Publications

• Reaction cycle of the dissimilatory sulfite reductase from Archaeoglobus fulgidus.

  Parey K., Warkentin E., Kroneck P.M., Ermler U.

  A vital process in the biogeochemical sulfur cycle is the dissimilatory sulfate reduction pathway in which sulfate (SO₄⁻²) is converted to hydrogen sulfide (H₂S). Dissimilatory sulfite reductase (dSir), its key enzyme, hosts a unique siroheme-[4Fe-4S] cofactor and catalyzes the six-electron reduct ... >> More

  A vital process in the biogeochemical sulfur cycle is the dissimilatory sulfate reduction pathway in which sulfate (SO₄⁻²) is converted to hydrogen sulfide (H₂S). Dissimilatory sulfite reductase (dSir), its key enzyme, hosts a unique siroheme-[4Fe-4S] cofactor and catalyzes the six-electron reduction of sulfite (SO₃²⁻) to H₂S. To explore this reaction, we determined the X-ray structures of dSir from the archaeon Archaeoglobus fulgidus in complex with sulfite, sulfide (S²⁻) carbon monoxide (CO), cyanide (CN⁻), nitrite (NO₂⁻), nitrate (NO₃⁻), and phosphate (PO₄³⁻). Activity measurements indicated that dSir of A. fulgidus reduces, besides sulfite and nitrite, thiosulfate (S₂O₃²⁻) and trithionate (S₃O₆²⁻) and produces the latter two compounds besides sulfide. On this basis, a three-step mechanism was proposed, each step consisting of a two-electron transfer, a two-proton uptake, and a dehydration event. In comparison, the related active site structures of the assimilatory sulfite reductase (aSir)- and dSir-SO₃²⁻complexes reveal different conformations of Argα170 and Lysα211 both interacting with the sulfite oxygens (its sulfur atom coordinates the siroheme iron), a sulfite rotation of ~60° relative to each other, and different access of solvent molecules to the sulfite oxygens from the active site cleft. Therefore, solely in dSir a further sulfite molecule can be placed in van der Waals contact with the siroheme-ligated sulfite or sulfur-oxygen intermediates necessary for forming thiosulfate and trithionate. Although reported for dSir from several sulfate-reducing bacteria, the in vivo relevance of their formation is questionable. << Less

  Biochemistry 49:8912-8921(2010) [PubMed] [EuropePMC]

• Dissimilatory sulphite reductase from Archaeoglobus fulgidus: physico-chemical properties of the enzyme and cloning, sequencing and analysis of the reductase genes.

  Dahl C., Kredich N.M., Deutzmann R., Trueper H.G.

  A dissimilatory sulphite reductase was isolated from the extremely thermophilic dissimilatory sulphate-reducing archaeon Archaeoglobus fulgidus. In common with other dissimilatory sulphite reductases thus far characterized, the enzyme has an alpha 2 beta 2-structure and contains sirohaem, non-haem ... >> More

  A dissimilatory sulphite reductase was isolated from the extremely thermophilic dissimilatory sulphate-reducing archaeon Archaeoglobus fulgidus. In common with other dissimilatory sulphite reductases thus far characterized, the enzyme has an alpha 2 beta 2-structure and contains sirohaem, non-haem iron atoms and acid labile sulphide. The oxidized enzyme exhibited absorption maxima at 281, 394, 545 and 593 nm with a weak band around 715 nm. We have cloned and sequenced the genes for the alpha and beta subunits of this enzyme, which we designate dsrA and dsrB, respectively. They are contiguous in the order dsrA dsrB and probably comprise an operon, since dsrA is preceded by sequences characteristic of promoters in methanogenic archaea, and dsrB is followed by a sequence resembling termination signals in extremely thermophilic sulphur-dependent archaea. dsrA and dsrB encode 47.4 kDa and 41.7 kDa peptides, which have 25.6% amino acid sequence identity, indicating that they may have arisen by duplication of an ancestral gene. Each deduced peptide contains cysteine clusters resembling those postulated to bind sirohaem-[Fe4S4] complexes in sulphite reductases and nitrite reductases from other species. The dsrB encoded peptide lacks a single cysteine residue in one of the two clusters, suggesting that only the alpha subunit binds a sirohaem-[Fe4S4] complex, and chemical analyses showed the presence of only two sirohaems per alpha 2 beta 2 enzyme molecule. Both deduced peptides also contain an arrangement of cysteine residues characteristic of [Fe4S4] ferredoxins, and chemical analyses were consistent with the presence of six [Fe4S4] clusters per alpha 2 beta 2 enzyme molecule, two of which would be expected to be associated with sirohaem while the other four could bind to the ferredoxin-like sites. << Less

  J. Gen. Microbiol. 139:1817-1828(1993) [PubMed] [EuropePMC]

• The crystal structure of Desulfovibrio vulgaris dissimilatory sulfite reductase bound to DsrC provides novel insights into the mechanism of sulfate respiration.

  Oliveira T.F., Vonrhein C., Matias P.M., Venceslau S.S., Pereira I.A.C., Archer M.

  Sulfate reduction is one of the earliest types of energy metabolism used by ancestral organisms to sustain life. Despite extensive studies, many questions remain about the way respiratory sulfate reduction is associated with energy conservation. A crucial enzyme in this process is the dissimilator ... >> More

  Sulfate reduction is one of the earliest types of energy metabolism used by ancestral organisms to sustain life. Despite extensive studies, many questions remain about the way respiratory sulfate reduction is associated with energy conservation. A crucial enzyme in this process is the dissimilatory sulfite reductase (dSiR), which contains a unique siroheme-[4Fe4S] coupled cofactor. Here, we report the structure of desulfoviridin from Desulfovibrio vulgaris, in which the dSiR DsrAB (sulfite reductase) subunits are bound to the DsrC protein. The alpha(2)beta(2)gamma(2) assembly contains two siroheme-[4Fe4S] cofactors bound by DsrB, two sirohydrochlorins and two [4Fe4S] centers bound by DsrA, and another four [4Fe4S] centers in the ferredoxin domains. A sulfite molecule, coordinating the siroheme, is found at the active site. The DsrC protein is bound in a cleft between DsrA and DsrB with its conserved C-terminal cysteine reaching the distal side of the siroheme. We propose a novel mechanism for the process of sulfite reduction involving DsrAB, DsrC, and the DsrMKJOP membrane complex (a membrane complex with putative disulfide/thiol reductase activity), in which two of the six electrons for reduction of sulfite derive from the membrane quinone pool. These results show that DsrC is involved in sulfite reduction, which changes the mechanism of sulfate respiration. This has important implications for models used to date ancient sulfur metabolism based on sulfur isotope fractionations. << Less

  J. Biol. Chem. 283:34141-34149(2008) [PubMed] [EuropePMC]

  This publication is cited by 5 other entries.

• The "bacterial heterodisulfide" DsrC is a key protein in dissimilatory sulfur metabolism.

  Venceslau S.S., Stockdreher Y., Dahl C., Pereira I.A.

  DsrC is a small protein present in organisms that dissimilate sulfur compounds, working as a physiological partner of the DsrAB sulfite reductase. DsrC contains two redox active cysteines in a flexible carboxy-terminal arm that are involved in the process of sulfite reduction or sulfur(1) compound ... >> More

  DsrC is a small protein present in organisms that dissimilate sulfur compounds, working as a physiological partner of the DsrAB sulfite reductase. DsrC contains two redox active cysteines in a flexible carboxy-terminal arm that are involved in the process of sulfite reduction or sulfur(1) compound oxidation in sulfur-reducing(2) or sulfur-oxidizing(3) organisms, respectively. In both processes, a disulfide formed between the two cysteines is believed to serve as the substrate of several proteins present in these organisms that are related to heterodisulfide reductases of methanogens. Here, we review the information on DsrC and its possible physiological partners, and discuss the idea that this protein may serve as a redox hub linking oxidation of several substrates to dissimilative sulfur metabolism. In addition, we analyze the distribution of proteins of the DsrC superfamily, including TusE that only requires the last Cys of the C-terminus for its role in the biosynthesis of 2-thiouridine, and a new protein that we name RspA (for regulatory sulfur-related protein) that is possibly involved in the regulation of gene expression and does not need the conserved Cys for its function. This article is part of a Special Issue entitled: 18th European Bioenergetic Conference. << Less

  Biochim Biophys Acta 1837:1148-1164(2014) [PubMed] [EuropePMC]

  This publication is cited by 5 other entries.

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

  Pott A.S., Dahl C.

  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 encode ... >> More

  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. << Less

  Microbiology 144:1881-1894(1998) [PubMed] [EuropePMC]

  This publication is cited by 5 other entries.

• Isolation of assimilatory- and dissimilatory-type sulfite reductases from Desulfovibrio vulgaris.

  Lee J.-P., LeGall J., Peck H.D. Jr.

  Bisulfite reductase (desulfoviridin) and an assimilatory sulfite reductase have been purified from extracts of Desulfovibrio vulgaris. The bisulfite reductase has absorption maxima at 628, 580, 408, 390, and 279 nm, and a molecular weight of 226,000 by sedimentation equilibrium, and was judged to ... >> More

  Bisulfite reductase (desulfoviridin) and an assimilatory sulfite reductase have been purified from extracts of Desulfovibrio vulgaris. The bisulfite reductase has absorption maxima at 628, 580, 408, 390, and 279 nm, and a molecular weight of 226,000 by sedimentation equilibrium, and was judged to be free of other proteins by disk electrophoresis and ultracentrifugation. On gels, purified bisulfite reductase exhibited two green bands which coincided with activity and protein. The enzyme appears to be a tetramer but was shown to have two different types of subunits having molecular weights of 42,000 and 50,000. The chromophore did not form an alkaline ferrohemochromogen, was not reduced with dithionite or borohydride, and did not form a spectrally visible complex with CO. The assimilatory sulfite reductase has absorption maxima at 590, 545, 405 and 275 nm and a molecular weight of 26,800, and appears to consist of a single polypeptide chain as it is not dissociated into subunits by sodium dodecyl sulfate. By disk electrophoresis, purified sulfite reductase exhibited a single greenish-brown band which coincided with activity and protein. The sole product of the reduction was sulfide, and the chromophore was reduced by borohydride in the presence of sulfite. Carbon monoxide reacted with the reduced chromophore but it did not form a typical pyridine ferrohemochromogen. Thiosulfate, trithionate, and tetrathionate were not reduced by either enzyme preparation. In the presence of 8 M urea, the spectrum of bisulfite reductase resembles that of the sulfite reductase, thus suggesting a chemical relationship between the two chromophores. << Less

  J. Bacteriol. 115:529-542(1973) [PubMed] [EuropePMC]

• Siroheme as an active catalyst in sulfite reduction.

  Seki Y., Sogawa N., Ishimoto M.

  Siroheme extracted by acetone/HCl treatment of sulfite reductase from yeast and purified by column chromatography catalyzed the reduction of sulfite to thiosulfate and sulfide when coupled with a hydrogen-hydrogenase-methyl viologen system. The activity increased with decrease in pH from 7 to 4, a ... >> More

  Siroheme extracted by acetone/HCl treatment of sulfite reductase from yeast and purified by column chromatography catalyzed the reduction of sulfite to thiosulfate and sulfide when coupled with a hydrogen-hydrogenase-methyl viologen system. The activity increased with decrease in pH from 7 to 4, and an apparent Km value of 50 mM for sulfite was obtained. In contrast to sirohydrochlorin plus Fe2+, addition of inorganic iron or 2,2'-bipyridine prior to the reduction reaction had scarcely any effect on the sulfite-reducing activity of siroheme. Hydroxylamine was reduced by siroheme at a much faster rate than sulfite, and the rate increased with increase in pH from 6 to 9. Siroheme extracted from Chromatium vinosum strain D sulfite reductase also reduced sulfite to thiosulfate and sulfide. << Less

  J Biochem 90:1487-1492(1981) [PubMed] [EuropePMC]

  This publication is cited by 5 other entries.

• Desulfoviridin, a multimeric-dissimilatory sulfite reductase from Desulfovibrio vulgaris (Hildenborough). Purification, characterization, kinetics and EPR studies.

  Wolfe B.M., Lui S.M., Cowan J.A.

  Conditions for the rigorous purification of desulfoviridin, the dissimilatory sulfite reductase from the sulfate-reducing bacterium Desulfovibrio vulgaris (Hildenborough) have been established. A final purification by fast protein liquid chromatography yields at least three distinct bands that eac ... >> More

  Conditions for the rigorous purification of desulfoviridin, the dissimilatory sulfite reductase from the sulfate-reducing bacterium Desulfovibrio vulgaris (Hildenborough) have been established. A final purification by fast protein liquid chromatography yields at least three distinct bands that each exhibit the characteristic absorption spectrum of desulfoviridin. Two of these have been extensively characterized by amino acid analysis, isoelectric focusing, polyacrylamide gel electrophoresis, and formulation of the prosthetic centers. Each contains two pairs of [Fe4S4] and siroheme units. These results stand in marked contrast to recent work claiming significant demetallation of siroheme, excess iron content, and the presence of Fe6S6 clusters. These proposals are critically assessed in light of our results and other published work. Steady-state kinetic parameters have been determined: kcat(SO3(2-) = 0.31 mol SO3(2-).s-1.mol heme-1, Km = 0.06 mM; kcat(NO2-) = 0.038 mol NO2-.s-1.mol heme-1, Km = 0.028 mM; kcat(NH2OH) = 29 mol NH2OH.s-1.mol heme-1, Km = 48 mM. A detailed comparison is made with the Escherichia coli and spinach assimilatory sulfite reductase enzymes and spinach nitrite reductase. Highly purified samples of dissimilatory sulfite reductase display an electron paramagnetic resonance spectrum characteristic of rhombic high spin ferric heme centers, while the fully reduced enzyme shows EPR features typical of [Fe4S4] clusters. The magnetic properties of the prosthetic centers are further characterized by variable temperature experiments and spin quantitation. << Less

  Eur. J. Biochem. 223:79-89(1994) [PubMed] [EuropePMC]