title: Basic peptides can be imported into yeast mitochondria by two distinct targeting pathways. Involvement of the peptide-sensitive channel of the outer membrane.
abstract: The interaction of several basic peptides with yeast mitochondria has been analyzed. The peptides were selected for their ability to block a cationic channel of the outer membrane, the peptide-sensitive channel. These peptides possess common characteristics, such as a net positive charge superior to 2 and the capacity to form amphiphilic structures. They can be divided into two classes as follows: peptides of class I derived from mitochondrial signal peptides, such as the presequence of cytochrome c oxidase subunit IV, e.g. pCyt OX IV (1-12) Y; and peptides of class II unrelated to the mitochondria, such as dynorphin B (1-13). Class I peptides inhibited the translocation of a chimeric protein, cytochrome b2-DHFR, into the mitochondrial matrix, whereas peptides of class II failed to inhibit this import. Experiments with iodinated pCyt OX IV (1-12) Y and dynorphin B (1-13) showed, however, that both types of peptides were imported into yeast mitochondria in vitro and subsequently degraded. At 30 degrees C, two import mechanisms could be distinguished; the mitochondrial presequences (class I) were translocated into the matrix in a temperature- and potential-sensitive manner, probably along the general import pathway, while class II dynorphin B (1-13) was imported into the intermembrane space by a process that was neither temperature- nor potential-sensitive. At 0 degree C, both peptides were imported in a class II manner. The class II characteristics suggested the existence of a direct pathway into the intermembrane space, which may be associated with the peptide-sensitive channel. This hypothesis is substantiated by the competition for the import into the mitochondria between peptides of the two classes. The import of pCyt OX (1-12) Y was inhibited at 30 degrees C only by peptides of class I, IV whereas, at 0 degree C, this import was also inhibited by peptides of class II. Import of peptides of the latter class was inhibited by peptides of the two classes both at 0 degree C and 30 degrees C.
authors.affiliation: Centre National de la Recherche Scientifique, Unité de Recherche Associée 1112, Paris, France.
authors.forename: F M
authors.initials: FM
authors.lastname: Vallette
authors.forename: P
authors.initials: P
authors.lastname: Juin
authors.forename: M
authors.initials: M
authors.lastname: Pelleschi
authors.forename: J P
authors.initials: JP
authors.lastname: Henry
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D001692:Biological Transport; D004399:Dynorphins / Q000031:analogs & derivatives / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism; D004723:Endorphins / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000378:metabolism*; D007473:Ion Channels / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000235:genetics / Q000378:metabolism; D042844:L-Lactate Dehydrogenase (Cytochrome); D008564:Membrane Potentials; D008928:Mitochondria / Q000378:metabolism*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D018272:Porins / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D013696:Temperature; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics / Q000378:metabolism; D014357:Trypsin
chemical_list: D004723:Endorphins; D007473:Ion Channels; D010446:Peptide Fragments; D010455:Peptides; D018272:Porins; D011993:Recombinant Fusion Proteins; D004399:Dynorphins; C036200:rimorphin; D007770:L-Lactate Dehydrogenase; D042844:L-Lactate Dehydrogenase (Cytochrome); D013762:Tetrahydrofolate Dehydrogenase; D003576:Electron Transport Complex IV; D014357:Trypsin