title: Effect of leader peptides on the permeability of mitochondria.
abstract: Peptides with sequences based on the leader sequence of yeast cytochrome c oxidase subunit IV (pCOX IV-(1-25)) activate the electrophoretic uptake of K+ and other cations such as tetraethylammonium and lysine by rat liver mitochondria with EC50 = 11-15 microM. Uptake of these cations is dependent on respiration and is prevented by uncoupling agents, and the Vmax for K+ is 1.2-1.5 micromol/min/mg. Albeit more slowly, the non-electrolytes mannitol and sucrose are also transported by this pathway. Treatment of the peptides with proteinase K eliminates the stimulatory effect. Since the stimulated rate is not inhibited by ATP or by cyclosporin, we conclude that this pathway is not related to the mitochondrial KATP channel or the Ca2+-dependent permeability transition pore. Transport is stimulated by pCOX IV-(1-23), pCOX IV-(1-22), and pCOX IV-(1-12)Y, but not by a 13-amino acid peptide representing the nuclear location sequence of the SV40 large T antigen, which is responsible for directing that protein to the nucleus. Spermine, which has four positive charges, also has no stimulatory effect, and an amphiphilic 22-residue peptide derived from antithrombin III with seven net charges is only one-twentieth as effective as pCOX IV-(1-22). Thus, these data indicate that the sequence/structure is important for activation of transport. We also demonstrate that mitochondrial uncoupling, previously reported to be induced by these peptides, actually reflects coupled accumulation of salt. In view of our findings, it is also likely that the lytic effects attributed to these peptides are secondary to swelling and are not due to membrane damage per se. Finally, we show that, in non-ionic media, the peptide is an inhibitor of cytochrome c oxidase.
authors.affiliation: Department of Pharmacology, Medical College of Ohio, Toledo, Ohio 43699-0008, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Lu
authors.forename: A D
authors.initials: AD
authors.lastname: Beavis
mesh_terms: D018528:ATP-Binding Cassette Transporters; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001692:Biological Transport / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D003576:Electron Transport Complex IV / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D019286:Endopeptidase K / Q000378:metabolism; D004792:Enzyme Precursors / Q000008:administration & dosage / Q000494:pharmacology*; D007202:Indicators and Reagents / Q000493:pharmacokinetics; D054086:KATP Channels; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D008933:Mitochondrial Swelling / Q000187:drug effects; D008969:Molecular Sequence Data; D010539:Permeability / Q000187:drug effects; D011188:Potassium / Q000493:pharmacokinetics; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying; D021382:Protein Sorting Signals / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D013772:Tetramethylphenylenediamine / Q000493:pharmacokinetics
chemical_list: D018528:ATP-Binding Cassette Transporters; D004792:Enzyme Precursors; D007202:Indicators and Reagents; D054086:KATP Channels; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D021382:Protein Sorting Signals; C092520:uK-ATP-1 potassium channel; D000255:Adenosine Triphosphate; D003576:Electron Transport Complex IV; D019286:Endopeptidase K; D013772:Tetramethylphenylenediamine; D011188:Potassium