title: Primary sequence, oxidation-reduction potentials and tertiary-structure prediction of Desulfovibrio desulfuricans ATCC 27774 flavodoxin.
abstract: Flavodoxin was isolated and purified from Desulfovibrio desulfuricans ATCC 27774, a sulfate-reducing organism that can also utilize nitrate as an alternative electron acceptor. Mid-point oxidation-reduction potentials of this flavodoxin were determined by ultraviolet/visible and EPR methods coupled to potentiometric measurements and their pH dependence studied in detail. The redox potential E2, for the couple oxidized/semiquinone forms at pH 6.7 and 25 degrees C is -40 mV, while the value for the semiquinone/hydroquinone forms (E1), at the same pH, -387 mV. E2 varies linearly with pH, while E1 is independent of pH at high values. However, at low pH (< 7.0), this value is less negative, compatible with a redox-linked protonation of the flavodoxin hydroquinone. A comparative study is presented for Desulfovibrio salexigens NCIB 8403 flavodoxin [Moura, I., Moura, J.J.G., Bruschi, M. & LeGall, J. (1980) Biochim. Biophys. Acta 591, 1-8]. The complete primary amino acid sequence was obtained by automated Edman degradation from peptides obtained by chemical and enzymic procedures. The amino acid sequence was confirmed by FAB/MS. Using the previously determined tridimensional structure of Desulfovibrio vulgaris flavodoxin as a model [similarity, 48.6%; Watenpaugh, K.D., Sieker, L.C., Jensen, L.H., LeGall, J. & Dubourdieu M. (1972) Proc. Natl Acad. Sci. USA 69, 3185-3188], the tridimensional structure of D. desulfuricans ATCC 27774 flavodoxin was predicted using AMBER force-field calculations.
authors.affiliation: Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Monte de Caparica, Portugal.
authors.forename: J
authors.initials: J
authors.lastname: Caldeira
authors.forename: P N
authors.initials: PN
authors.lastname: Palma
authors.forename: M
authors.initials: M
authors.lastname: Regalla
authors.forename: J
authors.initials: J
authors.lastname: Lampreia
authors.forename: J
authors.initials: J
authors.lastname: Calvete
authors.forename: W
authors.initials: W
authors.lastname: Schäfer
authors.forename: J
authors.initials: J
authors.lastname: Legall
authors.forename: I
authors.initials: I
authors.lastname: Moura
authors.forename: J J
authors.initials: JJ
authors.lastname: Moura
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003901:Desulfovibrio / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D005418:Flavodoxin / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013056:Spectrophotometry, Ultraviolet; D013057:Spectrum Analysis
chemical_list: D005418:Flavodoxin