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Huynh BH, Patil DS, Moura I, Teixeira M, Moura JJ, DerVartanian DV, Czechowski MH, Prickril BC, Peck HD, LeGall J. On the active sites of the [NiFe] hydrogenase from Desulfovibrio gigas. Mössbauer and redox-titration studies. J Biol Chem 1987; 262:795-800. [PMID: 3027068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The [NiFe] hydrogenase isolated from Desulfovibrio gigas was poised at different redox potentials and studied by Mössbauer spectroscopy. The data firmly establish that this hydrogenase contains four prosthetic groups: one nickel center, one [3Fe-xS], and two [4Fe-4S] clusters. In the native enzyme, both the nickel and the [3Fe-xS] cluster are EPR-active. At low temperature (4.2 K), the [3Fe-xS] cluster exhibits a paramagnetic Mössbauer spectrum typical for oxidized [3Fe-xS] clusters. At higher temperatures (greater than 20 K), the paramagnetic spectrum collapses into a quadrupole doublet with parameters magnitude of delta EQ magnitude of = 0.7 +/- 0.06 mm/s and delta = 0.36 +/- 0.06 mm/s, typical of high-spin Fe(III). The observed isomer shift is slightly larger than those observed for the three-iron clusters in D. gigas ferredoxin II (Huynh, B. H., Moura, J. J. G., Moura, I., Kent, T. A., LeGall, J., Xavier, A. V., and Münck, E. (1980) J. Biol. Chem. 255, 3242-3244) and in Azotobacter vinelandii ferredoxin I (Emptage, M. H., Kent, T. A., Huynh, B. H., Rawlings, J., Orme-Johnson, W. H., and Münck, E. (1980) J. Biol. Chem. 255, 1793-1796) and may indicate a different iron coordination environment. When D. gigas hydrogenase is poised at potentials lower than -80 mV (versus normal hydrogen electrode), the [3Fe-xS] cluster is reduced and becomes EPR-silent. The Mössbauer data indicate that the reduced [3Fe-xS] cluster remains intact, i.e. it does not interconvert into a [4Fe-4S] cluster. Also, the electronic properties of the reduced [3Fe-xS] cluster suggest that it is magnetically isolated from the other paramagnetic centers.
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Huynh BH, Patil DS, Moura I, Teixeira M, Moura JJ, DerVartanian DV, Czechowski MH, Prickril BC, Peck HD, LeGall J. On the active sites of the [NiFe] hydrogenase from Desulfovibrio gigas. Mössbauer and redox-titration studies. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(19)75856-6] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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53
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Matzanke BF, Ecker DJ, Yang TS, Huynh BH, Müller G, Raymond KN. Escherichia coli iron enterobactin uptake monitored by Mössbauer spectroscopy. J Bacteriol 1986; 167:674-80. [PMID: 2942533 PMCID: PMC212942 DOI: 10.1128/jb.167.2.674-680.1986] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Iron uptake by Escherichia coli under aerobic conditions of iron deficiency is mediated by a highly stable ferric enterobactin [Fe(ent)3-] siderophore complex. Mössbauer spectroscopy has been used to monitor the fate of the iron as 57Fe(ent) was taken up by the cells. Osmotic shock experiments were used to distinguish between the iron present in the periplasmic space and that in the cytoplasm of the cell. Iron delivery by a synthetic analog of enterobactin, 1,3,5-N,N',N''- tris-(2,3-dihydroxybenzoyl)triaminomethylbenzene (MECAM), was also studied. Although Fe-MECAM was transported at the same rate as was Fe(ent) across the outer membrane and was apparently accumulated in the periplasmic space, the subsequent behaviors of Fe(ent) and Fe-MECAM were very different. After more than 30 min, a major fraction of the iron originally absorbed as ferric enterobactin appeared as Fe(II), apparently in the cytoplasm of the cell. However, little iron was delivered to the cytoplasm by the MECAM complex. The differences in specificity of these two stages of iron uptake by E. coli are discussed.
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Patil DS, Czechowski MH, Huynh BH, LeGall J, Peck HD, DerVartanian DV. A reversible effect of low carbon monoxide concentrations on the EPR spectra of the periplasmic hydrogenase from Desulfovibrio vulgaris. Biochem Biophys Res Commun 1986; 137:1086-93. [PMID: 3015136 DOI: 10.1016/0006-291x(86)90336-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The effect of low concentrations of CO (0.93 - 5.58 microM) on the EPR spectrum of the periplasmic non-heme iron hydrogenase from D. vulgaris has been investigated. The "g = 2.06" EPR signal is maximally induced (0.94 spin/molecule) at 46.5 microM CO and partial induction of the EPR signal could be observed at 0.93 microM CO. This effect is reversed by removal of the CO or irradiation of the hydrogenase with white light.
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Teixeira M, Moura I, Xavier AV, Huynh BH, DerVartanian DV, Peck HD, LeGall J, Moura JJ. Electron paramagnetic resonance studies on the mechanism of activation and the catalytic cycle of the nickel-containing hydrogenase from Desulfovibrio gigas. J Biol Chem 1985; 260:8942-50. [PMID: 2991227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Desulfovibrio gigas hydrogenase (EC 1.12.2.1) is a complex enzyme containing one nickel, one 3Fe, and two [Fe4S4] clusters (Teixeira, M., Moura, I., Xavier, A. V., Der Vartanian, D. V., LeGall, J., Peck, H. D., Jr., Huynh, B. H., and Moura, J. J. G. (1983) Eur. J. Biochem. 130, 481-484). This hydrogenase belongs to a class of enzymes that are inactive "as isolated" (the so-called "oxygen-stable hydrogenases") and must go through an activation process in order to express full activity. The state of characterization of the active centers of the enzyme as isolated prompted us to do a detailed analysis of the redox patterns, activation profile, and catalytic redox cycle of the enzyme in the presence of either the natural substrate (H2) or chemical reductants. The effect of natural cofactors, as cytochrome C3, was also studied. Special focus was given to the intermediate redox species generated during the catalytic cycle of the enzyme and to the midpoint redox potentials associated. The available information is discussed in terms of a "working hypothesis" for the mechanism of the [NiFe] hydrogenases from sulfate reducing organisms in the context of activation process and catalytic cycle.
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56
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Teixeira M, Moura I, Xavier AV, Huynh BH, DerVartanian DV, Peck HD, LeGall J, Moura JJ. Electron paramagnetic resonance studies on the mechanism of activation and the catalytic cycle of the nickel-containing hydrogenase from Desulfovibrio gigas. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(17)39440-1] [Citation(s) in RCA: 92] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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57
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Huynh BH, Kang L, DerVartanian DV, Peck HD, LeGall J. Characterization of a sulfite reductase from Desulfovibrio vulgaris. Evidence for the presence of a low-spin siroheme and an exchange-coupled siroheme-[4Fe-4S] unit. J Biol Chem 1984; 259:15373-6. [PMID: 6096368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
We have studied a low-molecular-weight (Mr = 27,200) sulfite reductase from Desulfovibrio vulgaris (Hildenborough, NCIB 8303) with Mössbauer, EPR, and chemical techniques. This sulfite reductase was found to contain one siroheme and one [4Fe-4S] cluster. As purified, the siroheme is low-spin ferric (S = 1/2) which exhibits characteristic EPR resonances at g = 2.44, 2.36, and 1.77. At 150 K, the observed Mössbauer parameters, delta EQ = 2.49 +/- 0.02 mm/s and delta = 0.31 +/- 0.02 mm/s, for the siroheme are typical for low-spin ferric complexes. The [4Fe-4S] cluster is in the 2+ state. The Mössbauer parameters, delta EQ = 0.95 +/- 0.02 mm/s and delta = 0.38 +/- 0.02 mm/s, for the cluster are almost identical to those observed for the [4Fe-4S]2+ cluster in the hemoprotein subunit of the sulfite reductase from Escherichia coli. Similar to the hemoprotein subunit of E. coli sulfite reductase, low-temperature Mössbauer spectra of D. vulgaris sulfite reductase recorded with weak and strong applied fields also show evidence for an exchange-coupled siroheme-[4Fe-4S] unit.
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58
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Wang G, Benecky MJ, Huynh BH, Cline JF, Adams MW, Mortenson LE, Hoffman BM, Münck E. Mössbauer and electron nuclear double resonance study of oxidized bidirectional hydrogenase from Clostridium pasteurianum W5. J Biol Chem 1984; 259:14328-31. [PMID: 6094552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The bidirectional hydrogenase from Clostridium pasteurianum W5 is an iron-sulfur protein containing approximately 12 Fe atoms and 12 labile sulfides. We have studied oxidized samples of the enzyme with Mössbauer and electron nuclear double resonance (ENDOR) spectroscopy to elucidate the nature of the center that gives rise to the EPR signal with principal g-values at 2.10, 2.04, and 2.01. The g = 2.10 center exhibits two well-resolved 57Fe ENDOR resonances. One is isotropic with A1 = 9.5 MHz; the other is nearly isotropic with A2 = 17 MHz. These magnetic hyperfine coupling constants are substantially (approximately 50%) smaller than those observed for [2Fe-2S], [3Fe-4S], and [4Fe-4S] clusters. The Mössbauer and ENDOR data, taken together, suggest that the g = 2.10 center contains at least two but not more than four iron atoms. Comparison of our data with recent results reported for Escherichia coli sulfite reductase and the ferricyanide-treated [4Fe-4S] cluster from Azotobacter vinelandii ferredoxin I suggests that the g = 2.10 center may possibly be formed, by oxidation, from a structure with a [4Fe-4S] core. The Mössbauer spectra give evidence that at least 8 of the 12 Fe atoms of oxidized hydrogenase are organized in two ferredoxin-type [4Fe-4S] clusters, supporting conclusions derived previously from EPR studies of the reduced enzyme.
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Wang G, Benecky MJ, Huynh BH, Cline JF, Adams MW, Mortenson LE, Hoffman BM, Münck E. Mössbauer and electron nuclear double resonance study of oxidized bidirectional hydrogenase from Clostridium pasteurianum W5. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(17)42596-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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60
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Huynh BH, Czechowski MH, Krüger HJ, DerVartanian DV, Peck HD, LeGall J. Desulfovibrio vulgaris hydrogenase: a nonheme iron enzyme lacking nickel that exhibits anomalous EPR and Mössbauer spectra. Proc Natl Acad Sci U S A 1984; 81:3728-32. [PMID: 6328525 PMCID: PMC345292 DOI: 10.1073/pnas.81.12.3728] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
A purification procedure for the periplasmic hydrogenase from Desulfovibrio vulgaris ( Hildenborough , National Collection of Industrial Bacteria 8303) is reported. The purified hydrogenase has a specific activity of 4800 units per mg of protein. Plasma emission studies reveal that this highly active hydrogenase is free of nickel and contains 11 (+/- 1) nonheme iron atoms per molecule. A combined EPR and Mössbauer study indicates that the majority of the iron atoms are bound in the form of iron- sulfur clusters. Two ferredoxin-type [4Fe-4S] clusters have been identified that exhibit normal EPR and Mössbauer parameters; however, no trace of 3Fe cluster is detected by the Mössbauer measurement. In the presence of oxidants, cytochrome c3, and CO, anomalous EPR and Mössbauer spectra indicative of atypical nonheme iron centers are observed.
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61
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Arciero DM, Lipscomb JD, Huynh BH, Kent TA, Münck E. EPR and Mössbauer studies of protocatechuate 4,5-dioxygenase. Characterization of a new Fe2+ environment. J Biol Chem 1983; 258:14981-91. [PMID: 6317682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Protocatechuate 4,5-dioxygenase from Pseudomonas testosteroni has been purified to homogeneity and crystallized. The iron containing, extradiol dioxygenase is shown to be composed of two subunit types (alpha, Mr = 17,700 and beta, Mr = 33,800) in a 1:1 ratio; such a composition has not been observed for other extradiol dioxygenases. The 4.2 K Mössbauer spectrum of native protocatechuate 4,5-dioxygenase prepared from cells grown in 57Fe-enriched media consists of a doublet with quadrupole splitting, delta EQ = 2.22 mm/s, and isomer shift delta Fe = 1.28 mm/s, demonstrating a high spin Fe2+ site. These parameters, and the temperature dependence of delta EQ, are unique among enzymes but are strikingly similar to those reported for the reaction center of the photosynthetic bacterium Rhodopseudomonas sphaeroides R-26, suggesting very similar ligand environments. The Fe2+ of protocatechuate 4,5-dioxygenase can be oxidized, for instance by H2O2, to yield high spin Fe3+ with EPR g values around g = 6 (and g = 4.3). In the oxidized state, protocatechuate 4,5-dioxygenase is inactive; the iron, however, can be rereduced by ascorbate to yield active enzyme. Our data suggest that protocatechuate binds to Fe2+; the spectra indicate that the ligand binding is heterogenous. The Mössbauer spectra observed here are fundamentally different from those reported earlier (Zabinski, R., Münck, E., Champion, P., and Wood, J. M. (1972) Biochemistry 11, 3212-3219). The spectra of the earlier (reconstituted) preparations, which had substantially lower specific activities, probably reflect adventitiously bound Fe3+. We discuss here how adventitiously bound iron can be identified and removed. The Fe2+ which is present in native protocatechuate 4,5-dioxygenase and its complexes with substrates and inhibitors reacts quantitatively with nitric oxide to produce a species with electronic spin S = 3/2. The EPR and Mössbauer spectra of these complexes compare favorably with EDTA . Fe(II) . NO. We have studied the latter complex extensively and have analyzed the Mössbauer spectra with an S = 3/2 spin Hamiltonian. EPR spectra show that protocatechuate 4,5-dioxygenase-NO complexes with substrates or inhibitors are heterogeneous and consist of several well defined subspecies. The data show that NO, and presumably also O2, has access to the active site Fe2+ in the enzyme-substrate complex. The use of EPR-detectable NO complexes as a rapid and sensitive tool for the study of the EPR silent active site iron of extradiol dioxygenases is discussed.
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62
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Arciero DM, Lipscomb JD, Huynh BH, Kent TA, Münck E. EPR and Mössbauer studies of protocatechuate 4,5-dioxygenase. Characterization of a new Fe2+ environment. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(17)43760-4] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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63
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Hille R, Yoshida T, Tarr GE, Williams CH, Ludwig ML, Fee JA, Kent TA, Huynh BH, Münck E. Studies of the ferredoxin from Thermus thermophilus. J Biol Chem 1983; 258:13008-13. [PMID: 6313685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The soluble ferredoxin from Thermus thermophilus was examined by Mössbauer and EPR spectroscopies and by reductive titrations. These studies demonstrate the presence of one 3Fe center, responsible for the characteristic g = 2.02 EPR signal in the oxidized protein, and one [4Fe-4S] center which is responsible for the rhombic EPR spectrum of the fully reduced protein. These assignments should replace those made by Ohnishi et al. (Ohnishi, T., Blum, H., Sato, S., Nakazawa, K., Hon-nami, K., and Oshima, T. (1980) J. Biol. Chem. 255, 345-348) prior to the discovery of the 3Fe clusters. The amino acid composition was determined and is discussed with reference to recent structural studies of 7Fe ferredoxins.
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64
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Hille R, Yoshida T, Tarr GE, Williams CH, Ludwig ML, Fee JA, Kent TA, Huynh BH, Münck E. Studies of the ferredoxin from Thermus thermophilus. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(17)44072-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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65
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Teixeira M, Moura I, Xavier AV, Dervartanian DV, Legall J, Peck HD, Huynh BH, Moura JJ. Desulfovibrio Gigas hydrogenase: redox properties of the nickel and iron-sulfur centers. EUROPEAN JOURNAL OF BIOCHEMISTRY 1983; 130:481-4. [PMID: 6297907 DOI: 10.1111/j.1432-1033.1983.tb07175.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Below 30 K, oxidized Desulfovibrio gigas hydrogenase presents an intense electron paramagnetic resonance (EPR) signal centered at g = 2.02, typical of an iron-sulfur center. In addition a rhombic EPR signal, attributed to Ni(III) species, is also observed [LeGall, J., Ljungdahl, P., Moura, I., Peck, H.D., Jr, Xavier, A.V., Moura, J.J.G., Teixeira, M., Huynh, B.H., and DerVartanian, D.V. (1982) Biochem. Biophys. Res. Commun. 106, 610-616; and Cammack, R., Patil, D., Aguirre, R., and Hatchikian, E.C., (1982) FEBS Lett. 142, 289-292]. At higher temperatures (77 K) the iron-sulfur EPR signal is broader and all the EPR features of the rhombic nickel signal can easily be observed. We have now obtained additional information concerning the redox properties of these EPR active centers, using an EPR redox titration method in the presence of dye mediators at pH = 8.5. The mid-point potential was determined to be -70 mV for the Fe,S cluster and -220 mV for the Ni center. Intermediate oxidation states were obtained upon partial reduction with either dithionite or hydrogen. Although upon dithionite reduction the centers are reduced in the order of decreasing mid-point reduction potentials, under a hydrogen atmosphere the nickel center reduces preferentially. This suggests a catalytic involvement of the nickel redox center in the binding of hydrogen. Preliminary Mössbauer studies on Desulfovibrio gigas hydrogenase reveal the presence of a paramagnetic 3 Fe center and two 4 Fe centers. The 3 Fe center is responsible for the g = 2.02 EPR signal but the two 4 Fe centers have been so far undetectable by EPR.
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Krüger HJ, Huynh BH, Ljungdahl PO, Xavier AV, Der Vartanian DV, Moura I, Peck HD, Teixeira M, Moura JJ, LeGall J. Evidence for nickel and a three-iron center in the hydrogenase of Desulfovibrio desulfuricans. J Biol Chem 1982; 257:14620-3. [PMID: 6294073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Hydrogenase from Desulfovibrio desulfuricans (ATCC No. 27774) grown in unenriched and in enriched 61Ni and 57Fe media has been purified to apparent homogeneity. Two fractions of enzymes with hydrogenase activity were separated and were termed hydrogenase I and hydrogenase II. they were shown to have similar molecular weights (77,600 for hydrogenase I and 75,500 for hydrogenase II), to be composed of two polypeptide chains, and to contain Ni and non-heme iron. Because of its higher specific activity (152 versus 97) hydrogenase II was selected for EPR and Mössbauer studies. As isolated, hydrogenase II exhibits an "isotropic" EPR signal at g = 2.02 and a rhombic EPR signal at g = 2.3, 2.2, and 2.0. Isotopic substitution of 61Ni proves that the rhombic signal is due to Ni. Combining the Mössbauer and EPR data, the isotropic g = 2.02 EPR signal was shown to originate from a 3Fe cluster which may have oxygenous or nitrogenous ligands. In addition, the Mössbauer data also revealed two [4Fe-4S]2+ clusters iun each molecule of hydrogenase II. The EPR and Mössbauer data of hydrogenase I were found to be identical to those of hydrogenase II, indicating that both enzymes have common metallic centers.
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Krüger HJ, Huynh BH, Ljungdahl PO, Xavier AV, Der Vartanian DV, Moura I, Peck HD, Teixeira M, Moura JJ, LeGall J. Evidence for nickel and a three-iron center in the hydrogenase of Desulfovibrio desulfuricans. J Biol Chem 1982. [DOI: 10.1016/s0021-9258(18)33323-4] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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68
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Moura JJ, Moura I, Huynh BH, Krüger HJ, Teixeira M, DuVarney RC, DerVartanian DV, Xavier AV, Peck HD, LeGall J. Unambiguous identification of the nickel EPR signal in 61Ni-enriched Desulfovibrio gigas hydrogenase. Biochem Biophys Res Commun 1982; 108:1388-93. [PMID: 6295382 DOI: 10.1016/s0006-291x(82)80060-0] [Citation(s) in RCA: 69] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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69
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Huynh BH, Lui MC, Moura JJ, Moura I, Ljungdahl PO, Münck E, Payne WJ, Peck HD, DerVartanian DV, LeGall J. Mössbauer and EPR studies on nitrite reductase from Thiobacillus denitrificans. J Biol Chem 1982; 257:9576-81. [PMID: 6286626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
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70
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Moura I, Moura JJ, Huynh BH, Santos H, LeGall J, Xavier AV. Ferredoxin from Methanosarcina barkeri: evidence for the presence of a three-iron center. EUROPEAN JOURNAL OF BIOCHEMISTRY 1982; 126:95-8. [PMID: 6290216 DOI: 10.1111/j.1432-1033.1982.tb06751.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Methanosarcina barkeri ferredoxin was purified and characterized by electron paramagnetic resonance (EPR) and Mössbauer spectroscopy. The purification procedure included chromatographic steps on DEAE-cellulose and gel filtration. The isolated protein is unstable under aerobic conditions. The ferredoxin exhibits charge transfer bands at 283 nm and 405 nm with an absorption ratio A405/A283 = 0.73. Its molecular weight has been estimated to be 20000-22000 by gel filtration chromatography. The native ferredoxin exhibits an intense EPR signal at g = 2.02 and only a very weak g = 1.94 signal develops upon reduction with dithionite. The Mössbauer spectra of the reduced protein are characteristic of a [3Fe-3S] center. The combined EPR and Mössbauer studies show that M. barkeri ferredoxin contains only [3Fe-3S] clusters, similar to Azotobacter vinelandii Fd[Emptage, M.H., Kent, T.A., Huynh, B.H., Rawlings, J., Orme-Johnson, W.H. & Münck, M. (1980) J. Biol. Chem. 255, 1793-1796], Desulfovibrio gigas FdII [Huynh, B.H., Moura, J.J.G., Moura, I., Kent, T.A., LeGall, J., Xavier, A.V. & Münck, E. (1980) J. Biol. Chem. 255, 3242-3244] and mitochondrial beef heart aconitase [Kent, T.A., Dreyer, J.-L., Kennedy, M.C., Huynh, B.H., Emptage, M.H., Beinert, H. & Münck, E. (1982) Proc. Natl Acad. Sci. USA, 79, 1096-1100].
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Moura JJ, Moura I, Kent TA, Lipscomb JD, Huynh BH, LeGall J, Xavier AV, Münck E. Interconversions of [3Fe-3S] and [4Fe-4S] clusters. Mössbauer and electron paramagnetic resonance studies of Desulfovibrio gigas ferredoxin II. J Biol Chem 1982; 257:6259-67. [PMID: 6281263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
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72
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Moura JJ, Moura I, Kent TA, Lipscomb JD, Huynh BH, LeGall J, Xavier AV, Münck E. Interconversions of [3Fe-3S] and [4Fe-4S] clusters. Mössbauer and electron paramagnetic resonance studies of Desulfovibrio gigas ferredoxin II. J Biol Chem 1982. [DOI: 10.1016/s0021-9258(20)65132-8] [Citation(s) in RCA: 77] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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73
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LeGall J, Ljungdahl PO, Moura I, Peck HD, Xavier AV, Moura JJ, Teixera M, Huynh BH, DerVartanian DV. The presence of redox-sensitive nickel in the periplasmic hydrogenase from Desulfovibrio gigas. Biochem Biophys Res Commun 1982; 106:610-6. [PMID: 6285924 DOI: 10.1016/0006-291x(82)91154-8] [Citation(s) in RCA: 126] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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74
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Kent TA, Dreyer JL, Kennedy MC, Huynh BH, Emptage MH, Beinert H, Münck E. Mössbauer studies of beef heart aconitase: evidence for facile interconversions of iron-sulfur clusters. Proc Natl Acad Sci U S A 1982; 79:1096-100. [PMID: 6280166 PMCID: PMC345907 DOI: 10.1073/pnas.79.4.1096] [Citation(s) in RCA: 138] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Beef heart aconitase, isolated under aerobic conditions, has been studied with Mössbauer and EPR spectroscopy. In the oxidized state, the enzyme exhibits an EPR signal at g = 2.01. The Mössbauer data show that this signal is associated with a 3Fe cluster. In dithionite-reduced aconitase, the 3Fe cluster, probably of the [3Fe-3S] type, is in a paramagnetic state of interger electronic spin (S = 2); the Mössbauer spectra exhibit al the unique features reported for proteins with 3Fe clusters. On activation of aconitase with ferrous ion, the paramagnetic 3Fe cluster of dithionite-reduced enzyme is converted into a diamagnetic (S = 0) form. Activation studies with iron enriched in either 27 Fe or 56 Fe suggest that activation transforms the 3Fe cluster into a center that has a [4Fe-4S] core. This conclusion is supported by the observation that EPR signals characteristic of reduced [4Fe-4S] clusters can be elicited under appropriate conditions. It has frequently been assumed that the activation of aconitase with Fe2+ produces an active site containing a single ferrous ion. The data reported here suggest that a ferrous ion is used to rebuild a [4Fe-4S] cluster.
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Kent TA, Huynh BH, Münck E. Iron-sulfur proteins: spin-coupling model for three-iron clusters. Proc Natl Acad Sci U S A 1980; 77:6574-6. [PMID: 6256746 PMCID: PMC350328 DOI: 10.1073/pnas.77.11.6574] [Citation(s) in RCA: 108] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Recent Mössbauer and EPR studies of two ferredoxins and of aconitase have given evidence for a three-iron cluster, probably of a [3Fe-3S] type. The studies of the oxidized EPR-active centers have shown that the three iron sites are characterized by significantly different magnetic hyperfine coupling constants. For the ferredoxin from Azotobacter vinelandii, for instance, we have observed A1 = -41 MHz, A2 = +18 MHz, and [A3] = 5 MHz. We demonstrate here that the magnetic properties of the clusters can be explained with a simple model of three high-spin ferric ions (S = 5/2) exchange-coupled to a system spin S = 1/2. The model assumes isotropic exchange and different couplings between the iron sites. The results show that the three sites have intrinsic hyperfine interactions similar to those of ferric rubredoxin; the differences in the observed interactions reflect the geometrical features of spin coupling. Furthermore, the three exchange coupling constants are equal within a factor of 2. This implies that the three-iron cluster is a single covalently linked structure and should not be considered as a [2Fe-2S] cluster weakly coupled to a third iron atom.
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