title: Characterization of peptides released from mitochondria: evidence for constant proteolysis and peptide efflux.
abstract: Conserved ATP-dependent proteases ensure the quality control of mitochondrial proteins and control essential steps in mitochondrial biogenesis. Recent studies demonstrated that non-assembled mitochondrially encoded proteins are degraded to peptides and amino acids that are released from mitochondria. Here, we have characterized peptides extruded from mitochondria by mass spectrometry and identified 270 peptides that are exported in an ATP- and temperature-dependent manner. The peptides originate from 51 mitochondrially and nuclearly encoded proteins localized mainly in the matrix and inner membrane, indicating that peptides generated by the activity of all known mitochondrial ATP-dependent proteases can be released from the organelle. Pulse-labeling experiments in logarithmically growing yeast cells revealed that approximately 6-12% of preexisting and newly imported proteins is degraded and contribute to this peptide pool. Under respiring conditions, we observed an increased proteolysis of newly imported proteins that suggests a higher turnover rate of respiratory chain components and thereby rationalizes the predominant appearance of representatives of this functional class in the detected peptide pool. These results demonstrated a constant efflux of peptides from mitochondria and provided new insight into the stability of the mitochondrial proteome and the efficiency of mitochondrial biogenesis.
authors.affiliation: Institut für Genetik and Zentrum für Molekulare Medizin, Universität zu Köln, 50674 Köln, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Augustin
authors.forename: Mark
authors.initials: M
authors.lastname: Nolden
authors.forename: Stefan
authors.initials: S
authors.lastname: Müller
authors.forename: Olaf
authors.initials: O
authors.lastname: Hardt
authors.forename: Isabel
authors.initials: I
authors.lastname: Arnold
authors.forename: Thomas
authors.initials: T
authors.lastname: Langer
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D003576:Electron Transport Complex IV / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D005656:Fungal Proteins / Q000737:chemistry; D013058:Mass Spectrometry; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry*; D021381:Protein Transport; D011506:Proteins / Q000737:chemistry*; D020543:Proteome; D013696:Temperature; D013997:Time Factors
chemical_list: D005656:Fungal Proteins; D024101:Mitochondrial Proteins; D010455:Peptides; D011506:Proteins; D020543:Proteome; D000255:Adenosine Triphosphate; C117108:cytochrome C oxidase subunit II; D003576:Electron Transport Complex IV