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2000
A novel type of catalytic copper cluster in nitrous oxide reductase, Brown, K., Tegoni M., Prudencio M., Pereira A. S., Besson S., Moura J. J., Moura I., and Cambillau C. , Nat Struct Biol, Mar, Volume 7, Number 3, p.191-5, (2000) AbstractWebsite

Nitrous oxide (N20) is a greenhouse gas, the third most significant contributor to global warming. As a key process for N20 elimination from the biosphere, N20 reductases catalyze the two-electron reduction of N20 to N2. These 2 x 65 kDa copper enzymes are thought to contain a CuA electron entry site, similar to that of cytochrome c oxidase, and a CuZ catalytic center. The copper anomalous signal was used to solve the crystal structure of N20 reductase from Pseudomonas nautica by multiwavelength anomalous dispersion, to a resolution of 2.4 A. The structure reveals that the CuZ center belongs to a new type of metal cluster, in which four copper ions are liganded by seven histidine residues. N20 binds to this center via a single copper ion. The remaining copper ions might act as an electron reservoir, assuring a fast electron transfer and avoiding the formation of dead-end products.

A novel protein-bound copper - Molybdenum cluster, George, G. N., Pickering I. J., Yu E. Y., Prince R. C., Bursakov S. A., Gavel O. Y., Moura I., and Moura J. J. G. , Journal of the American Chemical Society, Aug 30, Volume 122, Number 34, p.8321-8322, (2000) AbstractWebsite
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1998
NMR determination of the global structure of the 113Cd derivative of desulforedoxin: investigation of the hydrogen bonding pattern at the metal center, Goodfellow, B. J., Rusnak F., Moura I., Domke T., and Moura J. J. , Protein Sci, Apr, Volume 7, Number 4, p.928-37, (1998) AbstractWebsite

Desulforedoxin (Dx) is a simple homodimeric protein isolated from Desulfovibrio gigas (Dg) containing a distorted rubredoxin-like center with one iron coordinated by four cysteinyl residues (7.9 kDa with 36 amino acids per monomer). In order to probe the geometry and the H-bonding at the active site of Dx, the protein was reconstituted with 113Cd and the solution structure determined using 2D NMR methods. The structure of this derivative was initially compared with the NMR solution structure of the Zn form (Goodfellow BJ et al., 1996, J Biol Inorg Chem 1:341-353). Backbone amide protons for G4, D5, G13, L11 NH, and the Q14 NH side-chain protons, H-bonded in the X-ray structure, were readily exchanged with solvent. Chemical shift differences observed for amide protons near the metal center confirm the H-bonding pattern seen in the X-ray model (Archer M et al., 1995, J Mol Biol 251:690-702) and also suggest that H-bond lengths may vary between the Fe, Zn, and 113Cd forms. The H-bonding pattern was further probed using a heteronuclear spin echo difference (HSED) experiment; the results confirm the presence of NH-S H-bonds inferred from D2O exchange data and observed in the NMR family of structures. The presence of "H-bond mediated" coupling in Dx indicates that the NH-S H-bonds at the metal center have significant covalent character. The HSED experiment also identified an intermonomer "through space" coupling for one of the L26 methyl groups, indicating its proximity to the 113Cd center in the opposing monomer. This is the first example of an intermonomer "through space" coupling. Initial structure calculations produced subsets of NMR families with the S of C28 pointing away from or toward the L26 methyl: only the subset with the C28 sulfur pointing toward the L26 methyl could result in a "through space" coupling. The HSED result was therefore included in the structure calculations. Comparison of the Fe, Zn, and 113Cd forms of Dx suggests that the geometry of the metal center and the global fold of the protein does not vary to any great extent, although the H-bond network varies slightly when Cd is introduced. The similarity between the H-bonding pattern seen at the metal center in Dx, Rd (including H-bonded and through space-mediated coupling), and many zinc-finger proteins suggests that these H-bonds are structurally vital for stabilization of the metal centers in these proteins.

1997
Nitrate and nitrite utilization in sulfate-reducing bacteria, Moura, I., Bursakov S., Costa C., and Moura J. J. , Anaerobe, Oct, Volume 3, Number 5, p.279-90, (1997) AbstractWebsite
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1992
The nickel site in active Desulfovibrio baculatus [NiFeSe] hydrogenase is diamagnetic. Multifield saturation magnetization measurement of the spin state of Ni(II), Wang, C. P., Franco R., Moura J. J., Moura I., and Day E. P. , J Biol Chem, Apr 15, Volume 267, Number 11, p.7378-80, (1992) AbstractWebsite

The magnetic properties of the nickel(II) site in active Desulfovibrio baculatus (DSM 1743) [NiFeSe] hydrogenase have been measured using the multifield saturation magnetization technique. The periplasmic [NiFeSe] hydrogenase was isolated from bacteria grown in excess selenium in the presence of 57Fe. Saturation magnetization data were collected at three fixed fields (1.375, 2.75, 5.5 tesla) over the temperature range from 2 to 100 K. Mossbauer and EPR spectroscopies were used to characterize the magnetic state of the two [4Fe-4S] clusters of the enzyme and to quantitate the small amounts of iron impurities present in the sample. The nickel(II) site was found to be diamagnetic (low spin, S = 0). In combination with recent results from extended x-ray absorption fine structure studies, this magnetic state indicates that the nickel(II) site of active D. baculatus [NiFeSe] hydrogenase is five-coordinate.

NMR and EPR studies on a monoheme cytochrome c550 isolated from Bacillus halodenitrificans, Saraiva, Lígia M., Denariaz Gerard, Liu Ming- Y., Payne William J., Legall Jean, and Moura Isabel , European Journal of Biochemistry, Volume 204, Number 3, p.1131-1139, (1992) AbstractWebsite

A c-type monoheme ferricytochrome c550 (9.6 kDa) was isolated from cells of Bacillus halodenitrificans sp.nov., grown anaerobically as a denitrifier. The visible absorption spectrum indicates the presence of a band at 695 nm characteristic of heme–methionine coordination. The mid-point redox potential was determined at several pH values by visible spectroscopy. The redox potential at pH 7.6 is 138 mV. When studied by 1H-NMR spectroscopy as a function of pH, the spectrum shows a pH dependence with pKa values of 6.0 and 11.0. According to these pKa values, three forms designated as I, II and III can be attributed to cytochrome c550. The first pKa is probably associated with protonation of the propionate groups. The second pKa value introduces a larger effect in the 1H-NMR spectrum and is probably due to the ionisation of the axial histidine. Studies of temperature variation of the 1H-NMR spectra for both the ferrous and ferri forms of the cytochrome were performed. Heme meso protons, the heme methyl groups, the thioether protons, two protons from a propionate and the methylene protons from the axial methionine were identified in the reduced form. The heme methyl resonances of the ferri form were also assigned. EPR spectroscopy was also used to probe the ferric heme environment. A signal at gmax∼ 3.5 at pH 7.5 was observed indicating an almost axial heme environment. At higher pH values the signal at gmax∼ 3.5 converts mainly to a signal at g∼ 2.96. The pKa associated with this change is around 11.3. The N-terminal sequence of this cytochrome was determined and compared with known amino acid sequences of other cytochromes.

1988
NICKEL-CONTAINING HYDROGENASES, Moura, J. J. G., Moura I., Teixeira M., Xavier A. V., Fauque G. D., and Legall J. , Metal Ions in Biological Systems, 1988, Volume 23, p.285-314, (1988) AbstractWebsite
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1987
Nickel-[iron-sulfur]-selenium-containing hydrogenases from Desulfovibrio baculatus (DSM 1743). Redox centers and catalytic properties, Teixeira, M., Fauque G., Moura I., Lespinat P. A., Berlier Y., Prickril B., Peck, H. D. Jr., Xavier A. V., Legall J., and Moura J. J. , Eur J Biochem, Aug 17, Volume 167, Number 1, p.47-58, (1987) AbstractWebsite

The hydrogenase from Desulfovibrio baculatus (DSM 1743) was purified from each of three different fractions: soluble periplasmic (wash), soluble cytoplasmic (cell disruption) and membrane-bound (detergent solubilization). Plasma-emission metal analysis detected in all three fractions the presence of iron plus nickel and selenium in equimolecular amounts. These hydrogenases were shown to be composed of two non-identical subunits and were distinct with respect to their spectroscopic properties. The EPR spectra of the native (as isolated) enzymes showed very weak isotropic signals centered around g approximately 2.0 when observed at low temperature (below 20 K). The periplasmic and membrane-bound enzymes also presented additional EPR signals, observable up to 77 K, with g greater than 2.0 and assigned to nickel(III). The periplasmic hydrogenase exhibited EPR features at 2.20, 2.06 and 2.0. The signals observed in the membrane-bound preparations could be decomposed into two sets with g at 2.34, 2.16 and approximately 2.0 (component I) and at 2.33, 2.24, and approximately 2.0 (component II). In the reduced state, after exposure to an H2 atmosphere, all the hydrogenase fractions gave identical EPR spectra. EPR studies, performed at different temperatures and microwave powers, and in samples partially and fully reduced (under hydrogen or dithionite), allowed the identification of two different iron-sulfur centers: center I (2.03, 1.89 and 1.86) detectable below 10 K, and center II (2.06, 1.95 and 1.88) which was easily saturated at low temperatures. Additional EPR signals due to transient nickel species were detected with g greater than 2.0, and a rhombic EPR signal at 77 K developed at g 2.20, 2.16 and 2.0. This EPR signal is reminiscent of the Ni-signal C (g at 2.19, 2.14 and 2.02) observed in intermediate redox states of the well characterized Desulfovibrio gigas hydrogenase (Teixeira et al. (1985) J. Biol. Chem. 260, 8942]. During the course of a redox titration at pH 7.6 using H2 gas as reductant, this signal attained a maximal intensity around -320 mV. Low-temperature studies of samples at redox states where this rhombic signal develops (10 K or lower) revealed the presence of a fast-relaxing complex EPR signal with g at 2.25, 2.22, 2.15, 2.12, 2.10 and broad components at higher field. The soluble hydrogenase fractions did not show a time-dependent activation but the membrane-bound form required such a step in order to express full activity.(ABSTRACT TRUNCATED AT 400 WORDS)

1985
Nickel X-ray absorption spectroscopy of Desulvovibrio gigas hydrogenase, Scott, R. A., Czechowski M., Dervartanian D. V., Legall J., Peck Jr H. D., and Moura I. , Rev Portuguesa de Química, Volume 27, p.67-70, (1985) Abstract
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1984
Nuclear-magnetic-resonance studies of Desulfuromonas acetoxidans cytochrome c551.5 (c7), Moura, J. G., Moore G. R., Williams R. J., Probst I., Legall J., and Xavier A. V. , Eur J Biochem, Nov 2, Volume 144, Number 3, p.433-40, (1984) AbstractWebsite

1H nuclear magnetic resonance (NMR) spectroscopy has been used to examine cytochrome c551.5 (c7) from the sulfur reducer, Desulfuromonas acetoxidans. This protein contains three hemes. Two stable oxidation states (the fully oxidized and the fully reduced) as well as intermediate oxidation states were studied. The axial ligands of the iron were found to be neutral histidines. The redox properties of cytochrome c7 were examined and good quantitative agreement found between the NMR results and previously reported redox potential measurements. The properties of cytochrome c7 are discussed together with those of the homologous tetraheme cytochromes c3 isolate from sulfate-reducing bacteria.

NMR and electron-paramagnetic-resonance studies of a dihaem cytochrome from Pseudomonas stutzeri (ATCC 11607) (cytochrome c peroxidase), Villalain, J., Moura I., Liu M. C., Payne W. J., Legall J., Xavier A. V., and Moura J. J. , Eur J Biochem, Jun 1, Volume 141, Number 2, p.305-12, (1984) AbstractWebsite

A dihaem cytochrome (Mr 37 400) with cytochrome c peroxidase activity was purified from Pseudomonas stutzeri (ATCC 11 607). The haem redox potentials are far apart: one of the haems is completely ascorbate-reducible and the other is only reduced by dithionite. The coordination, spin states and redox properties of the covalently bound haems were probed by visible, NMR and electron paramagnetic resonance (EPR) spectroscopies in three oxidation states. In the oxidized state, the low-temperature EPR spectrum of the native enzyme is a complex superimposition of three components: (I) a low-spin haem indicating a histidinyl-methionyl coordination; (II) a low-spin haem indicating a histidinyl-histidinyl coordination; and (III) a minor high-spin haem component. At room temperature, NMR and optical studies indicate the presence of high-spin and low-spin haems, suggesting that for one of the haems a high-spin to low-spin transition is observed when temperature is decreased. In the half-reduced state, the component I (high redox potential) of the EPR spectrum disappears and induces a change in the g-values and linewidth of component II; the high-spin component II is no longer detected at low temperature. Visible and NMR studies reveal the presence of a high-spin ferric and a low-spin (methionyl-coordinated) ferrous state. The NMR data fully support the haem-haem interaction probed by EPR. In the reduced state, the NMR spectrum indicates that the low-potential haem is high-spin ferrous.

NMR studies of a dihaem cytochrome from Pseudomonas perfectomarinus (ATCC 14405), Moura, I., Liu M. C., Legall J., Peck, H. D. Jr., Payne W. J., Xavier A. V., and Moura J. J. , Eur J Biochem, Jun 1, Volume 141, Number 2, p.297-303, (1984) AbstractWebsite

Pseudomonas perfectomarinus (ATCC 14405) dihaem cytochrome c552 was studied by 300-MHz proton magnetic resonance. Some of the haem resonances were assigned in the fully reduced and fully oxidized states. No evidence was found for methionine haem axial coordination. The oxidation-reduction equilibrium was studied in detail. Due to the large difference in mid-point redox potential between the two haems (+174 mV, for haem II and -180 mV for haem I) an intermediate oxidation state could be obtained containing reduced haem I and oxidized haem II. In this way the total paramagnetic shift at different oxidation levels could be decomposed in the intrinsic and extrinsic contributions. It was found that the two haems interact. The rate of electron exchange is slow on the NMR time scale. The redox equilibria are discussed for four possible redox species in solution.

NMR studies of electron transfer mechanisms in a protein with interacting redox centres: Desulfovibrio gigas cytochrome c3, Santos, H., Moura J. J., Moura I., Legall J., and Xavier A. V. , Eur J Biochem, Jun 1, Volume 141, Number 2, p.283-96, (1984) AbstractWebsite

The proton NMR spectra of the tetrahaem cytochrome c3 from Desulfovibrio gigas were examined while varying the pH and the redox potential. The analysis of the NMR reoxidation pattern was based on a model for the electron distribution between the four haems that takes into account haem-haem redox interactions. The intramolecular electron exchange is fast on the NMR time scale (larger than 10(5) s-1). The NMR data concerning the pH dependence of the chemical shift of haem methyl resonances in different oxidation steps and resonance intensities are not compatible with a non-interacting model and can be explained assuming a redox interaction between the haems. A complete analysis at pH* = 7.2 and 9.6, shows that the haem-haem interacting potentials cover a range from -50 mV to +60 mV. The midpoint redox potentials of some of the haems, as well as some of their interacting potentials, are pH-dependent. The physiological relevance of the modulation of the haem midpoint redox potentials by both the pH and the redox potential of the solution is discussed.

Nickel - a redox catalytic site in hydrogenase, Moura, J. J. G., Teixeira M., Moura I., Xavier A. V., and Legall J. , Journal of Molecular Catalysis, Volume 23, Number 2–3, p.303-314, (1984) AbstractWebsite
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Nuclear-magnetic-resonance studies of Desulfuromonas acetoxidans cytochrome c551.5 (c7), Moura, José J. G., Moore Geoffrey R., Williams Robert J. P., Probst Irmelin, Legall Jean, and Xavier António V. , European Journal of Biochemistry, Volume 144, Number 3, p.433-440, (1984) AbstractWebsite

1H nuclear magnetic resonance (NMR) spectroscopy has been used to examine cytochrome c551.5 (c7) from the sulfur reducer, Desulfuromonas acetoxidans. This protein contains three hemes. Two stable oxidation states (the fully oxidized and the fully reduced) as well as intermediate oxidation states were studied. The axial ligands of the iron were found to be neutral histidines. The redox properties of cytochrome c7 were examined and good quantitative agreement found between the NMR results and previously reported redox potential measurements. The properties of cytochrome c7 are discussed together with those of the homologous tetraheme cytochromes c3 isolate from sulfate-reducing bacteria.

1983
Nickel containing hydrogenases, Xavier, A. V., Teixeira M., Moura I., Moura J. J. G., and Legall J. , Inorganica Chimica Acta, Volume 79, p.13-14, (1983) AbstractWebsite
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1982
NMR redox studies of Desulfovibrio vulgaris Cytochrome c3. Electron transfer mechanisms, Moura, J. J., Santos H., Moura I., Legall J., Moore G. R., Williams R. J., and Xavier A. V. , Eur J Biochem, Sep, Volume 127, Number 1, p.151-5, (1982) AbstractWebsite

The 300-MHz proton NMR spectra of the tetrahaem cytochrome c3 from Desulfovibrio vulgaris were examined while varying the pH and the redox potential. The analysis of the complete NMR reoxidation pattern was done taking into account all the 16 redox states that can be present in the redox titration of a tetra-redox-center molecule. A network of saturation transfer experiments performed at different oxidation stages, between the fully reduced and the fully oxidized states, allowed the observation of different resonances for some of the haem methyl groups. In the present experimental conditions, some of the haems show a fast intramolecular electron exchange rate, but the intermolecular electron exchange is always slow. In intermediate reoxidation stages, large shifts of the resonances of some haem methyl groups were observed upon changing the pH. These shifts are discussed in terms of a pH dependence of the haem midpoint redox potentials. The physiological relevance of this pH dependence is discussed.

1981
NOVEL STRUCTURES IN IRON-SULFUR PROTEINS, Xavier, A. V., Moura J. J. G., and Moura I. , Structure and Bonding, 1981, Volume 43, p.187-213, (1981) AbstractWebsite
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Novel structures in iron-sulfur proteinsBonding Problems, Xavier, António, Moura José, and Moura Isabel , Volume 43, p.187-213, (1981) Abstract
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1978
NMR studies of electron carrier proteins from sulphate reducing bacteria, Xavier, A. V., and Moura J. J. , Biochimie, Volume 60, Number 3, p.327-38, (1978) AbstractWebsite

The sulphate-reducing bacteria have a complex electron transfer system which leads to the reduction of sulphate by oxidation of either organic substrates or molecular hydrogen. These bacteria can either produce or consume molecular hydrogen. The central part of this electron pathway for Desulovibrio gigas is constituted by hydrogenase (3 X (4Fe-4S)). cytochrome c3 (4 haems with different redox potentials) and a one (4Fe-4S) cluster ferredoxin. This ferredoxin is isolated in different oligomeric forms, which stabilize different oxidation states and have different physiological roles; the trimer FdI being involved in the production of H2 and the tetramer FdII being more efficient for the consumption of H2. The presence of intrinsic probes (the iron ions) in these proteins is particularly helpful for structural studies using NMR spectroscopy. These studies allowed a characterization of the oxidation states used by the different oligomers of the ferredoxin and obtaintion of structural information on multi-haem cytochromes (c3 and c7). NMR is also suitable to study protein-protein interaction. The study of the complex formed between FdII and cytochrome c3 has shown that there is an alteration of the kinetics of electron transfer upon complexation.

1977
NMR characterization of three forms of ferredoxin from Desulphovibrio gigas, a sulphate reducer, Moura, J. J., Xavier A. V., Bruschi M., and Gall J. L. , Biochim Biophys Acta, Feb 7, Volume 459, Number 2, p.278-89, (1977) AbstractWebsite

A NMR and magnetic susceptibility study of the oxidized and reduced states of three different oligomers (forms) of a [4Fe-4S] ferrodoxin protein from Desulphovibrio gigas, FdI, FdI', and FdII was carried out. FdI and FdI' are different trimers and FdII a tetramer of the same basic subunit. A probable assignment of the contact shifted resonances is indicated. Since the temperature dependences of the contact shifted responances associated with each [4Fe-4S] are not all similar a delocalized model for the spin densities on the 4Fe does not apply. The exchange rate between oxidized and reduced states is slow on the NMR time scale. The three oligomers are not magnetically equivalent. Using the "three state hypothesis" terminology it is shown that FdIox is predominantly in the C2- state and changes upon reduction into the C3- state, while FdIIox is in the C- state and changes into the C2- state. FdI' does not easily fit into this classification. This study shows a similarity of magnetic behaviour between FdI and bacterial ferredoxins (e.g. Bacillus polymyxa) and between FdII and HiPIP from Chromatium sp. The influence of the quaternary structure on the stabilization of the different oxidation states of ferredoxins as well as on their redox potentials is discussed.