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PubMed2000

Model of detergent-induced spectral changes of the B800-850 complex from Chromatium minutissimum.

The absorption and circular dichroism spectra of the B800-850 complex from Chromatium minutissimum before and after the Triton X-100 treatment were simulated by means of standard exciton theory, taking into account inhomogeneous broadening. To explain the spectral changes of the B800-850 complex treated with Triton X-100, we have assumed that all bacteriochlorophyll pigments absorbing at 850 nm exhibit the same additional rotation of approximately 20 degrees around the axis perpendicular to the membrane plane. This has been sufficient to fit the transformation in absorption and circular dichroism spectra induced by detergent treatment of the B800-850 complex.

Absorption↗
PubMed1991

Temperature and solvent effects on reaction centers from Chloroflexus aurantiacus and Chromatium tepidum.

Temperature and solvent effects on reaction center structures were examined in two thermophilic photosynthetic bacteria, Chloroflexus aurantiacus and Chromatium tepidum, in order to gain insight into the interactions among the reaction center proteins and pigment systems. Thermal stability of the reaction centers was found to be proportional to the optimum growth temperature. Circular dichroism (CD) spectra in the 250-300 nm region indicated that thermal denaturation destroyed tertiary structures (helix-to-helix interactions or amino acid residue conformation) in the native reaction center, keeping helical structures intact. Absorption and circular dichroism spectral changes showed that alcohol denatured the so-called special pair and the accessory BChl a independently. The alcohol denaturation further indicates that the coordination between BChl a and amino acid residue in the protein is one of the important interactions maintaining the pigment organization of the reaction centers.

Alcohols↗
PubMed1977

Delayed fluorescence from bacteriochlorophyll in Chromatium vinosum chromatophores: characteristics in the presence of o-phenanthroline.

Delayed fluorescence from bacteriochlorophyll in the chromatophores of Chromatium vinosum, a photosynthetic purple sulfur bacterium, was studied in the presence of o-phenanthroline (o-phen) under intermittent illumination. Re-reduction of the photooxidized reaction center bacteriochlorophyll (P+) in the dark interval was accelerated by o-phen. This effect was attributed to the return of electrons trapped in the primary electron acceptor (A) to P+. In the presence of o-phen, the time course of the decay of delayed fluorescence was not coincident with that of the re-reduction of P+. The delayed fluorescence was somewhat intensified at the early stage (within 30 ms) of relaxation in the dark period. Prolonged illumination (longer than 20 ms) or uncouplers such as carbonylcyanide m-chlorophenylhydrazone (CCCP) or valinomycin plus nigericin decreased the intensity of delayed fluorescence and suppressed the stimulation of delayed fluorescence at the early stage. Delayed fluorescence from reaction center-rich subchromatophore particles decayed with a time course identical to that of the reduction of P+ and was not affected by CCCP, in the presence of o-phen. The intensification at the early stage in the chromatophores can be interpreted in terms of charge separation between pairs of P and A, primary electron donor and acceptor molecules, oriented perpendicular to the intact chromatophore membrane, the effect decreasing in parallel with the recombination of P+ and A-.

Bacterial Chromatophores↗
PubMed1977

Amino acid sequence of chromatium vinosum ferredoxin: revisions.

Reexamination of the amino acid sequence of chromatium vinosum ferredoxin revealed that the original sequence proposed in 1970 (I) should be revised. Two segments in the sequence, residues 50-52 and residues 53-57, should be mutually displaced and therefore, the correct sequence in this region is concluded to be -Val-Glu-Val-Cys-Pro-Val-Asp-Cys-(residues 50-57). Another correction was the addition of one isoleucine residue between residues 57 and 58 and therefore, the total number of residues should be 82 instead of 81 originally counted. Sequence studies of other portions confirmed the previous results.

Amino Acid Sequence↗
PubMed1977

Studies on the surface structure of the intracytoplasmic membrane in the photosynthetic purple bacterium Chromatium vinosum by means of chemical modification.

By means of a chemical modification technique, the surface structure of the intracytoplasmic membrane (chromatophores) of the photosynthetic bacterium Chromatium vinosum was investigated. Trinitrobenzenesulfonate was employed to modify the primary amino groups of phosphatidylethanolamine and proteins. The experimental results indicate that upon the chemical modification of intact cells, the amino groups on the inner surface of the chromatophores are trinitrophenylated, while upon the modification of isolated chromatophores, the amino groups of the outer surface are trinitrophenylated. Phosphatidylethanolamine is essentially equally distributed on the inner and outer surfaces of the chromatophores, while most proteins exist at the outer surface. In particular, a protein fraction, which is soluble in a mixture of chloroform/methanol, is located at the outer surface exposing a part of the amino groups in the aqueous phase.

Bacterial Chromatophores↗
PubMed1978

Chromatium sulfite reductase. I. Characterization of thiosulfate-forming activity at the cell extract level.

Thiosulfate and sulfide were detected in the sulfite reductase reaction catalyzed by a cell-free extract of photoautotrophically grown Chromatium vinosum. Hydrogen was consumed upon addition of sulfite to the extract in the presence of hydrogenase and methylviologen. Hydrogen uptake proceeded biphasically. During the first phase, thiosulfate and sulfide were formed concomitant with the decrease in sulfite. After the disappearance of sulfite, hydrogen was consumed with reduced velocity and sulfide accumulated as the final product with the total consumption of three mol of hydrogen per mol of sulfite. The molecular weight of a major sulfite reductase was estimated to be about 180,000 by the polyacrylamide disc electrophoresis method using enzyme staining. Arsenite. EDTA, alpha,alpha'-dipyridyl, cyanide, or azide did not inhibit the activity at the concentration of 1 mM. The activity was present in the soluble fraction and was stable at --20 degrees C.

2,2'-Dipyridyl↗
PubMed1979

Energetic coupling in the primary processes of photosynthesis in Chromatium. pH dependence of delayed fluorescence, electron transfer and degree of coupling.

The effects of pH on the thermodynamic properties of the proton-translocating cyclic electron transfer system in a purple photosynthetic bacterium Chromatium vinosum were studied. Two thermodynamic parameters, the flux (Je) and force (deltamue) of the electron transfer process, were analyzed. The rate of electron transfer in the re-reduction of photooxidized reaction-center bacteriochlorophyll was used as Je. deltamue was determined from the intensity of the delayed fluorescence from bacteriochlorophyll. deltamue is composed of the redox potential difference and the electrical potential difference between two electron transfer components. In the steady state under illumination, the flux-to-force ratio is determined by the following relationship: Je = (1--q2)Lee deltamue where q is the "degree of coupling" of electron transfer to proton translocation and Lee is the value of Je/delta-approximately similar e when there is no back pressure by formation of delta approximately muH+ (electrochemical potential difference of H+). The value of (1--q2) Lee increased with increasing pH in the neutral pH range. Uncouplers and ionophores that dissipate delta-approximately muH+ increased Je and decreased deltamue. The effects were more prominent in the lower pH range. Therefore, q must be smaller at higher pH. The coupling is probably tight when redox components are saturated with protons. The experimental results agreed with the theoretical predictions for a system where a hydrogen-translocating component functions as an electron-proton symport carrier.

Carbonyl Cyanide m-Chlorophenyl Hydrazone↗
PubMed1979

Flavocytochrome c of Chromatium vinosum. Some enzymatic properties and subunit structure.

The function and the structural features of Chromatium vinosum cytochrome c-552 have been investigated. Cytochrome c-552 has a sulfide-cytochrome c reductase activity and also catalyzes the reduction of elementary sulfur to sulfide with reduced benzylviologen as the electron donor. In the sulfide-cytochrome reduction, horse and yeast cytochromes c act as good electron acceptors, but cytochrome c' or cytochrome c-553(550) purified from the organism does not. The subunit structure of cytochrome c-552 has been studied. The cytochrome is split by 6 M urea into cytochrome and flavoprotein moieties with molecular weights of 21,000 and 46,000, respectively. The flavoprotein moiety is obtained by isoelectric focusing in the presence of 6 M urea and 0.1% beta-mercaptoethanol, while the hemoprotein moiety is obtained by gel filtration with Sephacryl S-200 in the presence of 6 M urea and 0.1 M KCl. Neither subunit has sulfide-cytochrome c reductase activity. Attempts to reconstitute the original flavocytochrome c from the subunits have been unsuccessful.

Amino Acids↗
PubMed1980

Near-infrared absorption spectra of light harvesting bacteriochlorophyll protein complexes from Chromatium vinosum.

Light harvesting (LH) bacteriochlorophyll (Bchl) protein complexes were isolated from chromatophores of Chromatium vinosum, by the combination of detergent solubilization, sodium dodecylsulfate (SDS) polyacrylamide gel electrophoresis (PAGE) and hydroxyapatite chromatography. Addition of the absorption spectra of these complexes reproduced the absorption spectrum of chromatophores from which these complexes were derived. This result led to the conclusion that these isolated complexes retained the near-infrared absorption spectra which these complexes showed as they existed in chromatophores. Two kinds of spectrally different chromatophores were obtained under different culture conditions. One of them contained two kinds of LH Bchl protein complexes; B890 containing and B850-B800 containing complexes, and the other contained, in addition, B820-B800 containing complex. B890 containing complexes from the two types of chromatophores were spectrally similar, whereas B850-B800 containing complexes were not the same with respect to the location of absorption maxima and the content of B850. It was shown that the variation of the near-infrared absorption spectra of the chromatophores is due to not only the variation of the ratio of complexes but also the variation of the absorption spectrum of a particular complex.

Bacterial Chromatophores↗
PubMed1981

Circular dichroism of bacteriochlorophyll a in light harvesting bacteriochlorophyll protein complexes from Chromatium vinosum.

Bacteriochlorophyll (Bchl) protein complexes containing light harvesting (LH) Bchls were isolated from Chromatium vinosum, and their CD spectra were measured in the near-infrared region. These isolated Bchl protein complexes retained the CD signals of LH Bchls that were observed in situ in chromatophores. The CD spectrum of fraction A (containing B890) consisted of paired positive and negative bands (a double CD) having a zero-crossing at 800 nm and a single negative band at around 900 nm attributed to the B890. For low 850 fraction B (B800 and B850), a double CD having a zero-crossing at 795 nm and a single negative band at around 850 nm attributed to the B850 were found. High 850 fraction B exhibited a double CD having a zero-crossing at 795 nm, a negative band at around 860 nm and a positive band at around 840 nm. For fraction C (B800 and B820), a double CD having a zero-crossing at 795 nm and a single negative band at around 830 nm, which was attributed to the B820, were found. The double CD was attributed to the B800 in fractions A, B, and C. There was no additional CD besides the CD of the isolated Bchl protein complexes in the CD spectra of chromatophores.

Bacterial Chromatophores↗
PubMed1990

Restoration of hydrogenase activity in hydrogenase-negative strains of Escherichia coli by cloned DNA fragments from Chromatium vinosum and Proteus vulgaris.

DNA fragments from Proteus vulgaris and Chromatium vinosum were isolated which restored hydrogenase activities in both hydA and hydB mutant strains of Escherichia coli. The hydA and hydB genes, which map near minute 59 of the genome map, 17 kb distant from each other, are not structural hydrogenase genes, but mutation in either of these genes leads to failure to synthesize any of the hydrogenase isoenzymes. The smallest DNA fragments which restored hydrogenase activity to both E. coli mutant strains were 4.7 kb from C. vinosum and 2.3 kb from P. vulgaris. These fragments were cleaved into smaller fragments which did not complement either of the E. coli mutations. The cloned heterologous genes also restored formate hydrogenlyase activity but they did not restore activity in hydE, hupA or hupB mutant strains of E. coli. The cloned genes, on plasmids, did not lead to the synthesis of proteins of sufficient size to be the hydrogenase catalytic subunit. The hydrogenase proteins synthesized by hydA and hydB mutant strains of E. coli transformed by cloned genes from P. vulgaris and C. vinosum were shown by isoelectric and immunological methods to be E. coli hydrogenase. Thus, these genes are not hydrogenase structural genes.

Blotting, Southern↗
PubMed1998

Sirohaem sulfite reductase and other proteins encoded by genes at the dsr locus of Chromatium vinosum are involved in the oxidation of intracellular sulfur.

The sequence of the dsr gene region of the phototrophic sulfur bacterium Chromatium vinosum D (DSMZ 180) was determined to clarify the in vivo role of 'reverse' sirohaem sulfite reductase. The dsrAB genes encoding dissimilatory sulfite reductase are part of a gene cluster, dsrABEFHCMK, that encodes four small, soluble proteins (DsrE, DsrF, DsrH and DsrC), a transmembrane protein (DsrM) with similarity to haem-b-binding polypeptides and a soluble protein (DsrK) resembling [4Fe-4S]-cluster-containing heterodisulfide reductase from methanogenic archaea. Northern hybridizations showed that expression of the dsr genes is increased by the presence of reduced sulfur compounds. The dsr genes are not only transcribed from a putative promoter upstream of dsrA but primary transcripts originating from (a) transcription start site(s) downstream of dsrB are also formed. Polar insertion mutations immediately upstream of dsrA, and in dsrB, dsrH and dsrM, led to an inability of the cells to oxidize intracellularly stored sulfur. The capability of the mutants to oxidize sulfide, thiosulfate and sulfite under photolithoautotrophic conditions was unaltered. Photoorganoheterotrophic growth was also unaffected. 'Reverse' sulfite reductase and DsrEFHCMK are, therefore, not essential for oxidation of sulfide or thiosulfate, but are obligatory for sulfur oxidation. These results, together with the finding that the sulfur globules of C. vinosum are located in the extracytoplasmic space whilst the dsr gene products appear to be either cytoplasmic or membrane-bound led to the proposal of new models for the pathway of sulfur oxidation in this phototrophic sulfur bacterium.

Amino Acid Sequence↗
PubMed1996

Insertional gene inactivation in a phototrophic sulphur bacterium: APS-reductase-deficient mutants of Chromatium vinosum.

In purple sulphur bacteria of the family Chromatiaceae sulphite oxidation via intermediary formation of adenylylsulphate is an enzymologically well characterized process. In contrast, the role of an alternative direct oxidation pathway via the enzyme sulphite:acceptor oxidoreductase has not been resolved. This paper reports the cloning of the genes encoding the adenylylsulphate-forming enzyme adenosine-5'-phosphosulphate (APS) reductase from Chromatium vinosum strain D (DSM 180'), a representative of the purple sulphur bacteria, and the construction of mutations in these genes by insertion of a kanamycin omega cartridge. The mutated genes were transferred to C. vinosum on suicide vectors of the pSUP series by conjugation and delivered to the chromosome by double homologous recombination. Southern hybridization and PCR analyses of the recombinants obtained verified the first insertional gene inactivation in purple sulphur bacteria. Enzymological studies demonstrated the absence of APS reductase from the mutants. Further phenotypic characterization showed no significant effect of APS reductase deficiency on the sulphite-oxidizing ability of the cells under photolithoautotrophic growth conditions. In the wild-type as well as in mutant strains, tungstate, the specific antagonist of molybdate, led to the intermediary accumulation of sulphite in the medium during sulphide oxidation and strongly inhibited growth with sulphite as photosynthetic electron donor; this indicates that a molybdoenzyme, probably sulphite:acceptor oxidoreductase, is the main sulphite-oxidizing enzyme in C. vinosum. Specific inactivation of selected genes as developed for C. vinosum in this study provides a powerful genetic tool for further analysis of sulphur metabolism and other metabolic pathways in phototrophic sulphur bacteria.

Chromatium↗
PubMed1999

Kinetics of photoacclimation in cultures of Chromatium vinosum DSM 185 during shifts in light irradiance.

Continuous cultures of Chromatium vinosum DSM 185 were shifted from a high to a low irradiance (67 to 4 microE m(-2) s(-1)) and vice versa (4 to 67 microE m(-2) s(-1)). The kinetics of photoacclimation of the cultures were analysed during these transitions until steady state was reached. When irradiance was shifted from 4 to 67 microE m(-2) s(-1), bacteriochlorophyll synthesis halted for 4 h. During this period, pigments were progressively diluted in the newly formed biomass, resulting in a lower specific pigment content. The specific growth rate of the organisms did not change immediately after the shift, but rather underwent a gradual increase during the following 10 h. This transition was accompanied by a transient increase in the levels of glycogen, indicating that CO2 fixation rates increased immediately after the shift, and that unused photosynthate was stored as glycogen. The shift from a high to a low irradiance was characterized by an immediate drop in the specific growth rate to virtually zero, and by comparatively sharp decreases in the specific rates of sulfur and sulfide oxidation and in the specific rate of glycogen accumulation. The specific content of bacteriochlorophyll a increased during the first 10 h. During the same period the specific content of glycogen decreased.

Adaptation, Physiological↗
PubMed2002

Crystallization and preliminary X-ray crystallographic analysis of glutathione amide reductase from Chromatium gracile.

The Chromatiaceae-specific glutathione amide reductase (GAR) belongs to the well known family of the glutathione reductases, even though differences in both substrate (glutathione amide instead of glutathione) and coenzyme (NADH instead of NADPH) specificities are reported. Crystals of the GAR enzyme from Chromatium gracile have been grown at 294 K by the hanging-drop vapour-diffusion method using lithium sulfate as a precipitant in the presence of nickel ions. The crystals belong to space group P4(1), with unit-cell parameters a = b = 71.93, c = 223.85 A, alpha = beta = gamma = 90 degrees and one dimer per asymmetric unit. A full set of X-ray diffraction data was collected to 2.1 A resolution with a completeness of 95.2%. Structure determination via the method of molecular replacement is under way.

Bacterial Proteins↗
PubMed1976

Isolation and characterization of the lipopolysaccharide of Chromatium vinosum.

Lipolysaccharide was isolated from Chromatium vinosum by phenol/water extraction. The lipopolysaccharide is found exclusively in the phenol phase and can be cleaved into a sugar moiety and a lipid A fraction by hydrolysis in 10% acetic acid at 100 degrees C for 3-4 h. The sugar moiety contains the neutral sugars 3-O-methyl-D-ribose, D-ribose, L-arabinose, mannosamine and glucose, and smaller quantities of D-rhamnose, D-glycero-D-manno-heptose (tentatively identified), quinovosamine and 2-keto-3-deoxyoctonate. L-glycero-D-manno-heptose was not detected. The 2-keto-3-deoxyoctonate linkage in C. vinosum lipopolysaccharide is more resistant to acid hydrolysis than that of Escherichia coli. The lipid A fraction contains glucosamine, mannose and the fatty acids of the lipopolysaccharide. The major fatty acid is beta-hydroxymyristic acid, with smaller amounts of lauric and palmitic acids as well as 14-carbon mono-unsaturated fatty acid, also being present. The phosphorus content of the C. vinosum lipopolysaccharide was found to be approximately 0.1%. Erythrocytes sensitized with alkali-treated C. vinosum lipopolysaccharide were agglutinated by antisera prepared against heat-killed cells. Untreated or heat-treated lipopolysaccharide did not sensitize erythrocytes. The lethal toxicity to mice of the C. vinosum lipopolysaccharide is about one-tenth as that from Salmonella abortus equi.

Animals↗
PubMed1977

Properties of ATPase activity in coupling factor from Chromatium strain D chromatophores.

Coupling factor extracted from chromatophores of the photosynthetic bacteria Chromatium strain D was partially purified. The enzyme catalyzed ATPase activity in the presence of Ca2+ and Mg2+ ions. Higher Vapp values were obtained when the activity was measured as a function of the divalent cation-ATP complex rather than as a function of either the divalent cation or ATP because the free components competitively inhibited the activity in the presence of the cation-ATP complex. The Km values were lower than or equal to the Ki values for free ATP indicating that the cation-ATP complex is bound tighter than the free ATP to the enzyme. Based on these results a possible mode of binding of substrate to the active site of the enzyme was suggested. A comparative study indicated no changes in the temperature dependance of ATPase activity when the enzyme was solubilized. However, possible conformation changes could have caused a decrease in the Km values for the (Ca-ATP)2- and (Mg-ATP)2- and in the Ki for free Mg2+ ions and ATP. The Ki for free Ca2+ ions increased on solubilization of the coupling factor. ATPase activity was inhibited by dicyclohexylcarbodiimide both in the soluble and in the membrane-bound coupling factor.

Adenosine Triphosphatases↗
PubMed1992

NOE and two-dimensional correlated 1H-NMR spectroscopy of cytochrome c' from Chromatium vinosum.

1H two-dimensional (nuclear Overhauser effect spectroscopy (NOESY) and two-dimensional correlated spectroscopy (COSY) spectra of cytochrome c' from Chromatium vinosum have been obtained. The protein is of medium size (Mr 28,000), essentially high spin (S = 5/2) although some quantum mechanical spin admixing with S = 3 2 may be present. Under these circumstances NOESY cross peaks have been revealed between geminal protons (alpha-CH2 propionate and beta-CH2 protons of the bound histidine) and between alpha-CH2 propionate protons and the heme methyl groups. COSY maps have confirmed the geminal nature of the proton pairs, even with a linewidth as large as 900 Hz; the J value is about 12 Hz. This assignment has rationalized on a sound basis the biochemical behavior of this protein with pH and has showed the utility of this kind of spectroscopy for the other cytochromes c' structures and analogous systems.

Chemical Phenomena↗