title: Isolation and characterization of polyferredoxin from Methanobacterium thermoautotrophicum. The mvhB gene product of the methylviologen-reducing hydrogenase operon.
abstract: The methylviologen-reducing hydrogenase operon of Methanobacterium thermoautotrophicum contains an open reading frame, mvhB, the product of which was predicted to have a molecular weight of 44 kDa and to contain as many as 48 iron atoms in 12 [4Fe-4S] clusters, and was therefore suggested to be a polyferredoxin. We have now, for the first time, isolated this polyferredoxin. Its identity with the mvhB gene product was evidenced by a comparison of the N-terminal amino acid sequence. The dark-brown protein of apparent molecular weight 44 kDa was found to contain 53 mol Fe and 43 mol acid-labile sulfur per mol. The UV/visible spectrum showed two maxima at 280 nm and 390 nm, and a shoulder at 308 nm. The A390/A280 ratio was 0.73. The molar extinction coefficient at 390 nm was 170,000 M-1.cm-1. In the dithionite reduced state the protein displayed an EPR spectrum like that of [4Fe-4S] clusters. The results indicate that the mvhB gene product is indeed a polyferredoxin.
authors.affiliation: Laboratorium für Mikrobiologie, Fachbereich Biologie, Philipps-Universität Marburg, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Hedderich
authors.forename: S P
authors.initials: SP
authors.lastname: Albracht
authors.forename: D
authors.initials: D
authors.lastname: Linder
authors.forename: J
authors.initials: J
authors.lastname: Koch
authors.forename: R K
authors.initials: RK
authors.lastname: Thauer
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D002384:Catalysis; D004578:Electron Spin Resonance Spectroscopy; D005288:Ferredoxins / Q000235:genetics* / Q000302:isolation & purification; D006864:Hydrogenase / Q000737:chemistry / Q000235:genetics*; D007501:Iron / Q000737:chemistry; D017014:Methanobacterium / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009876:Operon; D010084:Oxidation-Reduction; D013053:Spectrophotometry; D014755:Viologens / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D005288:Ferredoxins; D014755:Viologens; D007501:Iron; D006864:Hydrogenase