Structural control of the redox potentials and of the physiological activity by oligomerization of ferredoxin,
Moura, J. J., Xavier A. V., Hatchikian E. C., and Legall J.
, FEBS Lett, May 1, Volume 89, Number 1, p.177-9, (1978)
Abstractn/a
Oxidation-reduction studies of the Mo-(2Fe-2S) protein from Desulfovibrio gigas,
Moura, J. J., Xavier A. V., Cammack R., Hall D. O., Bruschi M., and Legall J.
, Biochem J, Aug 1, Volume 173, Number 2, p.419-25, (1978)
AbstractPotentiometric 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).
A comparative spectroscopic study of two non-haem iron proteins lacking labile sulphide from Desulphovibrio gigas,
Moura, I., Xavier A. V., Cammack R., Bruschi M., and Legall J.
, Biochimica et Biophysica Acta (BBA) - Protein Structure, Volume 533, Number 1, p.156-162, (1978)
Abstractn/a
NMR studies of electron carrier proteins from sulphate reducing bacteria,
Xavier, A. V., and Moura J. J.
, Biochimie, Volume 60, Number 3, p.327-38, (1978)
AbstractThe sulphate-reducing bacteria have a complex electron transfer system which leads to the reduction of sulphate by oxidation of either organic substrates or molecular hydrogen. These bacteria can either produce or consume molecular hydrogen. The central part of this electron pathway for Desulovibrio gigas is constituted by hydrogenase (3 X (4Fe-4S)). cytochrome c3 (4 haems with different redox potentials) and a one (4Fe-4S) cluster ferredoxin. This ferredoxin is isolated in different oligomeric forms, which stabilize different oxidation states and have different physiological roles; the trimer FdI being involved in the production of H2 and the tetramer FdII being more efficient for the consumption of H2. The presence of intrinsic probes (the iron ions) in these proteins is particularly helpful for structural studies using NMR spectroscopy. These studies allowed a characterization of the oxidation states used by the different oligomers of the ferredoxin and obtaintion of structural information on multi-haem cytochromes (c3 and c7). NMR is also suitable to study protein-protein interaction. The study of the complex formed between FdII and cytochrome c3 has shown that there is an alteration of the kinetics of electron transfer upon complexation.