harvesting 1 qy transition of the core complex in thermophilic purple Sulfur Bacterium thermochromatium tepidum
Journal of Biological Chemistry, 2008Co-Authors: Yukihiro Kimura, Yu Hirano, Hiroaki Suzuki, Masayuki Kobayashi, Zhengyu WangAbstract:Thermophilic purple Sulfur Bacterium, Thermochromatium tepidum, can grow at temperatures up to 58 degrees C and exhibits an unusual Qy absorption at 915 nm for the core light-harvesting complex (LH1), an approximately 35-nm red shift from those of its mesophilic counterparts. We demonstrate in this study, using a highly purified LH1-reaction center complex, that the LH1 Qy transition is strongly dependent on metal cations and Ca2+ is involved in the unusual red shift. Removal of the Ca2+ resulted in formation of a species with the LH1 Qy absorption at 880 nm, and addition of the Ca2+ to the 880-nm species recovered the native 915-nm form. Interchange between the two forms is fully reversible. Based on spectroscopic and isothermal titration calorimetry analyses, the Ca2+ binding to the LH1 complex was estimated to occur in a stoichiometric ratio of Ca2+/alphabeta-subunit = 1:1 and the binding constant was in 10(5) m(-1) order of magnitude, which is comparable with those for EF-hand Ca2+-binding proteins. Despite the high affinity, conformational changes in the LH1 complex upon Ca2+ binding were small and occurred slowly, with a typical time constant of approximately 6 min. Replacement of the Ca2+ with other metal cations caused blue shifts of the Qy bands depending on the property of the cations, indicating that the binding site is highly selective. Based on the amino acid sequences of the LH1 complex, possible Ca2+-binding sites are proposed that consist of several acidic amino acid residues near the membrane interfaces of the C-terminal region of the alpha-polypeptide and the N-terminal region of the beta-polypeptide.
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purification characterization and crystallization of the core complex from thermophilic purple Sulfur Bacterium thermochromatium tepidum
Biochimica et Biophysica Acta, 2007Co-Authors: Hiroaki Suzuki, Yukihiro Kimura, Yu Hirano, Masayuki Kobayashi, Kunio Miki, Shinichi Takaichi, Zhengyu WangAbstract:A light-harvesting-reaction center (LH1-RC) core complex has been highly purified from a thermophilic purple Sulfur Bacterium, Thermochromatium tepidum. The bacteriochlorophyll (BChl) a molecules in the LH1 exhibit a Q(y) transition at 914 nm, more than 25 nm red-shift from those of its mesophilic counterparts. The LH1-RC complex was isolated in a monomeric form as confirmed by sucrose density gradient centrifugation, blue native PAGE and size-exclusion chromatography. Four subunits (L, M, H and a tetraheme cytochrome) in RC and two polypeptides (alpha and beta) in LH1 were identified. Spirilloxanthin was determined to be the predominant carotenoid in the core complex. The purified core complex was highly stable, no significant change in the LH1 Q(y) transition was observed over 10 days of incubation at room temperature in dark. Circular dichroism spectrum of the LH1 complex was characterized by low intensity and nonconservative spectral shape, implying a high symmetry of the large LH1 ring and interaction between the BChl a and carotenoid molecules. A dimeric feature of the BChl a molecules in LH1 was revealed by magnetic circular dichroism spectrum. Crystals of the core complex were obtained which diffracted X-rays to about 10 A.
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biochemical and spectral characterization of the core light harvesting complex 1 lh1 from the thermophilic purple Sulfur Bacterium chromatium tepidum
Photosynthesis Research, 1998Co-Authors: Insan Fathir, Masayuki Kobayashi, Zhengyu Wang, Mitsuhiro Ashikaga, Kohki Tanaka, Takashi Katano, Takashi Nirasawa, Tsunenori NozawaAbstract:The photoreceptor complex (LH1-RC) of the thermophilic purple Sulfur Bacterium Chromatium tepidum (Chr. tepidum) has been investigated and isolated using the detergent Triton X-100 followed by sucrose density gradient centrifugation (SDGC). The isolated LH1-RC complex had an absorption maximum at 915 nm, the longest absorption band observed in light harvesting complex 1 (LH1) in purple bacteria containing bacteriochlorophyll a (BChl a). The absorption maximum of this LH1-RC complex showed a 30 nm blue-shift to 885 nm after being purified by DEAE cellulose column chromatography. The blue-shifted absorption band was found to return to 915 nm after removing the salt ion, indicating a reversible effect of salt ion on this LH1-RC complex. We have determined the nucleotide sequences of genes coding for the α, β polypeptide subunits of the LH1 core complex from Chr. tepidum and have found some characteristic features. The deduced amino acid sequences of the α subunit showed a deletion of an arginine residue in the C terminal of membrane helix. A possible correlation between the unusual absorption behavior and structural features of α and β polypeptide subunits of the LH1 core complex is discussed.
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new carotenoids from the thermophilic green Sulfur Bacterium chlorobium tepidum 1 2 dihydro γ carotene 1 2 dihydrochlorobactene and oh chlorobactene glucoside ester and the carotenoid composition of different strains
Archives of Microbiology, 1997Co-Authors: Shinichi Takaichi, Zhengyu Wang, Tsunenori Nozawa, Mitsuo Umetsu, Keizo Shimada, Michael T MadiganAbstract:The complete carotenoid composition of the thermophilic green Sulfur Bacterium Chlorobium tepidum strain TNO was determined by spectroscopic methods. Major carotenoids were four kinds of carotenes: γ-carotene, chlorobactene, and their 1′,2′-dihydro derivatives (1′,2′-dihydro-γ-carotene and 1′,2′-dihydrochlorobactene). In lesser amounts, hydroxyl γ-carotene, hydroxyl chlorobactene, and their glucoside fatty acid esters were found. The only esterified fatty acid present was laurate, and OH-chlorobactene glucoside laurate is a novel carotenoid. In other strains of C. tepidum, the same carotenoids were found, but the composition varied from strain to strain. The overall pigment composition in cells of strain TNO was 4 mol carotenoids and 40 mol bacteriochlorophyll c per mol bacteriochlorophyll a. The effects of nicotine on carotenoid biosynthesis in C. tepidum differed from those in the thermophilic green nonSulfur Bacterium Chloroflexus aurantiacus.
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The genes coding for the L, M and cytochrome subunits of the photosynthetic reaction center from the thermophilic purple Sulfur Bacterium t Chromatium tepidum
Photosynthesis Research, 1997Co-Authors: Insan Fathir, Masayuki Kobayashi, Zhengyu Wang, Kohki Tanaka, Kenji Yoza, Akihiko Kojima, Friedrich Lottspeich, Tsunenori NozawaAbstract:The complete nucleotide sequences of the genes coding for L, M protein subunits and part of cytochrome subunit of the photosynthetic reaction center were determined for the thermophilic purple Sulfur Bacterium t Chromatium tepidum (t Chr. tepidum) which belongs to the γ subclass. The DNA fragments with 860 bp and 1900 bp were amplified by the Polymerase Chain Reaction (PCR) with the primers designed on the basis of amino acid sequences according to chemical sequence analysis of the proteins. The deduced amino acid sequences of these genes showed a significantly high degree of homology with those from purple non-Sulfur bacteria. The L subunit consisted of 280 amino acids and had a molecular mass of 31,393. The M subunit consisted of 324 amino acids and had a molecular mass of 36,299. The aligned sequences of the L subunits of other purple bacterial reaction center polypeptides, showed the insertion of 8 amino acids in t Chr. tepidum in the connection of the first and second membrane-spanning helices different from those of purple non-Sulfur bacteria. The aligned sequences of the L, M and cytochrome subunits were compared with other species and discussed in terms of phylogenetic trees.
Insan Fathir - One of the best experts on this subject based on the ideXlab platform.
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structure of the h subunit of the photosynthetic reaction center from the thermophilic purple Sulfur Bacterium thermochromatium tepidum implications for the specific binding of the lipid molecule to the membrane protein complex
FEBS Journal, 2001Co-Authors: Masayuki Kobayashi, Insan Fathir, Takayuki Mori, Terukazu Nogi, Kunio Miki, Tsunenori NozawaAbstract:The photosynthetic reaction center (RC) is a transmembrane protein complex that catalyzes light-driven electron transport across the photosynthetic membrane. The complete amino-acid sequence of the H subunit of the RC from a thermophilic purple Sulfur Bacterium, Thermochromatium tepidum, has been determined for the first time among purple Sulfur bacteria. The H subunit consists of 259 amino acids and has a molecular mass of 28 187. The deduced amino-acid sequences of this H subunit showed a significant (40%) degree of identity with those from mesophilic purple nonSulfur bacteria. The determined primary structure of the H subunit was compared with the structures of mesophilic B. viridis and R. sphaeroides based on the three-dimensional structure of the H subunit from T. tepidum, which has been recently determined by X-ray crystallography. One lipid molecule was found in the crystal structure of the T. tepidum RC, and the head group of the lipid appears to be stabilized by the electrostatic interactions with the conserved basic residues in the H subunit. The above comparison has suggested the existence of a lipid-binding site on the molecular surface at which a lipid molecule can interact with the RC in a specific manner.
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biochemical and spectral characterization of the core light harvesting complex 1 lh1 from the thermophilic purple Sulfur Bacterium chromatium tepidum
Photosynthesis Research, 1998Co-Authors: Insan Fathir, Masayuki Kobayashi, Zhengyu Wang, Mitsuhiro Ashikaga, Kohki Tanaka, Takashi Katano, Takashi Nirasawa, Tsunenori NozawaAbstract:The photoreceptor complex (LH1-RC) of the thermophilic purple Sulfur Bacterium Chromatium tepidum (Chr. tepidum) has been investigated and isolated using the detergent Triton X-100 followed by sucrose density gradient centrifugation (SDGC). The isolated LH1-RC complex had an absorption maximum at 915 nm, the longest absorption band observed in light harvesting complex 1 (LH1) in purple bacteria containing bacteriochlorophyll a (BChl a). The absorption maximum of this LH1-RC complex showed a 30 nm blue-shift to 885 nm after being purified by DEAE cellulose column chromatography. The blue-shifted absorption band was found to return to 915 nm after removing the salt ion, indicating a reversible effect of salt ion on this LH1-RC complex. We have determined the nucleotide sequences of genes coding for the α, β polypeptide subunits of the LH1 core complex from Chr. tepidum and have found some characteristic features. The deduced amino acid sequences of the α subunit showed a deletion of an arginine residue in the C terminal of membrane helix. A possible correlation between the unusual absorption behavior and structural features of α and β polypeptide subunits of the LH1 core complex is discussed.
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The genes coding for the L, M and cytochrome subunits of the photosynthetic reaction center from the thermophilic purple Sulfur Bacterium t Chromatium tepidum
Photosynthesis Research, 1997Co-Authors: Insan Fathir, Masayuki Kobayashi, Zhengyu Wang, Kohki Tanaka, Kenji Yoza, Akihiko Kojima, Friedrich Lottspeich, Tsunenori NozawaAbstract:The complete nucleotide sequences of the genes coding for L, M protein subunits and part of cytochrome subunit of the photosynthetic reaction center were determined for the thermophilic purple Sulfur Bacterium t Chromatium tepidum (t Chr. tepidum) which belongs to the γ subclass. The DNA fragments with 860 bp and 1900 bp were amplified by the Polymerase Chain Reaction (PCR) with the primers designed on the basis of amino acid sequences according to chemical sequence analysis of the proteins. The deduced amino acid sequences of these genes showed a significantly high degree of homology with those from purple non-Sulfur bacteria. The L subunit consisted of 280 amino acids and had a molecular mass of 31,393. The M subunit consisted of 324 amino acids and had a molecular mass of 36,299. The aligned sequences of the L subunits of other purple bacterial reaction center polypeptides, showed the insertion of 8 amino acids in t Chr. tepidum in the connection of the first and second membrane-spanning helices different from those of purple non-Sulfur bacteria. The aligned sequences of the L, M and cytochrome subunits were compared with other species and discussed in terms of phylogenetic trees.
Masayuki Kobayashi - One of the best experts on this subject based on the ideXlab platform.
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calcium ions are involved in the unusual red shift of the light harvesting 1 qy transition of the core complex in thermophilic purple Sulfur Bacterium thermochromatium tepidum
Journal of Biological Chemistry, 2008Co-Authors: Yukihiro Kimura, Yu Hirano, Hiroaki Suzuki, Masayuki Kobayashi, Zhengyu WangAbstract:Thermophilic purple Sulfur Bacterium, Thermochromatium tepidum, can grow at temperatures up to 58 degrees C and exhibits an unusual Qy absorption at 915 nm for the core light-harvesting complex (LH1), an approximately 35-nm red shift from those of its mesophilic counterparts. We demonstrate in this study, using a highly purified LH1-reaction center complex, that the LH1 Qy transition is strongly dependent on metal cations and Ca2+ is involved in the unusual red shift. Removal of the Ca2+ resulted in formation of a species with the LH1 Qy absorption at 880 nm, and addition of the Ca2+ to the 880-nm species recovered the native 915-nm form. Interchange between the two forms is fully reversible. Based on spectroscopic and isothermal titration calorimetry analyses, the Ca2+ binding to the LH1 complex was estimated to occur in a stoichiometric ratio of Ca2+/alphabeta-subunit = 1:1 and the binding constant was in 10(5) m(-1) order of magnitude, which is comparable with those for EF-hand Ca2+-binding proteins. Despite the high affinity, conformational changes in the LH1 complex upon Ca2+ binding were small and occurred slowly, with a typical time constant of approximately 6 min. Replacement of the Ca2+ with other metal cations caused blue shifts of the Qy bands depending on the property of the cations, indicating that the binding site is highly selective. Based on the amino acid sequences of the LH1 complex, possible Ca2+-binding sites are proposed that consist of several acidic amino acid residues near the membrane interfaces of the C-terminal region of the alpha-polypeptide and the N-terminal region of the beta-polypeptide.
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purification characterization and crystallization of the core complex from thermophilic purple Sulfur Bacterium thermochromatium tepidum
Biochimica et Biophysica Acta, 2007Co-Authors: Hiroaki Suzuki, Yukihiro Kimura, Yu Hirano, Masayuki Kobayashi, Kunio Miki, Shinichi Takaichi, Zhengyu WangAbstract:A light-harvesting-reaction center (LH1-RC) core complex has been highly purified from a thermophilic purple Sulfur Bacterium, Thermochromatium tepidum. The bacteriochlorophyll (BChl) a molecules in the LH1 exhibit a Q(y) transition at 914 nm, more than 25 nm red-shift from those of its mesophilic counterparts. The LH1-RC complex was isolated in a monomeric form as confirmed by sucrose density gradient centrifugation, blue native PAGE and size-exclusion chromatography. Four subunits (L, M, H and a tetraheme cytochrome) in RC and two polypeptides (alpha and beta) in LH1 were identified. Spirilloxanthin was determined to be the predominant carotenoid in the core complex. The purified core complex was highly stable, no significant change in the LH1 Q(y) transition was observed over 10 days of incubation at room temperature in dark. Circular dichroism spectrum of the LH1 complex was characterized by low intensity and nonconservative spectral shape, implying a high symmetry of the large LH1 ring and interaction between the BChl a and carotenoid molecules. A dimeric feature of the BChl a molecules in LH1 was revealed by magnetic circular dichroism spectrum. Crystals of the core complex were obtained which diffracted X-rays to about 10 A.
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structure of the h subunit of the photosynthetic reaction center from the thermophilic purple Sulfur Bacterium thermochromatium tepidum implications for the specific binding of the lipid molecule to the membrane protein complex
FEBS Journal, 2001Co-Authors: Masayuki Kobayashi, Insan Fathir, Takayuki Mori, Terukazu Nogi, Kunio Miki, Tsunenori NozawaAbstract:The photosynthetic reaction center (RC) is a transmembrane protein complex that catalyzes light-driven electron transport across the photosynthetic membrane. The complete amino-acid sequence of the H subunit of the RC from a thermophilic purple Sulfur Bacterium, Thermochromatium tepidum, has been determined for the first time among purple Sulfur bacteria. The H subunit consists of 259 amino acids and has a molecular mass of 28 187. The deduced amino-acid sequences of this H subunit showed a significant (40%) degree of identity with those from mesophilic purple nonSulfur bacteria. The determined primary structure of the H subunit was compared with the structures of mesophilic B. viridis and R. sphaeroides based on the three-dimensional structure of the H subunit from T. tepidum, which has been recently determined by X-ray crystallography. One lipid molecule was found in the crystal structure of the T. tepidum RC, and the head group of the lipid appears to be stabilized by the electrostatic interactions with the conserved basic residues in the H subunit. The above comparison has suggested the existence of a lipid-binding site on the molecular surface at which a lipid molecule can interact with the RC in a specific manner.
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biochemical and spectral characterization of the core light harvesting complex 1 lh1 from the thermophilic purple Sulfur Bacterium chromatium tepidum
Photosynthesis Research, 1998Co-Authors: Insan Fathir, Masayuki Kobayashi, Zhengyu Wang, Mitsuhiro Ashikaga, Kohki Tanaka, Takashi Katano, Takashi Nirasawa, Tsunenori NozawaAbstract:The photoreceptor complex (LH1-RC) of the thermophilic purple Sulfur Bacterium Chromatium tepidum (Chr. tepidum) has been investigated and isolated using the detergent Triton X-100 followed by sucrose density gradient centrifugation (SDGC). The isolated LH1-RC complex had an absorption maximum at 915 nm, the longest absorption band observed in light harvesting complex 1 (LH1) in purple bacteria containing bacteriochlorophyll a (BChl a). The absorption maximum of this LH1-RC complex showed a 30 nm blue-shift to 885 nm after being purified by DEAE cellulose column chromatography. The blue-shifted absorption band was found to return to 915 nm after removing the salt ion, indicating a reversible effect of salt ion on this LH1-RC complex. We have determined the nucleotide sequences of genes coding for the α, β polypeptide subunits of the LH1 core complex from Chr. tepidum and have found some characteristic features. The deduced amino acid sequences of the α subunit showed a deletion of an arginine residue in the C terminal of membrane helix. A possible correlation between the unusual absorption behavior and structural features of α and β polypeptide subunits of the LH1 core complex is discussed.
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The genes coding for the L, M and cytochrome subunits of the photosynthetic reaction center from the thermophilic purple Sulfur Bacterium t Chromatium tepidum
Photosynthesis Research, 1997Co-Authors: Insan Fathir, Masayuki Kobayashi, Zhengyu Wang, Kohki Tanaka, Kenji Yoza, Akihiko Kojima, Friedrich Lottspeich, Tsunenori NozawaAbstract:The complete nucleotide sequences of the genes coding for L, M protein subunits and part of cytochrome subunit of the photosynthetic reaction center were determined for the thermophilic purple Sulfur Bacterium t Chromatium tepidum (t Chr. tepidum) which belongs to the γ subclass. The DNA fragments with 860 bp and 1900 bp were amplified by the Polymerase Chain Reaction (PCR) with the primers designed on the basis of amino acid sequences according to chemical sequence analysis of the proteins. The deduced amino acid sequences of these genes showed a significantly high degree of homology with those from purple non-Sulfur bacteria. The L subunit consisted of 280 amino acids and had a molecular mass of 31,393. The M subunit consisted of 324 amino acids and had a molecular mass of 36,299. The aligned sequences of the L subunits of other purple bacterial reaction center polypeptides, showed the insertion of 8 amino acids in t Chr. tepidum in the connection of the first and second membrane-spanning helices different from those of purple non-Sulfur bacteria. The aligned sequences of the L, M and cytochrome subunits were compared with other species and discussed in terms of phylogenetic trees.
