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PubMed1986

13C-NMR evidence of bacteriochlorophyll a formation by the C5 pathway in Chromatium.

The 13C-NMR spectra of bacteriochlorophyll a formed in the presence of L-[1-13C]glutamate and [2-13C]glycine in Chromatium vinosum strain D were analyzed. The isotope in the glutamate was specifically incorporated into eight carbon atoms in the tetrapyrrole macrocycle derived from the C-5 of 5-aminolevulinic acid (ALA), and the 13C in glycine was incorporated into the methyl carbon of the methoxycarbonyl group attached to the isocyclic ring of bacteriochlorophyll a. These labeling patterns provide evidence for the exclusive operation of the C5 pathway in ALA biosynthesis in the bacterium. The 13C chemical shifts of two quaternary carbons (C-9 and C-16) of bacteriochlorophyll a were reassigned in the present study.

Aminolevulinic Acid↗
PubMed1987

The nature of L8 and L8S8 forms of ribulose bisphosphate carboxylase/oxygenase from Chromatium vinosum.

L8 and L8S8 forms of ribulose bisphosphate carboxylase/oxygenase (RubisCO) have been prepared from Chromatium vinosum by the extremely mild method of centrifugal fractionation. Only the L8S8 form is detectable in crude extracts of this organism. Both forms show immunological identify in double diffusion studies using antibody to L subunits of the L8S8 form. L subunits from both L8 and L8S8 enzymes are identical by the criteria of peptides observed after limited proteolysis and N-terminal sequence analysis. In addition, these subunits show regions of homology with L subunits from Rhodospirillum rubrum, Anacystis nidulans, and spinach. S subunits of the C. vinosum enzyme are completely homologous to those from A. nidulans and higher plants from the 18th through 25th residue, a stretch preceded in all cases by two basic amino acids.

Amino Acid Sequence↗
PubMed1988

A homolog of ribulose bisphosphate carboxylase/oxygenase-binding protein in Chromatium vinosum.

A 700-kDa protein composed of 12 apparently identical 60-kDa subunits copurifies with the L8S8 form of ribulose bisphosphate carboxylase/oxygenase (RuBisCO) from Chromatium vinosum. Chromatography on DEAE-Sephadex A-50 separates the two proteins in pure form. On the basis of the highly reproducible copurification and reaction of the 700-kDa protein with antibodies to pea RuBisCO large (L)-subunit-binding protein, the protein from C. vinosum is designated as a putative binding protein (PBP) for RuBisCO. Also the N-terminal sequence of PBP is quite similar to that of both alpha and beta subunits of the L-subunit-binding protein. Our present research suggests that PBP may be a RuBisCO small-subunit-binding protein in C. vinosum. Measurements of RuBisCO activity and of species that immunologically cross react with RuBisCO or PBP (by enzyme-linked immunosorbent assay) establish that levels of the two proteins vary together in C. vinosum grown on different carbon sources.

Amino Acid Sequence↗
PubMed1988

Lysine and arginine transport in the photosynthetic bacterium Chromatium vinosum.

The photosynthetic purple sulfur bacterium Chromatium vinosum can take up both arginine and lysine in the light and, to a lesser extent, in the dark. Competitive inhibition experiments suggest the likely presence of two transport systems in this bacterium: One capable of transporting either lysine or arginine and a second capable of transporting arginine but not lysine. Uptake of both amino acids is electrogenic and appears to involve the cotransport of neither protons nor sodium ions. It is suggested that the transport occurs via an electrogenic uniport.

Arginine↗
PubMed1990

1H NMR studies of Chromatium vinosum cytochrome c'.

The cytochrome c' from Chromatium vinosum has been studied through 1H NMR in the pH range 4-11 in both the oxidized and the reduced forms. The 1H NMR spectra are similar to those of the other cytochrome c' systems. Three pKa values of 5.1, 7.0, and 9.2 have been observed for the oxidized species and tentatively assigned to the two carboxylate propionic residues of the heme moiety and to the iron-coordinated histidine 125, respectively. The spectra are consistent with an essentially S = 5/2 state in all the pH ranges investigated. Some evidence is provided for conformational flexibilities. Among the oxidized cytochromes c' the present one is capable of binding cyanide, giving rise to a low spin state. The reduced species is a typical high spin iron(II) system.

Chromatium↗
PubMed1992

Purification and characterization of chaperonin 10 from Chromatium vinosum.

Chromatium vinosum contains a polypeptide that is functionally and structurally similar to the Escherichia coli chaperonin 10. The protein has been purified to homogeneity by sucrose density gradient centrifugation followed by gel filtration using a Bio-Gel A-1.5 m column. The molecular mass of chaperonin 10, as determined by gel filtration or nondenaturing polyacrylamide gel electrophoresis, is 95 kDa. The oligomer is composed of seven or eight subunits. Comparisons of the overall amino acid composition and N-terminal sequences among chaperonin 10 species from C. vinosum and E. coli reflect a high degree of similarity. A physical association between chaperonins 60 and 10 from C. vinosum, in vitro, is supported by three experimental approaches. First, the proteins form a stable binary complex in sucrose density gradients, gel filtration chromatography, and nondenaturing polyacrylamide gel electrophoresis, solely in the presence of ATP and Mg2+. Second, chaperonin 10 from C. vinosum binds, selectively, to a chaperonin 60-coupled Affi-Gel 10 matrix column. Third, a slight molar excess of chaperonin 10 is able to abolish, almost completely, the ATPase in chaperonin 60. The rate for ATPase activity of chaperonin 60 from C. vinosum is enhanced when supplemented with monovalent cations.

Adenosine Triphosphatases↗
PubMed1975

A large photoreactive particle from Chromatium vinosum chromatophores.

Large photoreactive particles from Chromatium vinosum are obtained pure and in high yield by using a mixture of detergents at high ionic strength to dissociate the chromatophore membrane. The particles contain all of the secondary electron acceptor of the chromatophores and about half of the cytochrome. Their content of ubiquinone is greatly enridhed as compared with chromatophores. Th individual particles have an estimated molecular weight of between 650,000 and 810,000. Gel electrophoresis of the preparation in sodium dodecylsulfate shows polypeptides with molecular weights of 50-45,000, 30,000, 27,000, 22,000 and 12,000. The 50-45,000 components are cytochromes. The 30,000, 27,000 and 22,000 components may be analogous to the triad of polypeptides present in Rhodopseudomonas spheroides reaction centers. The non-cytochrome components are partly soluble in chloroform/methanol. Aggregates of particles appear in these preparations. Electron microscopy of the aggregates demonstrates rectilinear lattices of isodiametric particles, 120 A in diameter. These sheet-like structures are one unit thick and typically contain 9-16 members. They appear to arise by aggregation during isolation but are probably similar to native aggregates apparent within chromatophores after treatment with detergents at low salt concentration.

Bacterial Chromatophores↗
PubMed1975

The iron electron-nuclear double resonance (ENDOR) of 4-Fe clusters in iron-sulfur proteins from Chromatium and Clostridium pasteurianum.

Iron electron-nuclear double resonance (ENDOR) measurements were made of the 4-Fe clusters in oxidized Chromatium high-potential iron-sulfur protein, dithionite-reduced high-potential iron-sulfur protein in 80% dimethylsulphoxide, fully reduced Clostridium pasteurianum ferredoxin in aqueous solution and in 80% dimethylsulfoxide. The hyperfine couplings determined show that: i) the electron distribution in each case is nearly symmetric; ii) there are two types of iron in oxidized high potential iron-sulfur protein; iii) only one type of iron is observed in each fully reduced 4-Fe cluster; iv) the data also suggest a greater electron delocalization onto the ligands as compared to the 2-Fe ferredoxins.

Bacterial Proteins↗
PubMed1976

The primary photoreactions in the complex cytochrome-P-890-P-760 (bacteriopheophytin760) of Chromatium minutissimum at low redox potentials.

Experimental evidence for electron transfer, photosensitized by bacteriochlorophyll, from cytochrome c to a pigment complex P-760 (involving bacteriopheophytin-760 and also bacteriochlorophyll-800) in the reaction centers of Chromatium minutissimum has been described. This photoreaction occurs between 77 and 293 degrees K at a redox potential of the medium between -250 and -530 mV. Photoreduction of P-760 is accompanied by development of a wide absorption band at 650 nm and of an EPR signal with g=2.0025+/-0.0005 and linewidth of 12.5+/-0.5 G, which are characteristic of the pigment radical anion. It is suggested that the photoreduction of P-760 occurs under the interaction of reduced cytochrome c with the reaction center state P+-890-P--760 which is induced by light. The existence of short-lived state P+-890-P--760 is indicated by the recombination luminescence with activation energy of 0.12 eV and t 1/2 less than or equal to 6 ns. This luminescence is exicted and emitted by bacteriochlorophyll and disappears when P-760 is reduced. At low redox potentials, the flash-induced absorbance changes related to the formation of the carotenoid triplet state with t 1/2 = 6 mus at 20 degreesC are observed. This state is not formed when P-760 is reduced at 293 and 160 degrees K. It is assumed that this state is formed from the reaction center state P+-890---760, which appears to be a primary product of light reaction in the bacterial reaction centers and which is probably identical with the state PF described in recent works.

Chromatium↗
PubMed1976

EPR and optical spectroscopic properties of the electron carrier intermediate between the reaction center bacteriochlorophylls and the primary acceptor in Chromatium vinosum.

1. A reaction center-cytochrome c complex has been isolated from Chromatium vinosum which is capable of normal photochemistry and light-activated rapid cytochrome c553 and c555 oxidation, but which has no antenna bacteriochlorophyll. As is found in whole cells, ferrocytochrome c553 is oxidized irreversibly in milliseconds by light at 7 K. 2. Room temperature redox potentiometry in combination with EPR analysis at 7 K, of cytochrome c553 and the reaction center bacteriochlorophyll dimer (BChl)2 absorbing at 883 nm yields identical results to those previously reported using optical analytical techniques at 77 K. It shows directly that two cytochrome c553 hemes are equivalent with respect to the light induced (BChl)2+. At 7 K, only one heme can be rapidly oxidized in the light, commensurate with the electron capacity of the primary acceptor (quinone-iron) being unity. 3. Prior chemical reduction of the quinone-iron followed by illumination at 200K, however, leads to the slow (t1/2 approximately equal to 30 s) oxidation of one cytochrome c553 heme, with what appears to be concommitant reduction of one of the two bacteriophytins (BPh) of the reaction center as shown by bleaching of the 760 nm band, a broad absorbance increase at approx. 650 nm and a bleaching at 543 nm. The 800 nm absorbing bacteriochlorophyll is also involved since there is also bleaching at 595 and 800 nm; at the latter wave-length the remaining unbleached band appears to shift significantly to the blue. No redox changes in the 883 absorbing bacteriochlorophyll dimer are seen during or after illumination under these conditions. The reduced part of the state represents what is considered to be the reduced form of the electron carrier (I) which acts as an intermediate between the bacteriochlorophyll dimer and quinone-iron. The state (oxidized c553/reduced I) relaxes in the dark at 200K in t1/2 approx. 20 min but below 77 K it is trapped on a days time scale. 4. EPR analysis of the state trapped as described above reveals that one heme equivalent of cytochrome becomes oxidized for the generation of the state, a result in agreement with the optical data. Two prominent signals are associated with the trapped state in the g = 2 region, which can be easily resolved with temperature and microwave power saturation: one has a line width of 15 g and is centered at g = 2.003; the other, which is the major signal, is also a radical centered at g = 2.003 but is split by 60 G and behaves as though it were an organic free-radical spin-coupled with another paramagnetic center absorbing at higher magnetic field values; this high field partner could be the iron-quinone of the primary acceptor. The identity of two signals associated with I-. is consistent with the idea that the reduced intermediary carrier is not simply BPh-. but also involves a second radical, perhaps the 800 nm bacteriochlorophylls in the reduced state...

Bacterial Chromatophores↗
PubMed1977

Delayed fluorescence from bacteriochlorophyll in Chromatium vinosum chromatophores.

Delayed fluorescence from bacteriochlorophyll in Chromatium vinosum chromatophores was studied at room temperature and under intermittent illuminations. The decay of delayed fluorescence was constituted of two components; a fast component decayed with a half time of about 8 ms, a slow one decayed in parallel with the reduction of photooxidized bacteriochlorophyll (P+) with a half time of 100-200 ms. The biphasic decay of delayed fluorescence indicated that a rapid equilibrium was established between the primary electron acceptor and the secondary acceptor. In the presence of o-phenanthroline, the time course of the decay of delayed fluorescence was identical with that of the reduction of P+ in reaction center-rich subchromatophore particles, although they did not necessarily coincide with each other in "intact" chromatophores. The intensity of the slow component was increased and the decay was accelerated at basic pH values. Reagents that dissipate the proton gradient across the chromatophore membranes such as carbonylcyanide m-chlorophenylhydrazone (CCCP) and nigericin accelerated the decay of the slow component. These effects are probably resulting from changes in internal pH of chromatophore vesicles. Reagents that dissipate the membrane potential such as CCCP and valinomycin decreased the intensity.

Bacterial Chromatophores↗
PubMed1978

The effects of uncoupler on the rates of cytochrome oxidation and reduction in the photosynthetic bacterium, Chromatium. Evidence for a possible cytochrome switching.

The uncoupler, m-chlorocarbonyl cyanide phenylhydrazone (CCCP) added to anerobic, dark-adapted whole cells of Chromatium vinosum is found to speed the reduction of cytochrome after oxidation by laser or by steady illumination and, subject to unknown factors, to slow the laser-induced oxidation. There is considerable evidence, including spectra and loss of low-temperature oxidizability that this results from a switch of the identity of the cytochrome oxidized from the low-potential cytochrome c-552 to the high-potential cytochrome c555. Redox control and/or control by conformational movements of the cytochromes, either being coupled to energy transduction in the cyclic system, are suggested as mechanisms for the switching. If the switching hypothesis is not accepted, the increased rate of reduction could alternatively be explained by postulating a phosphorylation site in the reduction pathway.

Carbonyl Cyanide m-Chlorophenyl Hydrazone↗
PubMed1978

Structural organization of the Chromatium vinosum reaction center associated c-cytochromes.

Magnetic interactions operating between the Chromatium vinosum reaction center associated c-cytochromes and the electron carriers of the reaction center have been assayed by comparing the magnetic properties of these components alone, and in various combinations with paramagnetic forms of the reaction center electron carriers. These studies have yielded the following results. 1. The oxidized paramagnetic forms of the high potential cytochromes c-555 produce no discernable alteration of the light-induced (BChl)2.+signal. 2. Similarly, analysis of the lineshape of the light-induced (BChl)2.+signal shows that a magnetic interaction with the oxidized low potential cytochromes c-553 is likely to produce less than a 1 gauss splitting of the (BChl)2.+signal, which corresponds to a minimum separation of 25 +/- 3 A between the unpaired spins if the heme and (BChl)2 are orientated in a coplanar arrangement, suggesting a minimum separation of 15+/- 3A between the heme edge and the (BChl)2 edge. 3. a prominent magnetic interaction is observed to operate between the cytochrome c-553 and c-555, which results in a 30-35 gauss splitting of these spectra, and suggests an iron to iron separation of about 8 A.4. Magnetic interactions are not observed between the c-cytochromes and the reaction center "primary acceptor" (the iron . quinone complex) nor with the reaction center intermediate electron carrier (which involves bacteriopheophytin) suggesting separations greater than 10 A. 5. Magnetic interactions are not discerned between the two cytochrome c-553 hemes, nor between the two cytochrome c-555 hemes, implying that the distance between the cytochromes of the same pair is greater than 10 A. 6. EPR studies of oriented chromatophores have demonstrated that the cytochrome c-553 and c-555 hemes are perpendicular to each other, and suggest that the cytochrome c-553 heme plane lies parallel to the plane of the membrane, while the cytochrome c-555 heme plane lies perpendicular to the plane of the membrane surface.

Bacterial Chromatophores↗
PubMed1980

Study of electrogenic electron transfer steps in chromatophore membrane of Chromatium vinosum by the response of merocyanin dye.

1. Electrogenic steps in photosynthetic cyclic electron transport in chromatophore membrane of Chromatium vinosum were studied by measuring absorption changes of added merocyanin dye and of intrinsic carotenoid. 2. The change in dye absorbance was linear with the membrane potential change induced either by light excitation or by application of diffusion potential by adding valinomycin in the presence of K+ concentration gradient. 3. It was estimated that chromatophore membrane became 40--60 mV and 110--170 mV inside positive upon single and multiple excitations with single-turnover flashes, respectively, from the responses of the dye and the carotenoid. 4. Electron transfers between cytochrome c-555 or c-552 and reaction center bacteriochlorophyll dimer (BChl2) and between BChl2 and the primary electron acceptor were concluded to be electrogenic from the redox titration of the dye response. 5. No dye response which corresponded to the change of redox level of cytochrome b was observed in the titration curve. Addition of antimycin A slightly decreased the dye response. 6. The dye response was decreased under phosphorylating conditions. 7. From the results obtained localization of the electron transfer components in chromatophore membrane is discussed.

Antimycin A↗
PubMed1980

The role of histidine-42 in the oxidation-reduction mechanism of Chromatium vinosum high potential iron-sulfur protein.

The second order rate constants for the oxidation of high potential iron-sulfur protein (Hipip) of Chromatium vinosum by ferricyanide were determined as a function of ionic strength and pH. From the ionic strength results, calculations were done to correct the rate constant at each pH for the electrostatic interactions between Hipip and ferricyanide. The electrostatic corrections are necessary since the charge of the protein changes as a function of pH and can mask the ionization of mechanistically important amino acid residues. An apparent pKa congruent to 7 was obtained from electrostatically corrected rate-pH profile, indicating the possible participation of histidine. Perturbation difference spectroscopic studies of Hipip as a function of pH also gave apparent pKa values of 6.9 and 6.7 for the reduced and oxidized protein, respectively. That it was indeed His 42 (the only His in the polypeptide) that was responsible for the kinetic and spectroscopic pKa values was demonstrated by modification of His 42 of Hipip by the histidine selective reagent diethylpyrocarbonate. No modification of Tyr 19 could be detected. It is concluded that either deprotonation or modification of His 42 results in the destabilization of the reduced cluster and thus a faster rate of oxidation. This work provides the first experimental evidence of the 'squeeze effect' mechanism (Carter, C.W., Jr., Kraut, J., Freer, S.T. and Alden, R.A. (1974) J. Biol. Chem. 249, 6339--6346) in which the polypeptide directly modulates the stability of the iron-sulfur cluster.

Chromatium↗
PubMed1980

The photosynthetic electron transfer chain of Chromatium vinosum chromatophores: flash-induced cytochrome b reduction.

Reduction of a cytochrome b following excitation by a single, short, near-saturating light flash has been demonstrated in Chromatium vinosum chromatophores. The extent of reduction is increased by addition of antimycin. The cytochrome has an alpha-band maximum at 562 nm in the presence of antimycin. The cytochrome b reduction is most readily observed in the presence of antimycin at high redox potential when cytochrome c-555 is oxidised before excitation. Under these conditions the half-time for reduction is about 20 ms, and the extent is about 0.5 mol of cytochrome b reduced per mol of reaction center oxidised. This extent of reduction is observed on the first flash-excitation from the dark-adapted state, and there was no indication that the reaction center quinone acceptor complex acted as a two-electron accumulating system. With cytochrome c-555 reduced before excitation, the extent of cytochrome b reduction is approximately halved. The factors which result in substoichiometric cytochrome b reduction are not yet understood. Agents which appear to inhibit primary acceptor oxidation by the secondary acceptor (UHDBT, PHDBT, DDAQQ, HOQNO, o-phenanthroline), inhibit reduction of the cytochrome b. DBMIB inhibits cytochrome b reduction but does not appear to inhibit primary acceptor oxidation. These observations confirm that a cytochrome b receives electrons delivered from the primary acceptor complex, and indicate that the photoreduced cytochrome b is reoxidised via an antimycin-sensitive pathway.

Antimycin A↗
PubMed1980

Effects of surface potential and membrane potential on the midpoint potential of cytochrome c-555 bound to the chromatophore membrane of Chromatium vinosum.

The values of midpoint potential (Em) of cytochrome c-555 bound to the chromatophore membranes of a photosynthetic bacterium Chromatium vinosum was determined under various pH and salt conditions. After a long incubation at high ionic concentrations in the presence of carbonylcyanide m-chlorophenylhydrazone, which was added to abolish electrical potential difference between the inner and outer bulk phases of chromatophore, the Em value was almost constant at pH values between 4.0 and 8.4. With the decrease of salt concentration, the pH dependence of the Em value became more marked. Under low ionic conditions, Em became more positive with the decrease of pH. Addition of salt made the value more positive or negative at pH values higher or lower than 4.5, respectively. Divalent cation salts were more effective than monovalent cation salts in producing the positive shift of Em at pH 7.8. The Em value became more positive when the electrical potential of the inner side of the chromatophore was made more positive by the diffusion potential induced by the K+ concentration gradient in the presence of valinomycin. These results were explained by a change of redox potential at the inner surface of the chromatophore membrane, at which the cytochrome is assumed to be situated, due to the electrical potential difference with respect to the outer solution induced by the surface potential or membrane potential change. The values for the surface potential and the net surface charge density of the inner surface of the chromatophore membrane were estimated using the Gouy-Chapman diffuse double layer theory.

Bacterial Chromatophores↗
PubMed1986

The use of a water-soluble carbodiimide to study the interaction between Chromatium vinosum flavocytochrome c-552 and cytochrome c.

The interaction between horse heart cytochrome c and Chromatium vinosum flavocytochrome c-552 was studied using the water-soluble reagent 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC). Treatment of flavocytochrome c-552 with EDC was found to inhibit the sulfide: cytochrome c reductase activity of the enzyme. SDS gel electrophoresis studies revealed that EDC treatment led to modification of carboxyl groups in both the Mr 21 000 heme peptide and the Mr 46 000 flavin peptide, and also to the formation of a cross-linked heme peptide dimer with an Mr value of 42 000. Both the inhibition of sulfide: cytochrome c reductase activity and the formation of the heme peptide dimer were decreased when the EDC modification was carried out in the presence of cytochrome c. In addition, two new cross-linked species with Mr values of 34 000 and 59 000 were formed. These were identified as cross-linked cytochrome c-heme peptide and cytochrome c-flavin peptide species, respectively. Neither of these species were formed in the presence of a cytochrome c derivative in which all of the lysine amino groups had been dimethylated, demonstrating that EDC had cross-linked lysine amino groups on native cytochrome c to carboxyl groups on the heme and flavin peptides. A complex between cytochrome c and flavocytochrome c-552 was required for cross-linking to occur, since ionic strengths above 100 mM inhibited cross-linking.

Animals↗