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2004
Structural basis for the mechanism of Ca2+ activation of the di-heme cytochrome c peroxidase from Pseudomonas nautica 617, Dias, J. M., Alves T., Bonifacio C., Pereira A. S., Trincao J., Bourgeois D., Moura I., and Romão M. J. , Structure, Jul, Volume {12}, Number {6}, 1100 MASSACHUSETTS AVE, CAMBRIDGE, MA 02138 USA, p.{961-973}, (2004) Abstract

Cytochrome c peroxidase (CCP) catalyses the reduction of H2O2 to H2O, an important step in the cellular detoxification process. The crystal structure of the di-heme CCP from Pseudomonas nautica 617 was obtained in two different conformations in a redox state with the electron transfer heme reduced. Form IN, obtained at pH 4.0, does not contain Ca2+ and was refined at 2.2 Angstrom resolution. This inactive form presents a closed conformation where the peroxidatic heme adopts a six-ligand coordination, hindering the peroxidatic reaction from taking place. Form OUT is Ca2+ dependent and was crystallized at pH 5.3 and refined at 2.4 Angstrom resolution. This active form shows an open conformation, with release of the distal histidine (His71) ligand, providing peroxide access to the active site. This is the first time that the active and inactive states are reported for a di-heme peroxidase.

2003
Formation of a stable cyano-bridged dinuclear iron cluster following oxidation of the superoxide reductases from Treponema pallidum and Desulfovibrio vulgaris with K3Fe(CN)(6), Auchere, F., Raleiras P., Benson L., Venyaminov S. Y., Tavares P., Moura J. J. G., Moura I., and Rusnak F. , INORGANIC CHEMISTRY, Volume {42}, Number {4}, p.{938-940}, (2003) Abstract

Superoxide reductases catalyze the monovalent reduction of superoxide anion to hydrogen peroxide. Spectroscopic evidence for the formation of a dinuclear cyano-bridged adduct after K3Fe-(CN)(6) oxidation of the superoxide reductases neelaredoxin from Treponema pallidum and desulfoferrodoxin from Desulfovibrio vulgaris was reported. Oxidation with K3Fe(CN)(6) reveals a band in the near-IR with lambda(max) at 1020 nm, coupled with an increase of the iron content by almost 2-fold. Fourier transform infrared spectroscopy provided additional evidence with CN-stretching vibrations at 2095, 2025-2030, and 2047 cm(-1), assigned to a ferrocyanide adduct of the enzyme. Interestingly, the low-temperature electronic paramagnetic resonance (EPR) spectra of oxidized TpNIr reveal at least three different species indicating structural heterogeneity in the coordination environment of the active site Fe ion. Given the likely 6-coordinate geometry of the active site Fe3+ ion in the ferrocyanide adduct, we propose that the rhombic EPR species can serve as a model of a hexacoordinate form of the active site.

2001
Developmen of an electrochemical biosensor for nitrite determination, Almeida, G., Tavares P., Lampreia J., Moura J. J. G., and Moura I. , Journal Of Inorganic Biochemistry, Aug, Volume {86}, Number {1}, p.{121}, (2001) Abstract
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Structure-function studies of cytochrome c peroxidase from ps. nautica, Alves, T., Besson S., Pereira A. S., Pettigrew G. W., Moura J. J. G., and Moura I. , Journal Of Inorganic Biochemistry, Aug, Volume {86}, Number {1}, 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA, p.{122}, (2001) Abstract
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1999
Purification and characterization of a tungsten-containing formate dehydrogenase from Desulfovibrio gigas, Almendra, M. J., Brondino C. D., Gavel O., Pereira A. S., Tavares P., Bursakov S., Duarte R., Caldeira J., Moura J. J. G., and Moura I. , Biochemistry, Volume {38}, Number {49}, p.{16366-16372}, (1999) Abstract

An air-stable formate dehydrogenase (FDH), an enzyme that catalyzes the oxidation of formate to carbon dioxide, was purified from the sulfate reducing organism Desulfovibrio gigas (D. gigas) NCIB 9332. D. gigas FDH is a heterodimeric protein [alpha (92 kDa) and beta (29 kDa) subunits] and contains 7 +/- 1 Fe/protein and 0.9 +/- 0.1 W/protein, Selenium was not detected. The UV/visible absorption spectrum of D, gigas FDH is typical of an iron-sulfur protein. Analysis of pterin nucleotides yielded a content of 1.3 +/- 0.1 guanine monophosphate/mol of enzyme, which suggests a tungsten coordination with two molybdopterin guanine dinucleotide cofactors. Both Mossbauer spectroscopy performed on D. gigas FDH grown in a medium enriched with Fe-57 and EPR studies performed in the native and fully reduced state of the protein confirmed the presence of two [4Fe-4S] clusters. Variable-temperature EPR studies showed the presence of two signals compatible with an atom in a d(1) configuration albeit with an unusual relaxation behavior as compared to the one generally observed for W(V) ions.

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