Direct spectroscopic evidence for the presence of a 6Fe cluster in an iron-sulfur protein isolated from Desulfovibrio desulfuricans (ATCC 27774)

I. Moura, P. Tavares, José J. G. Moura, N. Ravi, Hanh Huynh Boi Hanh Huynh, M. Y. Liu, J. LeGall

Research output: Contribution to journalArticle

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Abstract

A novel iron-sulfur protein was purified from the extract of Desulfovibrio desulfuricans (ATCC 27774) to homogeneity as judged by polyacrylamide gel electrophoresis. The purified protein is a monomer of 57 kDa molecular mass. It contains comparable amounts of iron and inorganic labile sulfur atoms and exhibits an optical spectrum typical of iron-sulfur proteins with maxima at 400, 305, and 280 nm. Mossbauer data of the as-isolated protein show two spectral components, a paramagnetic and a diamagnetic, of equal intensity. Detailed analysis of the paramagnetic component reveals six distinct antiferromagnetically coupled iron sites, providing direct spectroscopic evidence for the presence of a 6Fe cluster in this newly purified protein. One of the iron sites exhibits parameters (ΔE(Q) = 2.67 ± 0.03 mm/s and δ = 1.09 ± 0.02 mm/s at 140 K) typical for high spin ferrous ion; the observed large isomer shift indicates an iron environment that is distinct from the tetrahedral sulfur coordination commonly observed for the iron atoms in iron- sulfur clusters and is consistent with a penta- or hexacoordination containing N and/or O ligands. The other five iron sites are most probably high spin ferric. Three of them show parameters characteristic for tetrahedral sulfur coordination. In correlation with the EPR spectrum of the as-purified protein which shows a resonance signal at g = 15.3 and a group of signals between g = 9.8 and 5.4, this 6Fe cluster is assigned to an unusual spin state of 9/2 with zero field splitting parameters D = -1.3 cm-1 and E/D = 0.062. Other EPR signals attributable to minor impurities are also observed at the g = 4.3 and 2.0 regions. The diamagnetic Mossbauer component represents a second iron cluster, which, upon reduction with dithionite, displays an intense S = 1/2 EPR signal with g values at 2.00, 1.83, and 1.31. In addition, an EPR signal of the S = 3/2 type is also observed for the dithionite-reduced protein.

Original languageEnglish
Pages (from-to)4489-4496
Number of pages8
JournalJournal of Biological Chemistry
Volume267
Issue number7
Publication statusPublished - 1 Jan 1992

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Desulfovibrio desulfuricans
Iron-Sulfur Proteins
Iron
Sulfur
Paramagnetic resonance
Dithionite
Proteins
Atoms
Rubiaceae
Molecular mass
Electrophoresis
Isomers
Polyacrylamide Gel Electrophoresis
Monomers
Impurities
Ions
Ligands

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@article{c8fa8a577b0a4160b9bac343c477e522,
title = "Direct spectroscopic evidence for the presence of a 6Fe cluster in an iron-sulfur protein isolated from Desulfovibrio desulfuricans (ATCC 27774)",
abstract = "A novel iron-sulfur protein was purified from the extract of Desulfovibrio desulfuricans (ATCC 27774) to homogeneity as judged by polyacrylamide gel electrophoresis. The purified protein is a monomer of 57 kDa molecular mass. It contains comparable amounts of iron and inorganic labile sulfur atoms and exhibits an optical spectrum typical of iron-sulfur proteins with maxima at 400, 305, and 280 nm. Mossbauer data of the as-isolated protein show two spectral components, a paramagnetic and a diamagnetic, of equal intensity. Detailed analysis of the paramagnetic component reveals six distinct antiferromagnetically coupled iron sites, providing direct spectroscopic evidence for the presence of a 6Fe cluster in this newly purified protein. One of the iron sites exhibits parameters (ΔE(Q) = 2.67 ± 0.03 mm/s and δ = 1.09 ± 0.02 mm/s at 140 K) typical for high spin ferrous ion; the observed large isomer shift indicates an iron environment that is distinct from the tetrahedral sulfur coordination commonly observed for the iron atoms in iron- sulfur clusters and is consistent with a penta- or hexacoordination containing N and/or O ligands. The other five iron sites are most probably high spin ferric. Three of them show parameters characteristic for tetrahedral sulfur coordination. In correlation with the EPR spectrum of the as-purified protein which shows a resonance signal at g = 15.3 and a group of signals between g = 9.8 and 5.4, this 6Fe cluster is assigned to an unusual spin state of 9/2 with zero field splitting parameters D = -1.3 cm-1 and E/D = 0.062. Other EPR signals attributable to minor impurities are also observed at the g = 4.3 and 2.0 regions. The diamagnetic Mossbauer component represents a second iron cluster, which, upon reduction with dithionite, displays an intense S = 1/2 EPR signal with g values at 2.00, 1.83, and 1.31. In addition, an EPR signal of the S = 3/2 type is also observed for the dithionite-reduced protein.",
author = "I. Moura and P. Tavares and Moura, {Jos{\'e} J. G.} and N. Ravi and {Boi Hanh Huynh}, {Hanh Huynh} and Liu, {M. Y.} and J. LeGall",
note = "NIGMS NIH HHS (GM 41482; GM 32187)",
year = "1992",
month = "1",
day = "1",
language = "English",
volume = "267",
pages = "4489--4496",
journal = "Journal of Biological Chemistry",
issn = "0021-9258",
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Direct spectroscopic evidence for the presence of a 6Fe cluster in an iron-sulfur protein isolated from Desulfovibrio desulfuricans (ATCC 27774). / Moura, I.; Tavares, P.; Moura, José J. G.; Ravi, N.; Boi Hanh Huynh, Hanh Huynh; Liu, M. Y.; LeGall, J.

In: Journal of Biological Chemistry, Vol. 267, No. 7, 01.01.1992, p. 4489-4496.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Direct spectroscopic evidence for the presence of a 6Fe cluster in an iron-sulfur protein isolated from Desulfovibrio desulfuricans (ATCC 27774)

AU - Moura, I.

AU - Tavares, P.

AU - Moura, José J. G.

AU - Ravi, N.

AU - Boi Hanh Huynh, Hanh Huynh

AU - Liu, M. Y.

AU - LeGall, J.

N1 - NIGMS NIH HHS (GM 41482; GM 32187)

PY - 1992/1/1

Y1 - 1992/1/1

N2 - A novel iron-sulfur protein was purified from the extract of Desulfovibrio desulfuricans (ATCC 27774) to homogeneity as judged by polyacrylamide gel electrophoresis. The purified protein is a monomer of 57 kDa molecular mass. It contains comparable amounts of iron and inorganic labile sulfur atoms and exhibits an optical spectrum typical of iron-sulfur proteins with maxima at 400, 305, and 280 nm. Mossbauer data of the as-isolated protein show two spectral components, a paramagnetic and a diamagnetic, of equal intensity. Detailed analysis of the paramagnetic component reveals six distinct antiferromagnetically coupled iron sites, providing direct spectroscopic evidence for the presence of a 6Fe cluster in this newly purified protein. One of the iron sites exhibits parameters (ΔE(Q) = 2.67 ± 0.03 mm/s and δ = 1.09 ± 0.02 mm/s at 140 K) typical for high spin ferrous ion; the observed large isomer shift indicates an iron environment that is distinct from the tetrahedral sulfur coordination commonly observed for the iron atoms in iron- sulfur clusters and is consistent with a penta- or hexacoordination containing N and/or O ligands. The other five iron sites are most probably high spin ferric. Three of them show parameters characteristic for tetrahedral sulfur coordination. In correlation with the EPR spectrum of the as-purified protein which shows a resonance signal at g = 15.3 and a group of signals between g = 9.8 and 5.4, this 6Fe cluster is assigned to an unusual spin state of 9/2 with zero field splitting parameters D = -1.3 cm-1 and E/D = 0.062. Other EPR signals attributable to minor impurities are also observed at the g = 4.3 and 2.0 regions. The diamagnetic Mossbauer component represents a second iron cluster, which, upon reduction with dithionite, displays an intense S = 1/2 EPR signal with g values at 2.00, 1.83, and 1.31. In addition, an EPR signal of the S = 3/2 type is also observed for the dithionite-reduced protein.

AB - A novel iron-sulfur protein was purified from the extract of Desulfovibrio desulfuricans (ATCC 27774) to homogeneity as judged by polyacrylamide gel electrophoresis. The purified protein is a monomer of 57 kDa molecular mass. It contains comparable amounts of iron and inorganic labile sulfur atoms and exhibits an optical spectrum typical of iron-sulfur proteins with maxima at 400, 305, and 280 nm. Mossbauer data of the as-isolated protein show two spectral components, a paramagnetic and a diamagnetic, of equal intensity. Detailed analysis of the paramagnetic component reveals six distinct antiferromagnetically coupled iron sites, providing direct spectroscopic evidence for the presence of a 6Fe cluster in this newly purified protein. One of the iron sites exhibits parameters (ΔE(Q) = 2.67 ± 0.03 mm/s and δ = 1.09 ± 0.02 mm/s at 140 K) typical for high spin ferrous ion; the observed large isomer shift indicates an iron environment that is distinct from the tetrahedral sulfur coordination commonly observed for the iron atoms in iron- sulfur clusters and is consistent with a penta- or hexacoordination containing N and/or O ligands. The other five iron sites are most probably high spin ferric. Three of them show parameters characteristic for tetrahedral sulfur coordination. In correlation with the EPR spectrum of the as-purified protein which shows a resonance signal at g = 15.3 and a group of signals between g = 9.8 and 5.4, this 6Fe cluster is assigned to an unusual spin state of 9/2 with zero field splitting parameters D = -1.3 cm-1 and E/D = 0.062. Other EPR signals attributable to minor impurities are also observed at the g = 4.3 and 2.0 regions. The diamagnetic Mossbauer component represents a second iron cluster, which, upon reduction with dithionite, displays an intense S = 1/2 EPR signal with g values at 2.00, 1.83, and 1.31. In addition, an EPR signal of the S = 3/2 type is also observed for the dithionite-reduced protein.

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M3 - Article

VL - 267

SP - 4489

EP - 4496

JO - Journal of Biological Chemistry

JF - Journal of Biological Chemistry

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