Characterization of the bifunctional cytochrome c reductase-processing peptidase complex from potato mitochondria
Creators: name: Emmermann, M.
name: Braun, Hans-Peter
name: Arretz, M.
name: Schmitz, U.K.
Publisher: name: Bethesda, Md. : ASBMB Publications
Year: 1993
Subjects: subject: mitochondrial enzyme
subject: peptidase
subject: protein precursor
subject: protein subunit
subject: reduced nicotinamide adenine dinucleotide dehydrogenase
subject: sodium chloride
subject: vegetable protein
subject: article
subject: enzyme activity
subject: mitochondrial energy transfer
subject: molecular weight
subject: potato
subject: priority journal
subject: protein localization
subject: protein processing
subject: protein protein interaction
subject: protein purification
subject: protein quaternary structure
subject: protein stability
subject: sequence homology
subject: Amino Acid Sequence
subject: Bromides
subject: DNA
subject: Endopeptidases
subject: Enzyme Stability
subject: Escherichia coli
subject: Gene Expression
subject: Macromolecular Systems
subject: Mitochondria
subject: Molecular Weight
subject: NADH Dehydrogenase
subject: Octoxynol
subject: Polyethylene Glycols
subject: Potatoes
subject: Protein Precursors
subject: Recombinant Proteins
subject: Sequence Homology
subject: Sodium
subject: Sodium Chloride
subject: Sodium Iodide
subject: Support, Non-U.S. Gov't
subject: Fungi
subject: Mammalia
subject: Solanum tuberosum
subject: Dewey Decimal Classification::500 | Naturwissenschaften::570 | Biowissenschaften, Biologie
subject: Dewey Decimal Classification::500 | Naturwissenschaften::540 | Chemie

description: 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.