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Aharon Oren - One of the best experts on this subject based on the ideXlab platform.
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Fate of compatible solutes during dilution stress in Ectothiorhodospira marismortui
FEMS Microbiology Letters, 1993Co-Authors: Uri Fischel, Aharon OrenAbstract:Ectothiorhodospira marismortui, a halophlic purple sulfur bacterium isolated from a sulfur spring on the shore of the Dead Sea, accumulates three organic solutes to achieve osmotic balance with the medium: glycine betaine, Nα-carbamoyl-l-glutamine 1-amide (CGA), and a minor amount of sucrose. When cells were subjected to dilution stress, part of the glycine betaine was excreted into the medium during the first 5–10 min, to be taken up again at a later stage. Intracellular concentrations of both CGA and sucrose decreased within 1–2 h to a new level corresponding with the lowered salinity. Neither CGA, nor sucrose appeared in the medium, showing that these compounds are metabolized intracellularly. When the decrease in intracellular CGA concentration was followed by assays for amide groups and for carbamoyl groups, it appeared that the decrease in carbamoyl groups containing material was much more rapid than the decrease in amide groups, suggesting l-glutamine 1-amide as a possible intermediate of CGA degradation.
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Isolation and structure determination of a novel compatible solute from the moderately halophilic purple sulfur bacterium Ectothiorhodospira marismortui
European journal of biochemistry, 1991Co-Authors: Erwin A. Galinski, Aharon OrenAbstract:The halophilic phototrophic bacterium Ectothiorhodospira marismortui produces three organic osmolytes to counterbalance the osmotic pressure of the surrounding medium: glycine betaine, sucrose, and a novel compound. This new compound, which accounts for approximately 30% of the cells' compatible solutes, was isolated and identified by mass spectrometry and nuclear magnetic resonance. It was characterized as N alpha-carbamoyl-L-glutamine 1-amide, an unusual amino acid derivative with no previous reference in the chemical literature. The relatively high cytoplasmic concentration of this compound (approximately 0.5 M) observed at all growth conditions suggests that it may serve a vital function as an osmoticum and/or protectant for Ectothiorhodospira marismortui in a saline environment.
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isolation and structure determination of a novel compatible solute from the moderately halophilic purple sulfur bacterium Ectothiorhodospira marismortui
FEBS Journal, 1991Co-Authors: Erwin A. Galinski, Aharon OrenAbstract:The halophilic phototrophic bacterium Ectothiorhodospira marismortui produces three organic osmolytes to counterbalance the osmotic pressure of the surrounding medium: glycine betaine, sucrose, and a novel compound. This new compound, which accounts for approximately 30% of the cells' compatible solutes, was isolated and identified by mass spectrometry and nuclear magnetic resonance. It was characterized as Nα-carbamoyl-l-glutamine 1-amide, an unusual amino acid derivative with no previous reference in the chemical literature. The relatively high cytoplasmic concentration of this compound (∼ 0.5 M) observed at all growth conditions suggests that it may serve a vital function as an osmoticum and/or protectant for Ectothiorhodospira marismortui in a saline environment.
Lucia Banci - One of the best experts on this subject based on the ideXlab platform.
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identification of slow motions in the reduced recombinant high potential iron sulfur protein i hipip i from Ectothiorhodospira halophila via 15n rotating frame nmr relaxation measurements
Journal of Biomolecular NMR, 1998Co-Authors: Lucia Banci, Isabella C. Felli, Dionysios KoulougliotisAbstract:Rotating-frame 15N relaxation rate (R1ρ) NMR experiments have been performed in order to study the dynamic behavior of the reduced recombinant high-potential iron-sulfur protein iso I (HiPIP I) from Ectothiorhodospira halophila, in the μs to ms time range. Measurements of R1ρ were performed as a function of the effective spin-lock magnetic field amplitude by using both on and off-resonance radio frequency irradiation. The two data sets provided consistent results and were fit globally in order to identify possible exchange processes in an external loop of the reduced HiPIP I. The loop consists of residues 43-45 and the correlation time of the exchange process was determined to be 50 ± 8 μs for the backbone nitrogen of Gln 44.
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Identification of Slow Motions in the Reduced Recombinant High-potential Iron Sulfur Protein I (HiPIP I) from Ectothiorhodospira Halophila via 15N Rotating-frame NMR Relaxation Measurements
Journal of biomolecular NMR, 1998Co-Authors: Lucia Banci, Isabella C. Felli, Dionysios KoulougliotisAbstract:Rotating-frame 15N relaxation rate (R1 rho) NMR experiments have been performed in order to study the dynamic behavior of the reduced recombinant high-potential iron-sulfur protein iso I (HiPIP I) from Ectothiorhodospira halophila, in the microsecond to ms time range. Measurements of R1 rho were performed as a function of the effective spinlock magnetic field amplitude by using both on and off-resonance radio frequency irradiation. The two data sets provided consistent results and were fit globally in order to identify possible exchange processes in an external loop of the reduced HiPIP I. The loop consists of residues 43-45 and the correlation time of the exchange process was determined to be 50 +/- 8 microseconds for the backbone nitrogen of Gln 44.
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The electronic structure of iron-sulfur [Fe4S4]3+ clusters in proteins. An investigation of the oxidized high-potential iron-sulfur protein II from Ectothiorhodospira vacuolata
Biochemistry, 1993Co-Authors: Lucia Banci, Ivano Bertini, Claudio Luchinat, Stefano Ciurli, Silvia Ferretti, Mario PiccioliAbstract:Within the framework of an investigation of the electronic structure of oxidized high-potential iron-sulfur proteins (HiPIP), we have studied the HiPIP II from Ectothiorhodospira vacuolata, which was known to have a peculiar temperature dependence of the 1H NMR isotropic hyperfine shifts. The signals of the cysteine ligand protons have been sequence specifically assigned through NOE, NOESY, and TOCSY experiments. Nine hyperfine-shifted signals are observed: seven in the downfield and two in the upfield region. They have been assigned to the eight beta-CH2 protons of the four coordinated cysteines and to one alpha-CH cysteine proton. The two most downfield-shifted signals belong to the beta-CH2 protons of Cys 63 (Chromatium vinosum numbering) and the two upfield protons to those of Cys 43. These two pairs of protons show a Curie-type temperature dependence of the hyperfine shifts. Among the remaining five downfield-shifted signals, three show a Curie-type temperature dependence and two have an anti-Curie temperature dependence. The former are assigned to the beta-CH2 and alpha-CH protons of Cys 77 and the latter to the beta-CH2 protons of Cys 46. The shift patterns are thus similar, in a sequence-specific sense, to those of the analogous proteins from C. vinosum and Rhodocyclus gelatinosus, whereas they differ from those of Rhodocyclus globiformis HiPIP and even more from those of Ectothiorhodospira halophila HiPIP II. Oxidized HiPIPs can be formally viewed as containing a cluster of four ferric ions plus one extra electron. We present here a model based on a chemical equilibrium, fast on the NMR time scale, between two species, both of which contain a pair of iron(III) ions and a mixed-valence pair but are differently oriented within the protein frame. The EPR data are also discussed in the light of the debate on the nature of the different species detected at low temperature. The interpretation of the whole set of data on HiPIPs in the light of the present model is compared with that based on previous models.
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the iron sulfur cluster in the oxidized high potential iron protein from Ectothiorhodospira halophila
Journal of the American Chemical Society, 1993Co-Authors: Lucia Banci, Ivano Bertini, Claudio Luchinat, Francesco Capozzi, Paolo Carloni, Stefano Ciurli, Mario PiccioliAbstract:In our efforts to characterize oxidized high-potential iron-sulfur proteins (HiPIP), we have investigated the oxidized HiPIP II from Ectothiorhodospira halophila through 1 H NMR and molecular dynamics (MD) calculations. This protein has the most symmetric isotropic shift pattern of the β-CH 2 protons of the liganded cysteines, four signals being upfield and four downfield. 1 H NOE, NOESY, and TOCSY results have provided the necessary key connectivities to perform the assignment of the liganded cysteines, taking advantage of the structure of the HiPIP I isoprotein. It is found that the electronic distribution within the cluster is different with respect to the Chromatium vinosum and Rhodocyclus gelatinosus systems
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1h noe studies of oxidized high potential iron sulfur protein ii from Ectothiorhodospira halophila
Inorganica Chimica Acta, 1991Co-Authors: Lucia Banci, Ivano Bertini, Fabrizio Briganti, Andrea Scozzafava, Margarita Vicens Oliver, Claudio LuchinatAbstract:Abstract The 1 H NMR spectra of oxidized HiPIP II from Ectothiorhodospira halophila have been recorded at 600 MHz. Nuclear Overhauser effect measurements have allowed the assignment of the cysteine β-CH 2 resonances. Four β-CH 2 signals are downfield shifted and four upfield shifted. Through a theoretical model and on the ground of Mossbauer data on analogous systems we propose that the upfield signals are those of the cysteines bound to the iron(III) ions and those downfield of the cysteines bound to the mixed valence pair Fe(III)-Fe(II).
Johannes F. Imhoff - One of the best experts on this subject based on the ideXlab platform.
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Ectothiorhodospira variabilis sp. nov., an alkaliphilic and halophilic purple sulfur bacterium from soda lakes.
International journal of systematic and evolutionary microbiology, 2009Co-Authors: V. M. Gorlenko, I. A. Bryantseva, T. P. Tourova, Sandra Rabold, Dariya Rubtsova, Ekaterina Smirnova, Vera Thiel, Johannes F. ImhoffAbstract:During studies of moderately halophilic strains of Ectothiorhodospira from steppe soda lakes, we found a novel group of bacteria related to Ectothiorhodospira haloalkaliphila with salt optima at 50-80 g NaCl l(-1). Phylogenetic analysis using 16S rRNA gene sequences of strains from soda lakes in Mongolia, Egypt and Siberia revealed separation of the group of new isolates from other Ectothiorhodospira species, including the closely related Ect. haloalkaliphila. DNA-DNA hybridization studies demonstrated that the new isolates form a homogeneous group at the species level, but at the same time are distinct from related species such as Ect. haloalkaliphila, Ect. vacuolata, Ect. shaposhnikovii and Ect. marina. The new isolates are considered to be strains of a novel species, for which the name Ectothiorhodospira variabilis sp. nov. is proposed, with the type strain WN22(T) (=VKM B-2479(T) =DSM 21381(T)). Photosynthetic pigments of the novel species are bacteriochlorophyll a and carotenoids of the spirilloxanthin series with spirilloxanthin and derivatives thereof, together with small amounts of lycopene and rhodopin. Gas vesicles are formed by most of the strains, particularly in media containing yeast extract (0.5 g l(-1)) and acetate (0.5-2.0 g l(-1)). Sequence analysis of nifH (nitrogenase) and cbbL (RuBisCO) confirmed the assignment of the strains to the genus Ectothiorhodospira and in particular the close relationship to Ect. haloalkaliphila. The novel species Ect. variabilis is found in soda lakes separated by great geographical distances and is an alkaliphilic and halophilic bacterium that tolerates salt concentrations up to 150-200 g NaCl l(-1).
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The porins from the halophilic species Ectothiorhodospira shaposhnikovii and Ectothiorhodospira vacuolata
Archives of microbiology, 1996Co-Authors: E. Wolf, Johannes F. Imhoff, M. Zahr, Roland Benz, A. Lustig, Emile Schiltz, J. Stahl-zeng, J. WeckesserAbstract:Major outer membrane proteins with porin activity were isolated from cell envelopes of the halophilic strains Ectothiorhodospira shaposhnikovii N1 and Ectothiorhodospira vacuolata beta1. The porins were obtained as oligomers. They dissociated into monomers by heat or EDTA treatment. The molecular masses of the monomers were determined by mass spectrometry to be 39,285 and 37,160 Da for E. shaposhnikovii N1 and E. vacuolata beta1, respectively. Both were shown by analytical ultracentrifugation to be trimers of about 112, 000 Da. Circular dichroism spectra indicated predominantly beta-sheet structure. The 18 N-terminal amino acid sequences of the two porins were identical except for the amino acids in positions 12 and 14. No sequence similarity with the primary structure of known porins was found. In reconstitution experiments with lipid bilayers, the porins of E. shaposhnikovii N1 and E. vacuolata beta1 formed channels with a single-channel conductance of 1.5 and 0.7 nS, respectively, in 1 M KCl. The single-channel conductance saturated with increasing salt concentration, indicating a putative binding-site for anions in the channel since both porins exhibited anion-selectivity. For the porin of E. vacuolata beta1, but not for that of E. shaposhnikovii N1, an influence of detergent concentration on the single-channel conductance was observed.
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the porins from the halophilic species Ectothiorhodospira shaposhnikovii and Ectothiorhodospira vacuolata
Archives of Microbiology, 1996Co-Authors: E. Wolf, Johannes F. Imhoff, M. Zahr, Roland Benz, A. Lustig, Emile Schiltz, J Stahlzeng, J. WeckesserAbstract:Major outer membrane proteins with porin activity were isolated from cell envelopes of the halophilic strains Ectothiorhodospira shaposhnikovii N1 and Ectothiorhodospira vacuolataβ1. The porins were obtained as oligomers. They dissociated into monomers by heat or EDTA treatment. The molecular masses of the monomers were determined by mass spectrometry to be 39,285 and 37,160 Da for E. shaposhnikovii N1 and E. vacuolataβ1, respectively. Both were shown by analytical ultracentrifugation to be trimers of about 112,000 Da. Circular dichroism spectra indicated predominantly β-sheet structure. The 18 N-terminal amino acid sequences of the two porins were identical except for the amino acids in positions 12 and 14. No sequence similarity with the primary structure of known porins was found. In reconstitution experiments with lipid bilayers, the porins of E. shaposhnikovii N1 and E. vacuolataβ1 formed channels with a single-channel conductance of 1.5 and 0.7 nS, respectively, in 1 M KCl. The single-channel conductance saturated with increasing salt concentration, indicating a putative binding-site for anions in the channel since both porins exhibited anion-selectivity. For the porin of E. vacuolataβ1, but not for that of E. shaposhnikovii N1, an influence of detergent concentration on the single-channel conductance was observed.
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The phylogenetic relationship among Ectothiorhodospiraceae: a reevaluation of their taxonomy on the basis of 16S rDNA analyses
Archives of Microbiology, 1996Co-Authors: Johannes F. Imhoff, Jörg SülingAbstract:Sequences of the 16S rRNA gene were determined from all type strains of the recognized Ectothiorhodospira species and from a number of additional strains. For the first time, these data resolve the phylogenetic relationships of the Ectothiorhodospiraceae in detail, confirm the established species, and improve the classification of strains of uncertain affiliation. Two major groups that are recognized as separate genera were clearly established. The extremely halophilic species were removed from the genus Ectothiorhodospira and reassigned to the new genus Halorhodospira gen. nov., to recognize that the most halophilic eubacteria are species of this genus. These species are Halorhodospira halophila comb. nov., Halorhodospira halochloris comb. nov., and Halorhodospira abdelmalekii comb. nov. Among the slightly halophilic Ectothiorhodospira species, the classification of strains belonging to Ectothiorhodospira mobilis and Ectothiorhodospira shaposhnikovii was improved. Several strains that were tentatively identified as Ectothiorhodospira mobilis form a separate cluster on the basis of their 16S rDNA sequences and are recognized as two new species: Ectothiorhodospira haloalkaliphila sp. nov., which includes the most alkaliphilic strains originating from strongly alkaline soda lakes, and Ectothiorhodospira marina, describing isolates from the marine environment.
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Differentiation of Ectothiorhodospiraceae based on their fatty acid composition
Systematic and Applied Microbiology, 1996Co-Authors: Bernhard Thiemann, Johannes F. ImhoffAbstract:The fatty acid composition of 27 strains from 7 described Ectothiorhodospira species, including all type strains, were analyzed and compared using the “Microbial Identification System”. According to their ability to grow in media with 15% total salts and more or to require much lower salt concentrations the comparison of the strains was made in two different groups. The strains grown in the established standard medium for Ectothiorhodospira species at 15% and 25% (w/v) salinity formed four major clusters. Two of these enclosed strains of E. halophila, the others E. abdelmalekii (one strain) and E. halochloris (3 strains), respectively. Those strains with salt optima significantly below 10% (w/v) salinity formed three major clusters. The first included strains of E. mobilis and E. marismortui. The second cluster contained strains of E. shaposhnikovii, E. vacuolata and one strain that had been tentatively identified as E. mobilis but should be considered as a strain of E. shaposhnikovii. The third group contained strains that were assigned to E. mobilis but should be regarded as a separate and new species. The observed similarities support and extend patterns of relationships obtained by other taxonomic investigations on the basis of a smaller number of strains.
Herbert Zuber - One of the best experts on this subject based on the ideXlab platform.
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The primary structure of the antenna polypeptides of Ectothiorhodospira halochloris and Ectothiorhodospira halophila. Four core-type antenna polypeptides in E. halochloris and E. halophila.
European journal of biochemistry, 1992Co-Authors: Regula Wagner-huber, René A. Brunisholz, Iwan Bissig, Gerhard Frank, Franz Suter, Herbert ZuberAbstract:Antenna polypeptides from two species of the family Ectothiorhodospiraceae have been investigated. By means of gel filtration and subsequent high-performance liquid chromatography, at least five polypeptides were isolated from each of Ectothiorhodospira halochloris and Ectothiorhodospira halophila. The majority of their primary structures was identified by Edman degradation. Comparison of these polypeptide sequences with the known primary structures of antenna polypeptides from various purple non-sulfur bacteria revealed interesting new aspects with regard to the structure of the core-peripheral antenna system. E. halochloris and E. halophila contain two pairs of alpha- and beta-polypeptides each with typical primary structure elements of core complexes, indicating a modified antenna complex organization.
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The primary structure of the antenna polypeptides of Ectothiorhodospira halochloris and Ectothiorhodospira halophila. Four core-type antenna polypeptides in E. halochloris and E. halophila.
European Journal of Biochemistry, 1992Co-Authors: Regula Wagner-huber, René A. Brunisholz, Iwan Bissig, Gerhard Frank, Franz Suter, Herbert ZuberAbstract:Antenna polypeptides from two species of the family Ectothiorhodospiraceae have been investigated. By means of gel filtration and subsequent high-performance liquid chromatography, at least five polypeptides were isolated from each of Ectothiorhodospira halochloris and Ectothiorhodospira halophila. The majority of their primary structures was identified by Edman degradation. Comparison of these polypeptide sequences with the known primary structures of antenna polypeptides from various purple non-sulfur bacteria revealed interesting new aspects with regard to the structure of the core-peripheral antenna system. E. halochloris and E. halophila contain two pairs of α- and β-polypeptides each with typical primary structure elements of core complexes, indicating a modified antenna complex organization.
Mario Piccioli - One of the best experts on this subject based on the ideXlab platform.
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Electron self-exchange in high-potential iron-sulfur proteins. Characterization of protein I from Ectothiorhodospira vacuolata.
Biochemistry, 1993Co-Authors: Ivano Bertini, Claudio Luchinat, Alain Gaudemer, Mario PiccioliAbstract:During previous research on oxidized and reduced high-potential iron-sulfur proteins (HiPIP hereafter), qualitative different electron self-exchange rates were noticed. We have now investigated this phenomenon in detail for HiPIP I and II from Ectothiorhodospira vacuolata, which differ significantly in total charge and in which the sequence homology is the largest among all known HiPIPs. We have also characterized the electronic structure of HiPIP I through 1H NMR and EPR spectroscopies to parallel the existing characterization of HiPIP II and other HiPIPs. This investigation has allowed us to propose a model, according to which the productive collisions for electron transfer occur through a hydrophobic patch near the cluster. The effects of total charge and redox potential are considered. The possible formation of dimers through the hydrophobic patch at liquid helium temperature is discussed in light of the EPR spectra.
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The electronic structure of iron-sulfur [Fe4S4]3+ clusters in proteins. An investigation of the oxidized high-potential iron-sulfur protein II from Ectothiorhodospira vacuolata
Biochemistry, 1993Co-Authors: Lucia Banci, Ivano Bertini, Claudio Luchinat, Stefano Ciurli, Silvia Ferretti, Mario PiccioliAbstract:Within the framework of an investigation of the electronic structure of oxidized high-potential iron-sulfur proteins (HiPIP), we have studied the HiPIP II from Ectothiorhodospira vacuolata, which was known to have a peculiar temperature dependence of the 1H NMR isotropic hyperfine shifts. The signals of the cysteine ligand protons have been sequence specifically assigned through NOE, NOESY, and TOCSY experiments. Nine hyperfine-shifted signals are observed: seven in the downfield and two in the upfield region. They have been assigned to the eight beta-CH2 protons of the four coordinated cysteines and to one alpha-CH cysteine proton. The two most downfield-shifted signals belong to the beta-CH2 protons of Cys 63 (Chromatium vinosum numbering) and the two upfield protons to those of Cys 43. These two pairs of protons show a Curie-type temperature dependence of the hyperfine shifts. Among the remaining five downfield-shifted signals, three show a Curie-type temperature dependence and two have an anti-Curie temperature dependence. The former are assigned to the beta-CH2 and alpha-CH protons of Cys 77 and the latter to the beta-CH2 protons of Cys 46. The shift patterns are thus similar, in a sequence-specific sense, to those of the analogous proteins from C. vinosum and Rhodocyclus gelatinosus, whereas they differ from those of Rhodocyclus globiformis HiPIP and even more from those of Ectothiorhodospira halophila HiPIP II. Oxidized HiPIPs can be formally viewed as containing a cluster of four ferric ions plus one extra electron. We present here a model based on a chemical equilibrium, fast on the NMR time scale, between two species, both of which contain a pair of iron(III) ions and a mixed-valence pair but are differently oriented within the protein frame. The EPR data are also discussed in the light of the debate on the nature of the different species detected at low temperature. The interpretation of the whole set of data on HiPIPs in the light of the present model is compared with that based on previous models.
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the iron sulfur cluster in the oxidized high potential iron protein from Ectothiorhodospira halophila
Journal of the American Chemical Society, 1993Co-Authors: Lucia Banci, Ivano Bertini, Claudio Luchinat, Francesco Capozzi, Paolo Carloni, Stefano Ciurli, Mario PiccioliAbstract:In our efforts to characterize oxidized high-potential iron-sulfur proteins (HiPIP), we have investigated the oxidized HiPIP II from Ectothiorhodospira halophila through 1 H NMR and molecular dynamics (MD) calculations. This protein has the most symmetric isotropic shift pattern of the β-CH 2 protons of the liganded cysteines, four signals being upfield and four downfield. 1 H NOE, NOESY, and TOCSY results have provided the necessary key connectivities to perform the assignment of the liganded cysteines, taking advantage of the structure of the HiPIP I isoprotein. It is found that the electronic distribution within the cluster is different with respect to the Chromatium vinosum and Rhodocyclus gelatinosus systems
