title: A polyferredoxin with eight [4Fe-4S] clusters as a subunit of molybdenum formylmethanofuran dehydrogenase from Methanosarcina barkeri.
abstract: Formylmethanofuran dehydrogenase (Fmd) from Methanosarcina barkeri is a molybdenum iron-sulfur protein involved in methanogenesis. The enzyme contains approximately 30 mol non-heme iron/mol and 30 mol acid-labile sulfur/mol. We report here the cloning and sequencing of the encoding genes, and that these genes form a transcription unit fmdEFACDB. Evidence is provided that the subunit FmdB harbours the molybdenum-containing active site and may bind one [4Fe-4S] cluster. fmdF encodes a protein with four tandemly repeated bacterial-ferredoxin-like domains and is predicted to be a polyferredoxin that could contain as many as 32 iron atoms in eight [4Fe-4S] clusters. The other genes code for proteins without sequence motifs characteristic for iron-sulfur proteins. These findings suggest that most of the iron-sulfur clusters present in the purified formylmethanofuran dehydrogenase are associated with the subunit FmdF. The finding that FmdF forms a tight complex with the other subunits of formylmethanofuran dehydrogenase indicates a function of the polyferredoxin in the reaction catalyzed by the enzyme. fmdE encodes a protein not present in the purified enzyme. All six genes of the fmd operon were expressed in Escherichia coli and yielded proteins of expected molecular masses. A malE-fmdF gene fusion was constructed and expressed in E. coli, making the apoprotein of the polyferredoxin available in preparative amounts.
authors.affiliation: Max-Planck-Institut für terrestrische Mikrobiologie, Philipps-Universität, Marburg, Germany.
authors.forename: J A
authors.initials: JA
authors.lastname: Vorholt
authors.forename: M
authors.initials: M
authors.lastname: Vaupel
authors.forename: R K
authors.initials: RK
authors.lastname: Thauer
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D000595:Amino Acid Sequence; D019843:Archaeal Proteins; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics; D005288:Ferredoxins / Q000737:chemistry*; D005798:Genes, Bacterial; D008667:Metalloproteins / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D017021:Methanosarcina barkeri / Q000737:chemistry* / Q000235:genetics; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012329:RNA, Bacterial / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D017421:Sequence Analysis; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
chemical_list: D019843:Archaeal Proteins; D001426:Bacterial Proteins; D005288:Ferredoxins; D008667:Metalloproteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D011994:Recombinant Proteins; D000445:Aldehyde Oxidoreductases; C099218:FmdF protein, Methanosarcina barkeri; C060639:formylmethanofuran dehydrogenase