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Last modified: 20 November 1998

Desulfoferrodoxin
Iron centre Formal iron oxidation states
I
Fe(Cys)4 image
Fe(SgammaCys)4
FeII; FeIII
II
Fe(Cys)(His)4 image
FeSgammaCysNdeltaHis(NepsilonHis)3
FeII; FeIII

Desulfoferrodoxin (Dfx) is a fusion protein [1] containing a small N­terminal desulforedoxin­type domain (domain I) [2] and a larger C­terminal domain similar to neelaredoxin (domain II) [3]. Dfx was isolated from Desulfovibrio desulfuricans in two oxidation states: the oxidised (grey) form and the semi­reduced (pink) form. Dfx contains two different iron centres called centre I (desulforedoxin­type) and centre II. The large difference between the midpoint redox potentials for Dfx iron centres (4 mV for centre I, 240 mV for centre II) allows the separation of the protein into three oxidation states:

The 3­D structure of Dfx from Desulfovibrio desulfuricans has been solved [4]. Dfx exists as a two­fold symmetric dimer. The monomer consists of two domains each containing an iron centre, with both iron atoms close to the molecular surface. Domain I (34 residues) has an approximately spherical shape similar to the structure of desulforedoxin and is composed of a three­stranded antiparallel ß­structure which is extended upon dimer formation, resulting in a small incomplete ß­barrel. The iron centre I has a distorted tetrahedral coordination and is bound to four cysteinyl residues (Cys­9, Cys­12, Cys­28 and Cys­29). Domain II (88 residues) consists of a 3+4 ß­sheet structure, typical of the fibronectin III fold. Four ß­strands (ß3 a-d) from each monomer form the eight­stranded antiparallel ß­sheet that extends through the molecule. The iron coordination in centre II can be described as square pyramidal, with the four nitrogen ligands at the equatorial positions (Nepsilon of His­48, His­68, His­74 and Ndelta of His­118) and the sulphur of Cys­115 at the axial position. The sixth iron position is accessible to solvent. A Ca2+ ion has also been found at the dimer interface coordinated to the eight oxygen ligands and was suggested to contribute to dimer stabilisation [4].

Desulfoferrodoxins in SWISS­PROT/TREMBL

O29425 DESR_ARCFU Desulfoferrodoxin homolog (Dfx); Archaeoglobus fulgidus
Q46495 DESR_DESBR Desulfoferrodoxin (Rbo); Desulfoarculus baarsii
P22076 DESR_DESDE Desulfoferrodoxin (Dfx); Desulfovibrio desulfuricans
P20418 DESR_DESVH Desulfoferrodoxin (Dfx); Desulfovibrio vulgaris (strain Hildenborough)
P48345 DESR_DESVM Desulfoferrodoxin (Dfx); Desulfovibrio vulgaris (strain Miyazaki)
O26851 DESR_METTH Desulfoferrodoxin homolog (Dfx); Methanobacterium thermoautotrophicum
G3323136 G3323136 Desulfoferrodoxin (Rbo); Treponema pallidum
O50258 NLR_DESGI Neelaredoxin; Desulfovibrio gigas
O29903 NLRH_ARCFU Neelaredoxin homolog; Archaeoglobus fulgidus
Q58151 NLRH_METJA Neelaredoxin homolog; Methanococcus jannaschii
O58810 NLRH_PYRHO Neelaredoxin homolog; Pyrococcus horikoshii

Desulfoferrodoxins in alignment databases

Protein Superfamily Protein Homology Domain Pfam LPFC 3­D alignment
00212; desulfoferrodoxin 00116; desulforedoxin
-
-

Desulfoferrodoxin in 3­D databases

Desulfoferrodoxin contains two mononuclear iron centres.

PDB scop BSMRELI
Base		 HeaderMMS Abstract ¹
1dfx
-
 1dfx 1dfx Putidaredoxin (oxidised); Pseudomonas putida, strain ATCC 17453)
-

¹ Macromolecular Structures abstract. Full text is available to BioMedNet Members

References

  1. Brumlik, M.J., Leroy, G., Bruschi, M. and Voordouw, G. (1990) The nucleotide sequence of the Desulfovibrio gigas desulforedoxin gene indicates that the Desulfovibrio vulgaris rbo gene originated from a gene fusion event. J. Bacteriol. 172, 7289-7292.
  2. Moura, I., Tavares, P., Moura, J.J.G., Ravi, N., Huynh, B.­H., Liu, M.Y. and LeGall, J. (1990) Purification and characterization of desulfoferrodoxin. A novel protein from Desulfovibrio desulfuricans (ATCC 27774) and from Desulfovibrio vulgaris (strain Hildenborough) that contains a distorted rubredoxin center and a mononuclear ferrous center. J. Biol. Chem. 265, 21596-21602.
  3. Chen, L., Sharma, P., Le Gall, J., Mariano, A.M., Teixeira, M. and Xavier, A.V. (1994) A blue non­heme iron protein from Desulfovibrio gigas. Eur. J. Biochem. 226, 613-618.
  4. Coelho, A.V., Matias, P.M., Fülöp, V., Thompson, A., Gonzalez, A. and Carrondo, M.A. (1997) Desulfoferrodoxin structure determined by MAD phasing and refinement to 1.9­Å resolution reveals a unique combination of a tetrahedral FeS4 centre with a square pyramidal FeSN4 centre. J. Biol. Inorg. Chem. 2, 680-689.
Bibliography on structural studies of desulfoferrodoxin