Characterization of two dissimilatory sulfite reductases (desulforubidin and desulfoviridin) from the sulfate-reducing bacteria.  Moessbauer and EPR studies

Moura, Isabel; LeGall, Jean; Lino, A.R.; Peck, Harry D.; Fauque, Guy; Xavier, António V.; Dervartanian, D.V.; Moura, José J. G.; Huynh, Boi Hanh

doi:10.1021/ja00212a013

Cited by 67 publications

(43 citation statements)

References 6 publications

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“…One datum appears to be at variance with this conclusion, namely, the observation of a ferredoxin-like 'g = 1.93' spectrum in the reduced enzyme. We have only observed trace amounts of this spectrum in terms of S = 1/2 spin concentration/enzyme concentration (the model of Moura et al [31] would predict four spins/enzyme molecule). However, others have succeeded in boosting this intensity in the E. coli enzyme to near stoichiometry in samples in which the siroheme was previously complexed with CO or with C N - [12].…”

Section: Discussionmentioning

confidence: 75%

“…Extrapolation of these data, would fix the number of non-heme iron atoms to between four and nine/siroheme molecule. In a later determination, only 5.1 Fe and 3.4 S2-atoms were found/p monomer in protein which contained a stoichiometric amount of siroheme [12] [31]. The authors have proposed an interpretation very different from ours.…”

Section: Discussionmentioning

confidence: 76%

“…1 in the form of wide-scan spectra of concentrated samples from three different isolations. There is considerable EPR-spectral variation over the different samples; this has been noted before to be the case for dissimilatory sulfite reductases from other sulfate-reducing bacteria [4,31,411 and recently also for an activated form of assimilatory sulfite reductase [42]. Several high-spin heme components are observed with g, and g, values centered around g % 6 in the range 7-5, and with a g, value in the range 2.0 -1.9.…”

Section: Epr Spectra Of Oxidized Desulfoviridinmentioning

confidence: 94%

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S= 9/2 EPR signals are evidence against coupling between the siroheme and the Fe/S cluster prosthetic groups in Desulfovibrio vulgaris (Hildenborough) dissimilatory sulfite reductase

Pierik

Hagen

1991

European Journal of Biochemistry

111

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Eur. J. Biochem. 195, 505-516 (1991) Sulfite reductases contain siroheme and iron-sulfur cluster prosthetic groups. The two groups are believed to be structurally linked via a single, common ligand. This chemical model is based on a magnetic model for the oxidized enzyme in which all participating iron ions are exchange coupled. This description leads to two serious discrepancies. Although the iron-sulfur cluster is assumed to be a diamagnetic cubane, [4Fe-4SI2 +, all iron appears to be paramagnetic in Mossbauer spectroscopy. On the other hand, EPR spectroscopy has failed to detect anything but a single high-spin heme. We have re-addressed this problem by searching for new EPR spectroscopic clues in concentrated samples of dissimilatory sulfite reductase from Desulfovibrio vulgaris (Hildenborough). We have found several novel signals with effective g values of 17, 15.1, 11.7,9.4, 9.0, 4. The signals are interpreted in terms of an S = 9/2 system with spin-Hamiltonian parameters g = 2.00, D = -0.56 cm-', I E/D I = 0.1 3 for the major component. In a reductive titration with sodium borohydride the spectrum disappears with Em = -205 mV at pH 7.5. Contrarily, the major high-spin siroheme component has S = 512, g = 1.99, D = + 9 cm-', I EID I = 0.042, and Em = -295 mV. The sum of all siroheme signals integrates to 0.2 spin/half molecule, indicating considerable demetallation of this prosthetic group. Rigorous quantification procedures for S = 9/2 are not available, however, estimation by an approximate method indicates 0.6 S = 9/2 spin/half molecule. The S = 9/2 system is ascribed to an iron-sulfur cluster. It follows that this cluster is probably not a cubane, is not necessarily exchange-coupled to the siroheme, and, therefore, is not necessarily structurally close to the siroheme. It is suggested that this ironsulfur prosthetic group has a novel structure suitable for functioning in multiple electron transfer.Metalloenzymes which catalyze redox reactions are frequently complex bioinorganic systems. They contain more than one prosthetic group in order to be able to function in two distinguishable operations. They should be an appropriate sink for a (usually even) number of reducing equivalents. They should also bind and activate substrate(s) for the subsequent combination with stored electrons.Nature uses the grouping of metal ions into clusters and the grouping of clusters into multi-center systems to increase the versatility of metalloproteins as redox compounds. Specifically, this grouping is to extend drastically the range of available reduction midpoint potentials associated with a particular metal, in order to create the possibility to transfer pairs, or multiple pairs, of electrons, and in order to optimize the energetics of electron transfer. Thus, the topological grouping of metal ions (or, more generally, of entities which carry potentially reactive electrons) results in biologically useful electronic cooperativity.These electronic interactions are, by necessity, accompanied by their associated magnetic...

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Section: Discussionmentioning

confidence: 75%

Section: Discussionmentioning

confidence: 76%

Section: Epr Spectra Of Oxidized Desulfoviridinmentioning

confidence: 94%

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S= 9/2 EPR signals are evidence against coupling between the siroheme and the Fe/S cluster prosthetic groups in Desulfovibrio vulgaris (Hildenborough) dissimilatory sulfite reductase

Pierik

Hagen

1991

European Journal of Biochemistry

111

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“…ln the case of desulfoviridin the sirohaems are about 80% demetallated 17-91; the reason for this is not yet known. The enzyme also contains a high amount of iron and acid-labile sulfide: desulfoviridin from D. vulgaris and D. gigas has been reported to contain about 22 and 18 iron atoms/ molecule, respectively [8,91.…”

mentioning

confidence: 99%

“…Initial reports have emphasized spectroscopic similarities between assimilatory and dissimilatory sulfite reductases [8,10,111, suggesting a similarity in active-site structure (i.e. a cubanecoupled sirohaem).…”

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confidence: 99%

Dissimilatory Sulfite Reductase Revisited

Marritt

Hagen

1996

European Journal of Biochemistry

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Assimilatory sulfite reductase contains a sirohaem that is very weakly coupled to a [4Fe-4S] cubane, i.e. five iron atoms in total. Dissimilatory sulfite reductase is a complex system with 20 Fe atoms/a,p,y, hexamer. A recent revision of the purification procedure for the Desulfovibrio vulgaris dissimilatory enzyme has afforded a preparation of only 10 Fe atoms hexamer, this has led to the conclusion that the topology of prosthetic groups parallels that of the assimilatory system [Wolfe, €3. M., Lui, S. M. & Cowan, J. A. (1994) Eur: J. Biochem. 223, 79-89]. The new purification procedure has been reproduced but the claimed molecular properties are not reproducible. The highly purified, active desulfoviridin contains 20, not 10, Fe atoms/molecule ; the sirohaem is extensively demetallated, not metallated; and the S = 9/2 iron-sulfur cluster is present, not absent.Keywords: dissimilatory sulfite reductase; desulfoviridin.S(IV) is biologically activated and reduced to S(I1) by the iron-sulfur sirohaemoenzyme sulfite reductase. Assimilatory sulfite reductase catalyses the concerted six-electron reduction of sulfite to sulfide for the biosynthesis of organic sulfur compounds. The crystallographic structure of the E.scherichia coli ylfite reductase haemoprotein has recently been solved to 1.6-A resolution [I]. The sirohaem is bridged to a [4Fe-4S] cubane via a cysteine thiolate ligand.Sulfite can also act as the final electron acceptor in the respiration of anaerobic microorganisms. This dissimilatory sulfite reductase activity is performed by a more complex enzyme system; in DesuZjbvibrio vulgaris (Hildenborough) this sulfite reductase is of the desulfoviridin type, classified according to its characteristic visible absorption spectrum [2-41. It is isolated as an a2p2y2 hcxamcr with subunit molecular masses of 50 kDa (a), 40 kDa @) and 11 kDa (1' ) [5]. The protein contains two sirohaems, one for each a subunit, believed to be the sites of substrate reduction [6]. ln the case of desulfoviridin the sirohaems are about 80% demetallated 17-91; the reason for this is not yet known. The enzyme also contains a high amount of iron and acid-labile sulfide: desulfoviridin from D. vulgaris and D. gigas has been reported to contain about 22 and 18 iron atoms/ molecule, respectively [8, 91.The arrangement of this iron-sulfur has not becn established. Initial reports have emphasized spectroscopic similarities between assimilatory and dissimilatory sulfite reductases [8, 10, 111, suggesting a similarity in active-site structure (i.e. a cubanecoupled sirohaem). We have questioned this proposal when we discovered S = 9/2 EPR signals from what appears to be a noninteracting iron-sulfur structure in desulfoviridin from D. vulgaris [9]. Subsequent studies showed that the S = 912 EPR is These authors claim that the resulting preparations contain only 10 Fe atoms a,~,y2 hexamer, and they suggest that this results from purifying away an unidentified contaminating iron protein.It is also claimed that the sirohaem in the new preparations ...

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Biocorrosion: Role of Sulfate Reducing Bacteria

Beech

2003

Encyclopedia of Environmental Microbiology

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Characterization of two dissimilatory sulfite reductases (desulforubidin and desulfoviridin) from the sulfate-reducing bacteria. Moessbauer and EPR studies

Cited by 67 publications

References 6 publications

S= 9/2 EPR signals are evidence against coupling between the siroheme and the Fe/S cluster prosthetic groups in Desulfovibrio vulgaris (Hildenborough) dissimilatory sulfite reductase

S= 9/2 EPR signals are evidence against coupling between the siroheme and the Fe/S cluster prosthetic groups in Desulfovibrio vulgaris (Hildenborough) dissimilatory sulfite reductase

Dissimilatory Sulfite Reductase Revisited

Biocorrosion: Role of Sulfate Reducing Bacteria

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