Isolation and identification of granule-associated proteins relevant for poly(3-hydroxyalkanoic acid) biosynthesis in Chromatium vinosum D

Abstract Poly(3-hydroxybutyric acid) granules, which harbored only four major granule-associated proteins as revealed by SDS polyacrylamide gel electrophoresis, were isolated from crude cellular extracts of Chromatium vinosum D by centrifugation in a linear sucrose gradient. N-Terminal amino acid sequence determination identified two proteins of M _r 41 000 and M _{r 40 000} as the phaE _Cv and phaC _Cv translational products, respectively, of C. vinosum D. In a previous study it was shown that both proteins are required for the expression opf poly(3-hydroxyalkanoic acid) synthase activity. The N-terminus of the third protein ( M _r 17 000) exhibited no homology to other proteins. Lysozyme, which was during purification of the granules, exhibited a strong affinity to PHB granules and was identified as the fourth protein enriched with the granules.     

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 α-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.     

The role of soluble cytochrome c-551 in cyclic electron flow-driven active transport in Chromatium vinosum

Spheroplasts have been prepared from the photosynthetic purple sulfur bacterium Chromatium vinosum by lysozyme plus ethylenediaminetetraacetic acid treatment. These spheroplasts are able to take up alanine in the light, but light-dependent alanine uptake is lost upon subsequent washing of the spheroplasts. The observations that alanine uptake driven by a potassium plus valinomycin-induced membrane potential (outside positive) is not affected by washing and that light-dependent alanine uptake can be restored by addition of the supernatant from washing suggest that a soluble electron carrier is lost during washing. Light-dependent alanine uptake in washed spheroplasts could be restored by addition of C. vinosum cytochrome c-551. Other soluble electron carriers from C. vinosum (high-potential iron protein, cytochrome ‘f’, cytochrome c′ and the flavocytochrome c-552) did not restore alanine uptake nor did a variety of other soluble electron carrier proteins from other organisms. These results suggest that cytochrome c-551 functions as an electron carrier in the cyclic electron transfer chain of C. vinosum. Mitochondrial cytochrome c (equine heart) and cytochrome c-551 from Pseudomonas aeruginosa were highly effective in restoring light-dependent alanine uptake in washed spheroplasts, making it likely that C. vinosum cytochrome c-551 is related by evolution to the same cytochrome c family as these other two c cytochromes.     

Stabilization of mesophilic Allochromatium vinosum cytochrome c′ through specific mutations modeled by a thermophilic homologue

AVCP cytochrome c′ from mesophilic Allochromatium vinosum exhibits lower stability than a thermophilic counterpart, Hydrogenophilus thermoluteolus cytochrome c′ (PHCP), in which the six specific amino acid residues that are not conserved in AVCP are responsible for its stability. Here we measured the stability of AVCP variants carrying these specific residues instead of the original AVCP ones. Among the six single AVCP variants, all of which formed a dimeric structure similar to that of the wild-type, three were successfully stabilized compared with the wild-type, while one showed lower stability than the wild-type. In addition, the most stabilized and destabilized AVCP variants could bind CO, similar to the wild-type. These results indicated that mesophilic AVCP could be stabilized through specific three mutations modeled by the thermophilic counterpart, PHCP, without changing the CO binding ability.     

Molecular genetic evidence for extracytoplasmic localization of sulfur globules in Chromatium vinosum

Purple sulfur bacteria store sulfur as intracellular globules enclosed by a protein envelope. We cloned the genes sgpA, sgpB, and sgpC, which encode the three different proteins that constitute the sulfur globule envelope of Chromatium vinosum D (DSMZ 180^T). Southern hybridization analyses and nucleotide sequencing showed that these three genes are not clustered in the same operon. All three genes are preceded by sequences resembling σ⁷⁰-dependent promoters, and hairpin structures typical for rho-independent terminators are found immediately downstream of the translational stop codons of sgpA, sgpB, and sgpC. Insertional inactivation of sgpA in Chr. vinosum showed that the presence of only one of the homologous proteins SgpA and SgpB suffices for formation of intact sulfur globules. All three sgp genes encode translation products which – when compared to the isolated proteins – carry amino-terminal extensions. These extensions meet all requirements for typical signal peptides indicating an extracytoplasmic localization of the sulfur globule proteins. A fusion of the phoA gene to the sequence encoding the proposed signal peptide of sgpA led to high specific alkaline phosphatase activities in Escherichia coli, further supporting the envisaged targeting process. Together with electron microscopic evidence these results provide strong indication for an extracytoplasmic localization of the sulfur globules in Chr. vinosum and probably in other Chromatiaceae. Extracytoplasmic formation of stored sulfur could contribute to the transmembranous Δp that drives ATP synthesis and reverse electron flow in Chr. vinosum. Received: 1 October 1997 / Accepted: 17 December 1997     

Sulfide oxidation in the phototrophic sulfur bacterium Chromatium vinosum

Sulfide oxidation in the phototrophic purple sulfur bacterium Chromatium vinosum D (DSMZ 180^T) was studied by insertional inactivation of the fccAB genes, which encode flavocytochrome c, a protein that exhibits sulfide dehydrogenase activity in vitro. Flavocytochrome c is located in the periplasmic space as shown by a PhoA fusion to the signal peptide of the hemoprotein subunit. The genotype of the flavocytochrome-c-deficient Chr. vinosum strain FD1 was verified by Southern hybridization and PCR, and the absence of flavocytochrome c in the mutant was proven at the protein level. The oxidation of thiosulfate and intracellular sulfur by the flavocytochrome-c-deficient mutant was comparable to that of the wild-type. Disruption of the fccAB genes did not have any significant effect on the sulfide-oxidizing ability of the cells, showing that flavocytochrome c is not essential for oxidation of sulfide to intracellular sulfur and indicating the presence of a distinct sulfide-oxidizing system. In accordance with these results, Chr. vinosum extracts catalyzed electron transfer from sulfide to externally added duroquinone, indicating the presence of the enzyme sulfide:quinone oxidoreductase (EC 1.8.5.-). Further investigations showed that the sulfide:quinone oxidoreductase activity was sensitive to heat and to quinone analogue inhibitors. The enzyme is strictly membrane-bound and is constitutively expressed. The presence of sulfide:quinone oxidoreductase points to a connection of sulfide oxidation to the membrane electron transport system at the level of the quinone pool in Chr. vinosum. Received: 5 November 1997 / Accepted: 30 March 1998     

Experimental evidence for the role of buried polar groups in determining the reduction potential of metalloproteins: the S79P variant of Chromatium vinosum HiPIP

 The amide group between residues 78 and 79 of Chromatium vinosum high-potential iron-sulfur protein (HiPIP) is in close proximity to the Fe₄S₄ cluster of this protein and interacts via a hydrogen bond with Sγ of Cys77, one of the cluster ligands. The reduction potential of the S79P variant was 104±3 mV lower than that of the recombinant wild-type (rcWT) HiPIP (5 mM phosphate, 100 mM NaCl, pH 7, 293 K), principally due to a decrease in the enthalpic term which favors the reduction of the rcWT protein. Analysis of the variant protein by NMR spectroscopy indicated that the substitution has little effect on the structure of the HiPIP or on the electron distribution in the oxidized cluster. Potential energy calculations indicate that the difference in reduction potential between rcWT and S79P variant HiPIPs is due to the different electrostatic properties of amide 79 in these two proteins. These results suggest that the influence of amide group 79 on the reduction potential of C. vinosum HiPIP is a manifestation of a general electrostatic effect rather than a specific interaction. More generally, these results provide experimental evidence for the importance of buried polar groups in determining the reduction potentials of metalloproteins. Received: 26 April 1999 / Accepted: 24 August 1999     

酒色着色菌利用产酸克雷伯氏菌发酵废液产氢

研究了酒色着色菌(Chromatiumvinosum DSM185)利用产酸克雷伯氏菌(Klebsiellaoxytoca HP1)发酵产氢废液进行光发酵和暗发酵产氢的可行性,以达到对产氢底物的充分利用和对产氢废液的进一步处理。研究结果表明C.vinosum可以利用K.oxytoca的发酵废液进行光发酵产氢和暗发酵产氢。C.vinosum发酵产氢后废液中残余还原糖和主要有机酸(丁酸)的含量明显降低,发酵产氢的最佳pH为6.5,添加0.1%(W/W)NH4Cl能促进产氢。在光照条件下丁酸利用率可达54.38%,产氢量达36.97mL/mg;在黑暗条件下丁酸利用率可达36.01%,产氢量达37.50mL/mg。     

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.     

Ein Beitrag zur Systematik und Entwicklungsbiologie höherer Pilze: Hefe-Typen der Basidiomyceten. Teil II: Microbotryum-Typ

In this and three further papers 205 yeasts and yeast states of Basidiomycetes and presumed relatives were investigated comparatively on the basis of the carbohydrate (neutral sugars) pattern of purified cell walls, urease-activity, diazonium blue B reaction on the production of extracellular amyloid compounds (EAS), fermentation of carbohydrates, and ubiquinone data. A clustering leading to the Protomyces-, the Microbotryum-, the Ustilago-, the Dacrymyces-, and the Tremella-type became apparent, especially from the qualitative and quantitative cell wall carbohydrate pattern. The different yeast types correspond well with 5S rRNA clusters known from the literature. 31 strains clustering within the Microbotryum-type comprise the phragmobasidial smut fungi of dicotyledonous hosts (Microbotryum. Sphacelotheca), the phragmobasidial Rhodosporidium- and Leucosporidium-species including some anamorph Rhodotorula-species, which lack an oxidative degradation of myo-inositol, the genera Sporobolomyces and Sporidiobolus, the Septobasidiales and some simple septate Auriculariales e.g. Agaricostilbum, Platygloea. Main characteristics of the Microbotryum-type are: 1. The absence of extracellular amyloid compounds. 2. The dominance of mannose and the presence of fucose as cell wall constituents. 3. A positive DBB-reaction and splitting of urea. Four Ustilago species parasitic on dicotyledonous hosts were transfered to Microbotryum (M. scabiosae, M. scorzonerae, M. cordae, M. vinosum) as a consequence from cell wall carbohydrate composition, production of rhodotorulic acid, and 5S rRNA sequence data from the literature. The predominance of mannose in the cell wall — otherwise only known from ascomycetous yeasts –, a type A secondary structure of 5S rRNA, a simple unifactorial mating system in all parasitic smut species suggest that the Microbotryum-type might be ancestral to the Ustilago-type. An evolution of simple (“siphonal”) holobasidia from “pseudotrichal” phragmobasidia will be discussed.