A seven-iron ferredoxin from the thermoacidophilic archaeon Desulfurolobus ambivalens.
A seven-iron ferredoxin was isolated from aerobically grown cells of the hyperthermoacidophilic archaeon Desulfurolobus ambivalens (DSM 3772). The protein is monomeric, with an apparent molecular mass of 15 kDa and contains 7 iron atoms/molecule. The N-terminal sequence shows a large similarity (70% identity) with that of the ferredoxin isolated from the archaeon Sulfolobus acidocaldarius. The EPR characteristics in both the native (oxidized) and dithionite-reduced states of this protein allowed an unequivocal identification of a [3Fe-4S]1+/0 center, with a reduction potential of -270 +/- 20 mV, at pH 7.5. The protein also contains a [4Fe-4S]2+/1+ center with a very low reduction potential (Eo = -540 mV, pH 7.0), which yields a rhombic EPR spectrum upon reduction with sodium dithionite at high pH. The reduction potentials of both centers are slightly pH dependent between pH 6 and 9. The [3Fe-4S] ferredoxin center is able to accept electrons from pyruvate oxidase and NADH oxidase isolated from D. ambivalens. This ferredoxin is present in large amounts (at least 130 mg/kg wet cells), which allowed the unequivocal observation of oxidized [3Fe-4S] clusters in intact D. ambivalens cells.
Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal.
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M
Teixeira
R
R
Batista
A P
AP
Campos
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C
Gomes
J
J
Mendes
I
I
Pacheco
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Anemuller
W R
WR
Hagen
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001105:Archaea / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D005288:Ferredoxins / Q000737:chemistry* / Q000302:isolation & purification / Q000502:physiology; D007501:Iron / Q000032:analysis*; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D013056:Spectrophotometry, Ultraviolet
D000596:Amino Acids; D005288:Ferredoxins; D007501:Iron