title: Soluble cytochromes from the marine methanotroph Methylomonas sp. strain A4.
abstract: Soluble c-type cytochromes are central to metabolism of C1 compounds in methylotrophic bacteria. In order to characterize the role of c-type cytochromes in methane-utilizing bacteria (methanotrophs), we have purified four different cytochromes, cytochromes c-554, c-553, c-552, and c-551, from the marine methanotroph Methylomonas sp. strain A4. The two major species, cytochromes c-554 and c-552, were monoheme cytochromes and accounted for 57 and 26%, respectively, of the soluble c-heme. The approximate molecular masses were 8,500 daltons (Da) (cytochrome c-554) and 14,000 Da (cytochrome c-552), and the isoelectric points were pH 6.4 and 4.7, respectively. Two possible diheme c-type cytochromes were also isolated in lesser amounts from Methylomonas sp. strain A4, cytochromes c-551 and c-553. These were 16,500 and 34,000 Da, respectively, and had isoelectric points at pH 4.75 and 4.8, respectively. Cytochrome c-551 accounted for 9% of the soluble c-heme, and cytochrome c-553 accounted for 8%. All four cytochromes differed in their oxidized versus reduced absorption maxima and their extinction coefficients. In addition, cytochromes c-554, c-552, and c-551 were shown to have different electron paramagnetic spectra and N-terminal amino acid sequences. None of the cytochromes showed significant activity with purified methanol dehydrogenase in vitro, but our data suggested that cytochrome c-552 is probably the in vivo electron acceptor for the methanol dehydrogenase.
authors.affiliation: Keck Laboratories 138-78, California Institute of Technology, Pasadena 91125.
authors.forename: A A
authors.initials: AA
authors.lastname: DiSpirito
authors.forename: J D
authors.initials: JD
authors.lastname: Lipscomb
authors.forename: M E
authors.initials: ME
authors.lastname: Lidstrom
mesh_terms: D000429:Alcohol Oxidoreductases / Q000378:metabolism; D000595:Amino Acid Sequence; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003574:Cytochrome c Group / Q000302:isolation & purification* / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D004591:Electrophoresis, Polyacrylamide Gel; D007525:Isoelectric Focusing; D008772:Methylococcaceae / Q000378:metabolism*; D008969:Molecular Sequence Data; D012623:Seawater; D012995:Solubility; D013053:Spectrophotometry
chemical_list: D003574:Cytochrome c Group; D000429:Alcohol Oxidoreductases; C019641:alcohol dehydrogenase (acceptor)