title: On the two iron centers of desulfoferrodoxin.
abstract: Desulfoferrodoxin from Desulfovibrio vulgaris, strain Hildenborough, is a homodimer of 28 kDa; it contains two Fe atoms per 14.0 kDa subunit. The N-terminal amino-acid sequence is homogeneous and corresponds to the previously described Rho gene, which encodes a highly charged 14 kDa polypeptide without a leader sequence. Although one of the two iron centers, FeA, has previously been described as a 'strained rubredoxin-like' site, EPR of the ferric form proves very similar to that of the pentagonal bipyramidally coordinated iron in ferric complexes of DTPA, diethylenetriaminepentaacetic acid: both systems have spin S = 5/2 and rhombicity E/D = 0.08. Unlike the Fe site in rubredoxin the FeA site in desulfoferrodoxin has a pH dependent midpoint potential with pKox = 9.2 and pKred = 5.3. Upon reduction (Em,7.5 = +2 mV) FeA exhibits an unusually sharp S = 2 resonance in parallel-mode EPR. The second iron, FeB, has S = 5/2 and E/D = 0.33; upon reduction (Em,7.5 = +90 mV) FeB turns EPR-silent.
authors.affiliation: Department of Biochemistry, Agricultural University, Wageningen, The Netherlands.
authors.forename: M F
authors.initials: MF
authors.lastname: Verhagen
authors.forename: W G
authors.initials: WG
authors.lastname: Voorhorst
authors.forename: J A
authors.initials: JA
authors.lastname: Kolkman
authors.forename: R B
authors.initials: RB
authors.lastname: Wolbert
authors.forename: W R
authors.initials: WR
authors.lastname: Hagen
mesh_terms: D000595:Amino Acid Sequence; D000906:Antibodies; D016969:Desulfovibrio vulgaris / Q000737:chemistry; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D005288:Ferredoxins / Q000737:chemistry* / Q000276:immunology; D007501:Iron / Q000737:chemistry*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction
chemical_list: D000906:Antibodies; D005288:Ferredoxins; C066602:desulfoferrodoxin; D007501:Iron