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1981
Johnson, MK, Hare JW, Spiro TG, Moura JJ, Xavier AV, Legall J.  1981.  Resonance Raman spectra of three-iron centers in ferredoxins from Desulfovibrio gigas, Oct 10. J Biol Chem. 256:9806-8., Number 19 AbstractWebsite

The resonance Raman spectra of ferredoxins (Fd) I and II from Desulfovibrio gigas are reported using 4579 A Ar+ laser excitation. The (3Fe-3S) center in Fd II has a characteristic resonance Raman spectrum, readily distinguishable from those of (2Fe-2S) or (4Fe-4S) clusters. Reduction of Fd II produces a marked alteration in the resonance Raman spectrum. Fd I is shown to contain both (3Fe-3S) and (4Fe-4S) Fd-type clusters. The results illustrate the potential of resonance Raman spectroscopy in Fe-S cluster identification, even in cases where more than one cluster type is present.

1980
Huynh, BH, Moura JJ, Moura I, Kent TA, Legall J, Xavier AV, Munck E.  1980.  Evidence for a three-iron center in a ferredoxin from Desulfovibrio gigas. Mossbauer and EPR studies, Apr 25. J Biol Chem. 255:3242-4., Number 8 AbstractWebsite

The tetrameric form of a Desulfovibrio gigas ferredoxin, named Fd II, mediates electron transfer between cytochrome c3 and sulfite reductase. We have studied two stable oxidation states of this protein with Mossbauer spectroscopy and electron paramagnetic resonance. We found 3 iron atoms/monomer and a spin concentration of 0.9 spins/monomer for the oxidized protein. Taken together, the EPR and Mossbauer data demonstrate conclusively the presence of a spin-coupled structure containing 3 iron atoms and labile sulfur. The Mossbauer data show also that this metal center is structurally similar, if not identical, with the low potential center of a ferredoxin from Azotobacter vinelandii, a novel cluster described recently (Emptage, M.H., Kent, T.A., Huynh, B.H., Rawlings, J., Orme-Johnson, W.H., and Munck, E. (1980) J. Biol. Chem. 255, 1793-1796).

Moura, I, Huynh BH, Hausinger RP, Legall J, Xavier AV, Munck E.  1980.  Mossbauer And Electron-Paramagnetic-Res Studies Of Desulforedoxin From Desulfovibrio-Gigas, 1980. Journal of Biological Chemistry. 255:2493-2498., Number 6 AbstractWebsite
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Moura, I, Huynh B, Legall J, Xavier AV, Munck E.  1980.  EPR and Mossbauer studies of desulforedoxin from Desulfovibrio gigas. Ciênc. Biol. (Portugal). 5:199-201. Abstract
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1978
Moura, JJ, Xavier AV, Hatchikian EC, Legall J.  1978.  Structural control of the redox potentials and of the physiological activity by oligomerization of ferredoxin, May 1. FEBS Lett. 89:177-9., Number 1 AbstractWebsite
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Moura, JJ, Xavier AV, Cammack R, Hall DO, Bruschi M, Legall J.  1978.  Oxidation-reduction studies of the Mo-(2Fe-2S) protein from Desulfovibrio gigas, Aug 1. Biochem J. 173:419-25., Number 2 AbstractWebsite

Potentiometric titration followed by e.p.r. measurements were used to determine the midpoint reduction potentials of the redox centres of a molybdenum-containing iron-sulphur protein previously isolated from Desulfovibrio gigas, a sulphate-reducing bacterium (Moura, Xavier, Bruschi, Le Gall, Hall & Cammack (1976) Biochem. Biophys. Res. Commun. 728 782-789; Moura, Xavier, Bruschi, Le Gall & Cabral (1977) J. Less Common Metals 54, 555-562). The iron-sulphur centres could readily be distinguished into three types by means of g values, temperature effect, oxidation-reduction potential values and reduction rates. The type-I Fe-S centres are observed at 77 K. They show mid-point potential values of -260mV (Fe-S type IA) and -440 mV (Fe-S type IB). Centres of types IA and IB appear to have similar spectra at 77 K and 24 K. The Fe-S type-II centres are only observed below 65 K and have a midpoint potential of -28mV. Long equilibration times (30 min) with dye mediators under reducing conditions were necessary to observe the very slow equilibrating molybdenum signals. The potential values associated with this signal were estimated to be approx. -415 mV for Mo(VI)/Mo(V) and-530mV for Mo(V)/Mo(IV).

1977
Cammack, R, Rao KK, Hall DO, Moura JJ, Xavier AV, Bruschi M, Legall J, Deville A, Gayda JP.  1977.  Spectroscopic studies of the oxidation-reduction properties of three forms of ferredoxin from Desulphovibrio gigas, Feb 22. Biochim Biophys Acta. 490:311-21., Number 2 AbstractWebsite

Electron paramagnetic resonance spectra were recorded of three forms of Desulphovibrio gigas ferredoxin, FdI, FdI' and FdII. The g = 1.94 signal seen in dithionite-reduced samples is strong in FdI, weaker in FdI' and very small in FdII. The g = 2.02 signal in the oxidized proteins is weak in FdI and strongest in FdII. It is concluded that most of the 4Fe-4S centres in FdI change between states C- and C2-; FdI' contain both types of centre. There is no evidence that any particular centre can change reversibly between all three oxidation states. Circular dichroism spectra show differences between FdI and FdII even in the diamagnetic C2- state. The redox potentials of the iron-sulphur centres of the three oligomers (forms) are different. After formation of the apo-protein of FdII and reconstitution with iron and sulphide, the protein behaves more like FdI, showing a strong g = 1.94 signal in the reduced states.

1976
Moura, JJ, Xavier AV, Bruschi M, Legall J, Hall DO, Cammack R.  1976.  A molybdenum-containing iron-sulphur protein from Desulphovibrio gigas, Oct 4. Biochem Biophys Res Commun. 72:782-9., Number 3 AbstractWebsite
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Bruschi, M, Hatchikian C, Legall J, Moura JJ, Xavier AV.  1976.  Purification, characterization and biological activity of three forms of ferredoxin from the sulfate-reducing bacterium Desulfovibrio gigas, Nov 9. Biochim Biophys Acta. 449:275-84., Number 2 AbstractWebsite

Three forms of ferredoxin FdI, FdI', and FdII have been isolated from Desulfovibrio gigas, a sulfate reducer. They are separated by a combination of DEAE-cellulose and gel filtration chromatographic procedures. FdI and FdI' present a slight difference in isoelectric point which enables the separation of the two forms over DEAE-cellulose, while FdII is easily separated from the two other forms by gel filtration. The three forms have the same amino acid composition and are isolated in different aggregation states. Molecular weight determinations by gel filtration gave values of 18 000 for FdI and FdI' and 24 000 for FdII, whereas a value of 6000 is determined when dissociation is accomplished with sodium dodecyl sulfate. The electronic spectra are different and their ultraviolet-visible absorbance rations are 0.77, 0.87 and 0.68 respectively for FdI, FdI' and FdII. Despite these differences, the physiological activities of the three forms are similar as far as the reduction of sulfite by molecular hydrogen is concerned.

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