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Dg ferredoxin gene was cloned using the polymerase chain reaction (PCR), inserted into vector pT7-7, and overexpressed in Escherichia coli (E. coli) grown in aerobic media. The recombinant protein is a dimer and contains a [3Fe-4S] cluster per monomer. EPR and (1)H NMR data of recombinant and wild-type protein are compared.

A monoheme cytochrome c553 and a hexadecaheme high molecular weight cytochrome (Hmc) have been isolated and characterized from the sulfate-reducing bacteria Desulfovibrio desulfuricans G201, in addition to the tetraheme cytochrome c3 (Mr 13000) that has been previously described. Both cytochromes are homologous with respect to several biochemical properties to the corresponding cytochromes found in other Desulfovibrio species. However, they are acidic proteins while the corresponding molecules, isolated from other Desulfovibrio species, are relatively more basic. The D. desulfuricans cytochrome content appears identical to that of D. vulgaris Hildenborough. Isolation of these cytochromes from a Desulfovibrio desulfuricans strain is of great interest in order to get more insight on the physiological function of these molecules.

The regulation of the properties of Desulfovibrio gigas flavodoxin in AOT/water/iso-octane micellar system was studied. UV-visible spectroscopic studies have shown that photoreduction of flavodoxin in the presence of EDTA leads to hydroquinone formation through the intermediate semiquinone. The [free FMN] - [bound to flavodoxin FMN] equilibrium (and hence, the amount of apoprotein) depends on redox state of FMN and on hydration degree which controls the micellar size. Thus, a new method of reversible cofactor removing under mild conditions (at low hydration degree of micelles) is suggested, accompained by isolation of apo-form of the protein.

Rubredoxin and desulforedoxin both contain an Fe(S-Cys)4 center. However, the spectroscopic properties of the center in desulforedoxin differ from rubredoxin. These differences arise from a distortion of the metal site hypothesized to result from adjacent cysteine residues in the primary sequence of desulforedoxin. Two desulforedoxin mutants were generated in which either a G or P-V were inserted between adjacent cysteines. Both mutants exhibited optical spectra with maxima at 278, 345, 380, 480, and 560 nm while the low temperature X-band EPR spectra indicated highspin Fe3+ ions with large rhombic distortions (E/D = 0.21-0.23). These spectroscopic properties are distinct from wild type desulforedoxin and virtually identical to rubredoxin.

Desulforedoxin is a protein purified from cellular extracts of Desulfovibrio gigas. It is a small (7.9 kDa) dimeric protein that contains a distorted rubredoxin like center (one single iron coordinated by four cysteinyl residues). Due to the simplicity of the polypeptide chain and of the iron center, an attempt was made to chemically produce this protein. A 36 amino acid polypeptide chain was synthesized based on the known sequence of native Desulforedoxin. The iron center was then reconstituted and the biochemical and spectroscopic characteristics of this synthetic protein were investigated. The final product has an equal sequence to the protein purified from D. gigas. The synthetic and natural Dx are very similar, in terms redox potential and spectroscopic properties (UV-Visible, EPR, Mössbauer).