EPR and Mossbauer spectroscopic studies on enoate reductase,
Caldeira, J., Feicht R., White H., Teixeira M., Moura J. J., Simon H., and Moura I.
, J Biol Chem, Aug 2, Volume 271, Number 31, p.18743-8, (1996)
AbstractEnoate reductase (EC 1.3.1.31) is a protein isolated from Clostridium tyrobutyricum that contains iron, labile sulfide, FAD, and FMN. The enzyme reduces the alpha,beta carbon-carbon double bond of nonactivated 2-enoates and in a reversible way that of 2-enals at the expense of NADH or reduced methyl viologen. UV-visible and EPR potentiometric titrations detect a semiquinone species in redox intermediate states characterized by an isotropic EPR signal at g = 2.0 without contribution at 580 nm. EPR redox titration shows two widely spread mid-point redox potentials (-190 and -350 mV at pH 7. 0), and a nearly stoichiometric amount of this species is detected. The data suggest the semiquinone radical has an anionic nature. In the reduced form, the [Fe-S] moiety is characterized by a single rhombic EPR spectrum, observed in a wide range of temperatures (4. 2-60 K) with g values at 2.013, 1.943, and 1.860 (-180 mV at pH 7.0). The gmax value is low when compared with what has been reported for other iron-sulfur clusters. Mossbauer studies reveal the presence of a [4Fe-4S]+2/+1 center. One of the subcomponents of the spectrum shows an unusually large value of quadrupole splitting (ferrous character) in both the oxidized and reduced states. Substrate binding to the reduced enzyme induces subtle changes in the spectroscopic Mossbauer parameters. The Mossbauer data together with known kinetic information suggest the involvement of this iron-sulfur center in the enzyme mechanism.
ESR studies of cytochrome c3 from Desulfovibrio desulfuricans strain Norway 4: Midpoint potentials of the four haems, and interactions with ferredoxin and colloidal sulphur,
Cammack, R., Fauque G., Moura J. J. G., and Legall J.
, Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology, Volume 784, Number 1, p.68-74, (1984)
Abstractn/a
The effect of pH on Marinobacter hydrocarbonoclasticus denitrification pathway and nitrous oxide reductase,
Carreira, C., Nunes R. F., Mestre O., Moura I., and Pauleta S. R.
, J Biol Inorg Chem, Volume 25, p.927, (2020)
The effect of the sixth sulfur ligand in the catalytic mechanism of periplasmic nitrate reductase,
Cerqueira, N. M., Gonzalez P. J., Brondino C. D., Romao M. J., Romao C. C., Moura I., and Moura J. J.
, J Comput Chem, Nov 30, Volume 30, Number 15, p.2466-84, (2009)
AbstractThe catalytic mechanism of nitrate reduction by periplasmic nitrate reductases has been investigated using theoretical and computational means. We have found that the nitrate molecule binds to the active site with the Mo ion in the +6 oxidation state. Electron transfer to the active site occurs only in the proton-electron transfer stage, where the Mo(V) species plays an important role in catalysis. The presence of the sulfur atom in the molybdenum coordination sphere creates a pseudo-dithiolene ligand that protects it from any direct attack from the solvent. Upon the nitrate binding there is a conformational rearrangement of this ring that allows the direct contact of the nitrate with Mo(VI) ion. This rearrangement is stabilized by the conserved methionines Met141 and Met308. The reduction of nitrate into nitrite occurs in the second step of the mechanism where the two dimethyl-dithiolene ligands have a key role in spreading the excess of negative charge near the Mo atom to make it available for the chemical reaction. The reaction involves the oxidation of the sulfur atoms and not of the molybdenum as previously suggested. The mechanism involves a molybdenum and sulfur-based redox chemistry instead of the currently accepted redox chemistry based only on the Mo ion. The second part of the mechanism involves two protonation steps that are promoted by the presence of Mo(V) species. Mo(VI) intermediates might also be present in this stage depending on the availability of protons and electrons. Once the water molecule is generated only the Mo(VI) species allow water molecule dissociation, and, the concomitant enzymatic turnover.
Electronic structure description of the mu(4)-sulfide bridged tetranuclear Cu(Z) center in N(2)O reductase,
Chen, P., DeBeer George S., Cabrito I., Antholine W. E., Moura J. J., Moura I., Hedman B., Hodgson K. O., and Solomon E. I.
, J Am Chem Soc, Feb 6, Volume 124, Number 5, p.744-5, (2002)
AbstractSpectroscopy coupled with density functional calculations has been used to define the spin state, oxidation states, spin distribution, and ground state wave function of the mu4-sulfide bridged tetranuclear CuZ cluster of nitrous oxide reductase. Initial insight into the electronic contribution to N2O reduction is developed, which involves a sigma superexchange pathway through the bridging sulfide.
Electrochemical studies on c-type cytochromes at microelectrodes,
Correia dos Santos, M. M., Paes de Sousa P. M., Simões Gonçalves M. L., Lopes H., Moura I., and Moura J. J. G.
, Journal of Electroanalytical Chemistry, Volume 464, Number 1, p.76-84, (1999)
Abstractn/a
Electrochemical studies of rubredoxin from Desulfovibrio vulgaris at modified electrodes,
Correia dos Santos, M. M., Paes de Sousa P. M., Simões Gonçalves M. L., Ascenso C., Moura I., and Moura J. J. G.
, Journal of Electroanalytical Chemistry, Volume 501, Number 1–2, p.173-179, (2001)
Abstractn/a
Expression of Desulfovibrio gigas desulforedoxin in Escherichia coli. Purification and characterization of mixed metal isoforms,
Czaja, C., Litwiller R., Tomlinson A. J., Naylor S., Tavares P., Legall J., Moura J. J., Moura I., and Rusnak F.
, J Biol Chem, Sep 1, Volume 270, Number 35, p.20273-7, (1995)
AbstractThe dsr gene from Desulfovibrio gigas encoding the nonheme iron protein desulforedoxin was cloned using the polymerase chain reaction, expressed in Escherichia coli, and purified to homogeneity. The physical and spectroscopic properties of the recombinant protein resemble those observed for the native protein isolated from D. gigas. These include an alpha 2 tertiary structure, the presence of bound iron, and absorbance maxima at 370 and 506 nm in the UV/visible spectrum due to ligand-to-iron charge transfer bands. Low temperature electron paramagnetic resonance studies confirm the presence of a high-spin ferric ion with g values of 7.7, 5.7, 4.1, and 1.8. Interestingly, E. coli produced two forms of desulforedoxin containing iron. One form was identified as a dimer with the metal-binding sites of both subunits occupied by iron while the second form contained equivalent amounts of iron and zinc and represents a dimer with one subunit occupied by iron and the second with zinc.