title: Characterization of the bifunctional cytochrome c reductase-processing peptidase complex from potato mitochondria.
abstract: In potato, cytochrome c reductase, a protein complex of the respiratory chain, exhibits processing activity toward mitochondrial precursor proteins. One of the two cooperating components of the processing peptidase was shown to be identical with subunit III of the complex. Here we report that two additional proteins of the complex (subunit I and II) share 40-50% sequence identity with the processing enhancing protein, the other component of the processing enzyme from fungi and mammals. Thus the composition and structure of the complex integrated processing peptidase seems to be different from its fungal and mammalian counterparts. Cytochrome c reductase from potato is extraordinarily stable, and separation of subunit III from the complex leads to aggregation of the remaining subcomplex and irreversible loss of processing activity. Expression of the three high molecular weight subunits of the complex allowed purification of each individual protein. Neither the individual subunits nor their combinations are active in in vitro processing assays suggesting that they may need the structural support of the complex for activity. In contrast to mitochondrial processing peptidases from other organisms, the purified potato enzyme is active in the presence of high salt (above 1 M NaCl) and works efficiently without addition of metal ions. These data indicate that potato cytochrome c reductase is a bifunctional protein complex with unique features. Possibly, there is a more general evolutionary relationship between cytochrome c reductases and mitochondrial processing peptidases than hitherto assumed.
authors.affiliation: Institut für Genbiologische Forschung Berlin GmbH, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Emmermann
authors.forename: H P
authors.initials: HP
authors.lastname: Braun
authors.forename: M
authors.initials: M
authors.lastname: Arretz
authors.forename: U K
authors.initials: UK
authors.lastname: Schmitz
mesh_terms: D000595:Amino Acid Sequence; D001965:Bromides / Q000494:pharmacology; D004247:DNA / Q000737:chemistry / Q000302:isolation & purification; D010450:Endopeptidases / Q000378:metabolism*; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D046911:Macromolecular Substances; D008928:Mitochondria / Q000201:enzymology*; D008970:Molecular Weight; D009245:NADH Dehydrogenase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017830:Octoxynol; D011092:Polyethylene Glycols / Q000494:pharmacology; D011498:Protein Precursors / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D017385:Sequence Homology; D012964:Sodium / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology; D017670:Sodium Compounds; D012974:Sodium Iodide / Q000494:pharmacology; D011198:Solanum tuberosum / Q000201:enzymology* / Q000648:ultrastructure
chemical_list: D001965:Bromides; D046911:Macromolecular Substances; D011498:Protein Precursors; D011994:Recombinant Proteins; D017670:Sodium Compounds; D011092:Polyethylene Glycols; D012965:Sodium Chloride; D017830:Octoxynol; D004247:DNA; D012964:Sodium; D009245:NADH Dehydrogenase; D010450:Endopeptidases; D012974:Sodium Iodide; C027938:sodium bromide