title: The superoxide dismutase activity of desulfoferrodoxin from Desulfovibrio desulfuricans ATCC 27774.
abstract: Desulfoferrodoxin (Dfx), a small iron protein containing two mononuclear iron centres (designated centre I and II), was shown to complement superoxide dismutase (SOD) deficient mutants of Escherichia coli [Pianzzola, M.J., Soubes M. & Touati, D. (1996) J. Bacteriol. 178, 6736-6742]. Furthermore, neelaredoxin, a protein from Desulfovibrio gigas containing an iron site similar to centre II of Dfx, was recently shown to have a significant SOD activity [Silva, G., Oliveira, S., Gomes, C.M., Pacheco, I., Liu, M.Y., Xavier, A.V., Teixeira, M., Le Gall, J. & Rodrigues-Pousada, C. (1999) Eur. J. Biochem. 259, 235-243]. Thus, the SOD activity of Dfx isolated from the sulphate-reducing bacterium Desulfovibrio desulfuricans ATCC 27774 was studied. The protein exhibits a SOD activity of 70 U x mg-1, which increases approximately 2.5-fold upon incubation with cyanide. Cyanide binds specifically to Dfx centre II, yielding a low-spin iron species with g-values at 2.27 (g perpendicular) and 1.96 (g parallel). Upon reaction of fully oxidized Dfx with the superoxide generating system xanthine/xanthine oxidase, Dfx centres I and II become partially reduced, suggesting that Dfx operates by a redox cycling mechanism, similar to those proposed for other SODs. Evidence for another SOD in D. desulfuricans is also presented - this enzyme is inhibited by cyanide, and N-terminal sequence data strongly indicates that it is an analogue to Cu,Zn-SODs isolated from other sources. This is the first indication that a Cu-containing protein may be present in a sulphate-reducing bacterium.
authors.affiliation: Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Partugal.
authors.forename: C V
authors.initials: CV
authors.lastname: Romão
authors.forename: M Y
authors.initials: MY
authors.lastname: Liu
authors.forename: J
authors.initials: J
authors.lastname: Le Gall
authors.forename: C M
authors.initials: CM
authors.lastname: Gomes
authors.forename: V
authors.initials: V
authors.lastname: Braga
authors.forename: I
authors.initials: I
authors.lastname: Pacheco
authors.forename: A V
authors.initials: AV
authors.lastname: Xavier
authors.forename: M
authors.initials: M
authors.lastname: Teixeira
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D003486:Cyanides / Q000378:metabolism; D003901:Desulfovibrio / Q000201:enzymology* / Q000235:genetics; D005288:Ferredoxins / Q000378:metabolism*; D007700:Kinetics; D008667:Metalloproteins / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D016415:Sequence Alignment; D013482:Superoxide Dismutase / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism; D019820:Xanthine; D014969:Xanthine Oxidase / Q000378:metabolism
chemical_list: D003486:Cyanides; D005288:Ferredoxins; D008667:Metalloproteins; C066602:desulfoferrodoxin; D013481:Superoxides; D019820:Xanthine; D013482:Superoxide Dismutase; D014969:Xanthine Oxidase