Electrochemical and spectroscopic properties of the iron-sulfur flavoprotein from Methanosarcina thermophila

Donald F Becker, Ubolsree Leartsakulpanich, Kristene K. Surerus, James G. Ferry, Stephen W. Ragsdale

Research output: Contribution to journalArticle

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Abstract

An iron-sulfur flavoprotein (Isf) from the methanoarchaeaon Methanosarcina thermophila, which participates in electron transfer reactions required for the fermentation of acetate to methane, was characterized by electrochemistry and EPR and Mossbauer spectroscopy. The midpoint potential (E(m)) of the FMN/FMNH2 couple was -0.277 V. No flavin semiquinone was observed during potentiometric titrations; however, low amounts of the radical were observed when Isf was quickly frozen after reaction with CO and the CO dehydrogenase/acetyl-CoA synthase complex from M. thermophila. Isf contained a [4Fe-4S](2+/1+) cluster with g values of 2.06 and 1.93 and an unusual split signal with g values at 1.86 and 1.82. The unusual morphology was attributed to microheterogeneity among Isf molecules. The E(m) value for the 2+/1+ redox couple of the cluster was -0.394 V. Extracts from H2-CO2- grown Methanobacterium thermoautotrophicum cells catalyzed either the H2- or CO-dependent reduction of M. thermophila Isf. In addition, Isf homologs were found in the genomic sequences of the CO2-reducing methanoarchaea M. thermoautotrophicum and Methanococcus jannaschii. These results support a general role for Isf in electron transfer reactions of both acetate- fermenting and CO2-reducing methanoarchaea. It is suggested that Isf functions to couple electron transfer from ferredoxin to membrane-bound electron carriers, such as methanophenazine and/or b-type cytochromes.

Original languageEnglish (US)
Pages (from-to)26462-26469
Number of pages8
JournalJournal of Biological Chemistry
Volume273
Issue number41
DOIs
StatePublished - Oct 9 1998

Fingerprint

Flavoproteins
Sulfur
Iron
Electrons
carbon monoxide dehydrogenase
Carbon Monoxide
Acetates
Electron-Transferring Flavoproteins
Cytochrome b Group
Methanocaldococcus
Methanobacterium
Mossbauer Spectroscopy
Electrochemistry
Flavin Mononucleotide
Ferredoxins
Acetyl Coenzyme A
Methane
Mossbauer spectroscopy
Methanosarcina thermophila Isf protein
Titration

ASJC Scopus subject areas

  • Biochemistry

Cite this

Electrochemical and spectroscopic properties of the iron-sulfur flavoprotein from Methanosarcina thermophila. / Becker, Donald F; Leartsakulpanich, Ubolsree; Surerus, Kristene K.; Ferry, James G.; Ragsdale, Stephen W.

In: Journal of Biological Chemistry, Vol. 273, No. 41, 09.10.1998, p. 26462-26469.

Research output: Contribution to journalArticle

Becker, Donald F ; Leartsakulpanich, Ubolsree ; Surerus, Kristene K. ; Ferry, James G. ; Ragsdale, Stephen W. / Electrochemical and spectroscopic properties of the iron-sulfur flavoprotein from Methanosarcina thermophila. In: Journal of Biological Chemistry. 1998 ; Vol. 273, No. 41. pp. 26462-26469.
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