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Michael T. Madigan - One of the best experts on this subject based on the ideXlab platform.
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Dimer Structures of Bacteriochlorophyll c from Chlorobium tepidum in CDCl3
Chemistry Letters, 1992Co-Authors: Tsunenori Nozawa, Katsunori Ohtomo, Yumi Morishita, Hideo Konami, Michael T. MadiganAbstract:As an aggregate structure in CDCl3 a piggyback type dimer was suggested for bacteriochlorophyll (BChl) c from Chlorobium tepidum on the basis of variations of 1H NMR chemical shifts accompanied with the aggregate formation and of values of calculated ring current shifts.
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Substituent effects on the aggregation of bacteriochlorophyll d homologues purified from Chlorobium limicola
Bulletin of the Chemical Society of Japan, 1992Co-Authors: Tsunenori Nozawa, Katsunori Ohtomo, Yumi Morishita, Naohiro Takeshita, Masatoshi Osawa, Michael T. MadiganAbstract:Six bacteriochlorophyll (BChl) d homologues were isolated from Chlorobium limicola. The absorption spectral profiles in hexane–dichloromethane and the solvent effects indicate that the aggregation property of the BChl d’s strongly depend on the nature of the peripheral substituents.
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A thermophilic green sulfur bacterium from New Zealand hot springs, Chlorobium tepidum sp. nov.
Archives of Microbiology, 1991Co-Authors: Thomas M. Wahlund, Carl R. Woese, Richard W. Castenholz, Michael T. MadiganAbstract:Thermophilic green sulfur bacteria of the genus Chlorobium were isolated from certain acidic high sulfide New Zealand hot springs. Cells were Gram-negative nonmotile rods of variable length and contained bacteriochlorophyll c and chlorosomes. Cultures of thermophilic chlorobia grew only under anaerobic, phototrophic conditions, either photoautotrophically or photoheterotrophically. The optimum growth temperature for the strains of thermophilic green sulfur bacteria isolated was 47–48°C with generation times of about 2 h being observed. The upper temperature limit for growth was about 52°C. Thiosulfate was a major electron donor for photoautotrophic growth while sulfide alone was only poorly used. N_2 fixation was observed at 48°C and cell suspensions readily reduced acetylene to ethylene. The G+C content of DNA from strains of thermophilic chlorobia was 56.5–58.2 mol% and the organisms positioned phylogenetically within the green sulfur bacterial branch of the domain Bacteria. The new phototrophs are described as a new species of the genus Chlorobium, Chlorobium tepidum .
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Structures of Bacteriochlorophyll c’s in Chlorosomes from a New Thermophilic Bacterium Chlorobium tepidum
Chemistry Letters, 1991Co-Authors: Tsunenori Nozawa, Katsunori Ohtomo, Manabu Suzuki, Yumi Morishita, Michael T. MadiganAbstract:A new thermophilic bacterium Chlorobium tepidum contained two major bacteriochlorophyll c components whose periphery substituent at 4-position was either an ethyl or a propyl group. Both components possessed ethyl groups at 5-position and the ester alkyl groups at 7-position were farnesyl groups.
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Aggregation Structure of Bacteriochlorophyll c in Chlorosomes from Chlorobium tepidum.
Chemistry Letters, 1991Co-Authors: Tsunenori Nozawa, Katsunori Ohtomo, Manabu Suzuki, Yumi Morishita, Hideo Konami, Michael T. MadiganAbstract:High resolution solid state 13C NMR signals of bacteriochlorophyll (BChl) c were obtained for chlorosomes from Chlorobium tepidum. Observed BChl c signals which resembled those from oligomeric BChl c afforded ring current shift from which an aggregation structure was proposed.
Günter Hauska - One of the best experts on this subject based on the ideXlab platform.
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P840-reaction centers from Chlorobium tepidum-quinone analysis and functional reconstitution into lipid vesicles
Photochemistry and Photobiology, 1996Co-Authors: Nicole Frankenberg, Nathan Nelson, Christine Hager-braun, Ute Feiler, Markus Fuhrmann, Hans Rogl, Nikolaus Schneebauer, Günter HauskaAbstract:Membranes of Chlorobium tepidum contain about 35, 45 and2–10 molecules of menaquinone-7, Chlorobium quinone (1′-oxo-menaquinone-7) and of the polar menaquinone (probably 1′-OH-menaquinone-7) per reaction center, respectively. None of these quinones was retained during the isolation of P840-reaction centers beyond the detection limit of about 0.2 quinones per reaction center, neither in the core complex nor in functionally intact reaction center preparations. The latter is shown to catalyze the formation of an electrochemical proton gradient in the presence of ascorbate and phenazinium methosulfate, when it is incorporated into lipid vesicles.
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stable photobleaching of p840 in Chlorobium reaction center preparations presence of the 42 kda bacteriochlorophyll a protein and a 17 kda polypeptide
Biochemistry, 1995Co-Authors: Christine Hagerbraun, Günter Hauska, Dian-lin Xie, Michael Büttner, R. Deutzmann, U Jarosch, E Herold, R Zimmermann, Nathan NelsonAbstract:Simple procedures for the anaerobic preparation of photoactive and stable P840 reaction centers from Chlorobium tepidum and Chlorobium limicola in good yield are presented and quantitated. The subunit composition was tested by cosedimentation in sucrose density gradients. For C. limicola, it minimally comprises four subunits: the P840 reaction center protein PscA, the BChla antenna protein FMO, the FeS protein PscB with centers A and B, and a positively charged 17-kDa protein denoted PscD. The preparation from Chlorobium tepidum additionally contained PscC, a cytochrome c-551. The BChla absorption peak of the purified complexes was at 810 nm, with a shoulder at 835 nm. The ratio of the shoulder to the peak was 0.25, which corresponds to 1 reaction center per 70 BChla molecules if a uniform extinction coefficient of BChla is assumed. However, bleaching at 610 nm in continuous light corresponded up to 1 photoactive reaction center per 50 BChla molecules. Therefore, either the extinction coefficient of BChla in the reaction center is overestimated or the one for photobleaching is underestimated. In any case, the major portion of the reaction center was photoactive in the preparations. A P840 reaction center subcomplex, lacking PscD and deficient in FMO and PscB, but retaining the cytochrome c subunit, was obtained as a side product. It was photoinactive and had an absorption peak at 814 nm and a 835/814 absorbance ratio of 0.42. FMO and PscB show the tendency to form a complementary subcomplex. FMO and PscD are apparently required to stabilize the photoactive reaction center, while the cytochrome c subunit is not.
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A transcription unit for the Rieske FeS-protein and cytochrome b in Chlorobium limicola.
Photosynthesis research, 1994Co-Authors: Michael Schütz, Dian-lin Xie, Nathan Nelson, S. Zirngibl, J. Le Coutre, Michael Büttner, R. Deutzmann, Günter HauskaAbstract:A transcription unit petCB from Chlorobium limicola is described. The leading gene petC codes for a Rieske FeS-protein of 19.04 kDa with 181 amino acid residues. The following gene petB codes for a cytochrome b of 47.48 kDa with 428 amino acid residues. The transcription unit lacks a third gene pet-A for cytochrome c1 or-f, which is found in the fbc-operons of gram-negative bacteria. In the derived amino acid sequence for the Rieske FeS-protein the four cysteines and the 2 histidines are conserved in the peptides binding the 2Fe2S-cluster, although the redox potential of the cluster is about 150 mV more negative in Chlorobium. The gene for cytochrome b includes the coding region for an N-terminal, positively charged extension which is typical for Chlorobium. The gene is not split into two parts for cytochrome b6 and subunit IV. However, a fourteenth amino acid between the two histidines in the fourth, putative transmembrane helix, and the lack of an eighth transmembrane helix at the C-terminus, among other features, clearly resemble the cytochrome b6f-complexes. Therefore, the separation into b6f- and bc1-type complexes during evolution must have occurred before the split of the gene.
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The atp2 operon of the green bacterium Chlorobium limicola
Biochimica et biophysica acta, 1993Co-Authors: Dian-lin Xie, Günter Hauska, Holger Lill, Masatomo Maeda, Masamitsu Futai, Nathan NelsonAbstract:Abstract The operon (atp2) encoding the β and ϵ subunits of F-ATPase from Chlorobium limicola was cloned and sequenced. In contrast with purple bacteria these genes are arranged in a separate operon similar to the cyanobacteria. The operon terminates with a pronounced stem-loop structure. About 0.8 kb upstream of the β subunit a gene encoding the enzyme phospho enol pyruvate carboxykinase was identified. This gene is transcribed in the opposite direction of the atp2 operon and also ends with a stem-loop structure. These genes of green bacteria are among the first to be sequenced, and therefore the genetic distance between these genes and corresponding genes from other bacteria and eukaryotes was studied. Even though the operon structure resembles that of cyanobacteria, the evolutionary tree compiled from these data places the Chlorobium gene close to purple bacteria. Chlorobium limicola β and ϵ subunits complemented Escherichia coli mutants defective in the corresponding subunits, indicating that the hybrid enzyme formed from subunits of the two bacteria is active in ATP synthesis.
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Sulfide-quinone reductase (SQR) activity in Chlorobium.
FEBS letters, 1992Co-Authors: Yosepha Shahak, Boaz Arieli, Etana Padan, Günter HauskaAbstract:Membranes of the green sulfur bacterium, Chlorobium limicola f, thiosulfatophilum, catalyze the reduction of externally added isoprenoid quinones by sulfide. This activity is highly sensitive to stigmatellin and aurachins. It is also inhibited by 2-n-nonyl-4-hydroxyquinoline-N-oxide, antimycin, myxothiazol and cyanide. It is concluded that in sulfide oxidizing bacteria like Chlorobium, sulfide oxidation involves a sulfide-quinone reductase (SQR) similar to the one found in Oscilatoria limnetica [Arieli, B., Padan, E. and Shahak, Y. (1991) J. Biol. Chem. 266. 104–111].
Thomas E. Hanson - One of the best experts on this subject based on the ideXlab platform.
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a ribulose 1 5 bisphosphate carboxylase oxygenase rubisco like protein from Chlorobium tepidum that is involved with sulfur metabolism and the response to oxidative stress
Proceedings of the National Academy of Sciences of the United States of America, 2001Co-Authors: Thomas E. Hanson, F R TabitaAbstract:A gene encoding a product with substantial similarity to ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) was identified in the preliminary genome sequence of the green sulfur bacterium Chlorobium tepidum. A highly similar gene was subsequently isolated and sequenced from Chlorobium limicola f.sp. thiosulfatophilum strain Tassajara. Analysis of these amino acid sequences indicated that they lacked several conserved RubisCO active site residues. The Chlorobium RubisCO-like proteins are most closely related to deduced sequences in Bacillus subtilis and Archaeoglobus fulgidus, which also lack some typical RubisCO active site residues. When the C. tepidum gene encoding the RubisCO-like protein was disrupted, the resulting mutant strain displayed a pleiotropic phenotype with defects in photopigment content, photoautotrophic growth and carbon fixation rates, and sulfur metabolism. Most important, the mutant strain showed substantially enhanced accumulation of two oxidative stress proteins. These results indicated that the C. tepidum RubisCO-like protein might be involved in oxidative stress responses and/or sulfur metabolism. This protein might be an evolutional link to bona fide RubisCO and could serve as an important tool to analyze how the RubisCO active site developed.
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A ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO)-like protein from Chlorobium tepidum that is involved with sulfur metabolism and the response to oxidative stress
Proceedings of the National Academy of Sciences of the United States of America, 2001Co-Authors: Thomas E. HansonAbstract:A gene encoding a product with substantial similarity to ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) was identified in the preliminary genome sequence of the green sulfur bacterium Chlorobium tepidum. A highly similar gene was subsequently isolated and sequenced from Chlorobium limicola f.sp. thiosulfatophilum strain Tassajara. Analysis of these amino acid sequences indicated that they lacked several conserved RubisCO active site residues. The Chlorobium RubisCO-like proteins are most closely related to deduced sequences in Bacillus subtilis and Archaeoglobus fulgidus, which also lack some typical RubisCO active site residues. When the C. tepidum gene encoding the RubisCO-like protein was disrupted, the resulting mutant strain displayed a pleiotropic phenotype with defects in photopigment content, photoautotrophic growth and carbon fixation rates, and sulfur metabolism. Most important, the mutant strain showed substantially enhanced accumulation of two oxidative stress proteins. These results indicated that the C. tepidum RubisCO-like protein might be involved in oxidative stress responses and/or sulfur metabolism. This protein might be an evolutional link to bona fide RubisCO and could serve as an important tool to analyze how the RubisCO active site developed.
Donald A. Bryant - One of the best experts on this subject based on the ideXlab platform.
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The bchU gene of Chlorobium tepidum encodes the c-20 methyltransferase in bacteriochlorophyll c biosynthesis.
Journal of bacteriology, 2004Co-Authors: Julia A. Maresca, John G. Ormerod, Aline Gomez Maqueo Chew, Marta Ros Ponsatí, Niels-ulrik Frigaard, Donald A. BryantAbstract:Bacteriochlorophylls (BChls) c and d, two of the major light-harvesting pigments in photosynthetic green sulfur bacteria, differ only by the presence of a methyl group at the C-20 methine bridge position in BChl c. A gene potentially encoding the C-20 methyltransferase, bchU, was identified by comparative analysis of the Chlorobium tepidum and Chloroflexus aurantiacus genome sequences. Homologs of this gene were amplified and sequenced from Chlorobium phaeobacteroides strain 1549, Chlorobium vibrioforme strain 8327d, and C. vibrioforme strain 8327c, which produce BChls e, d, and c, respectively. A single nucleotide insertion in the bchU gene of C. vibrioforme strain 8327d was found to cause a premature, in-frame stop codon and thus the formation of a truncated, nonfunctional gene product. The spontaneous mutant of this strain that produces BChl c (strain 8327c) has a second frameshift mutation that restores the correct reading frame in bchU. The bchU gene was inactivated in C. tepidum, a BChl c-producing species, and the resulting mutant produced only BChl d. Growth rate measurements showed that BChl c- and d-producing strains of the same organism (C. tepidum or C. vibrioforme) have similar growth rates at high and intermediate light intensities but that strains producing BChl c grow faster than those with BChl d at low light intensities. Thus, the bchU gene encodes the C-20 methyltransferase for BChl c biosynthesis in Chlorobium species, and methylation at the C-20 position to produce BChl c rather than BChl d confers a significant competitive advantage to green sulfur bacteria living at limiting red and near-infrared light intensities.
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Insertional inactivation studies of the csmA and csmC genes of the green sulfur bacterium Chlorobium vibrioforme 8327: the chlorosome protein CsmA is required for viability but CsmC is dispensable
FEMS microbiology letters, 1998Co-Authors: Soohee Chung, John G. Ormerod, Gaozhong Shen, Donald A. BryantAbstract:Targeted mutagenesis was used to investigate the roles of the CsmA and CsmC proteins of the chlorosomes of the green bacteria Chlorobium tepidum and Chlorobium vibrioforme 8327. Under the photoautotrophic growth conditions employed, CsmA is required for the viability of the cells but CsmC is dispensable. The absence of CsmC caused a small red shift in the near-infrared absorption maximum of bacteriochlorophyll d in whole cells and chlorosomes, but chlorosomes were assembled in and could be isolated from the csmC mutant. The doubling time of the csmC mutant was approximately twice that of the wild-type strain. Fluorescence emission measurements suggested that energy transfer from the bulk bacteriochlorophyll d to another pigment, perhaps bacteriochlorophyll a, emitting at 800–804 nm, was less efficient in the csmC mutant cells than in wild-type cells. These studies establish that transformation and homologous recombination can be employed in targeted mutagenesis of Chlorobium sp. and further demonstrate that chlorosome proteins play important roles in the structure and function of these light-harvesting organelles.
Michael A. Cusanovich - One of the best experts on this subject based on the ideXlab platform.
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Identification of a thiosulfate utilization gene cluster from the green phototrophic bacterium Chlorobium limicola.
Biochemistry, 2002Co-Authors: Fabienne Verte, Terrance E. Meyer, Michael A. Cusanovich, Vesna Kostanjevecki, L. De Smet, J. Van BeeumenAbstract:Chlorobium is an autotrophic, green phototrophic bacterium which uses reduced sulfur compounds to fix carbon dioxide in the light. The pathways for the oxidation of sulfide, sulfur, and thiosulfate have not been characterized with certainty for any species of bacteria. However, soluble cytochrome c-551 and flavocytochrome c (FCSD) have previously been implicated in the oxidation of thiosulfate and sulfide on the basis of enzyme assays in Chlorobium. We have now made a number of observations relating to the oxidation of reduced sulfur compounds. (1) Western analysis shows that soluble cytochrome c-551 in Chlorobium limicola is regulated by thiosulfate, consistent with a role in the utilization of thiosulfate. (2) A membrane-bound flavocytochrome c-sulfide dehydrogenase (which is normally a soluble protein in other species) is constitutive and not regulated by sulfide as expected for an obligately autotrophic species dependent upon sulfide. (3) We have cloned the cytochrome c-551 gene from C. limicola and have found seven other genes, which are also presumably involved in sulfur metabolism and located near that for cytochrome c-551 (SoxA). These include genes for a flavocytochrome c flavoprotein homologue (SoxF2), a nucleotidase homologue (SoxB), four small proteins (including SoxX, SoxY, and SoxZ), and a thiol-disulfide interchange protein homologue (SoxW). (4) We have established that the constitutively expressed FCSD genes (soxEF1) are located elsewhere in the genome. (5) Through a database search, we have found that the eight thiosulfate utilization genes are clustered in the same order in the Chlorobium tepidum genome (www.tigr.org). Similar thiosulfate utilization gene clusters occur in at least six other bacterial species but may additionally include genes for rhodanese and sulfite dehydrogenase.
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Redox potentials of flavocytochromes c from the phototrophic bacteria, Chromatium vinosum and Chlorobium thiosulfatophilum
Archives of biochemistry and biophysics, 1991Co-Authors: Terrance E. Meyer, R.g. Bartsch, Michael Caffrey, Michael A. CusanovichAbstract:Abstract The redox potentials of flavocytochromes c (FC) from Chromatium vinosum and Chlorobium thiosulfatophilum have been studied as a function of pH. Chlorobium FC has a single heme which has a redox potential of +98 mV at pH 7 (N = 1) that is independent of pH between 6 and 8. The average two-electron redox potential of the flavin extrapolated to pH 7 is +28 mV and decreases 35 mV/ pH between pH 6 and 7. The anionic form of the flavin semiquinone is stabilized above pH 6. The redox potential of Chromatium FC is markedly lower than for Chlorobium. The two hemes in Chromatium FC appear to have a redox potential of 15 mV at pH 7 (N = 1), although they reside in very different structural environments. The hemes of Chromatium FC have a pH-dependent redox potential, which can be fit in the simplest case by a single ionization with pK = 7.05. The flavin in Chromatium FC has an average two-electron redox potential of −26 mV at pH 7 and decreases 30 mV/pH between pH 6 and 8. As with Chlorobium, the anionic form of the flavin semiquinone of Chromatium FC is stabilized above pH 6. The unusually high redox potential of the flavin, a stabilized anion radical, and sulfite binding to the flavin in both Chlorobium and Chromatium FCs are characteristics shared by the flavoprotein oxidases. By analogy with glycolate oxidase and lactate dehydrogenase for which there are three-dimensional structures, the properties of the FCs are likely to be due to a positively charged amino acid side chain in the vicinity of the N1 nitrogen of the flavin.