title: Interactions of mitochondrial presequence peptides with the mitochondrial outer membrane preprotein translocase TOM.
abstract: TOM protein-conducting channels serve as the main entry sites into mitochondria for virtually all mitochondrial proteins. When incorporated into lipid bilayers, they form large, relatively nonspecific ion channels that are blocked by peptides derived from mitochondrial precursor proteins. Using single-channel electrical recordings, we analyzed the interactions of mitochondrial presequence peptides with single TOM pores. The largest conductance state of the translocon represents the likely protein-conducting conformation of the channel. The frequency (but not the duration) of the polypeptide-induced blockage is strongly modulated by the substrate concentration. Structural differences between substrates are reflected in characteristic blockage frequencies and duration of blockage. To our knowledge, this study provides first quantitative data regarding the kinetics of polypeptide interaction with the mitochondrial TOM machinery.
authors.affiliation: Biophysics Department, Institute of Biology, University of Stuttgart, Stuttgart, Germany.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Romero-Ruiz
authors.forename: Kozhinjampara R
authors.initials: KR
authors.lastname: Mahendran
authors.forename: Reiner
authors.initials: R
authors.lastname: Eckert
authors.forename: Mathias
authors.initials: M
authors.lastname: Winterhalter
authors.forename: Stephan
authors.initials: S
authors.lastname: Nussberger
mesh_terms: D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000378:metabolism*; D015640:Ion Channel Gating; D007473:Ion Channels / Q000378:metabolism; D007700:Kinetics; D008564:Membrane Potentials / Q000502:physiology; D008928:Mitochondria / Q000201:enzymology* / Q000648:ultrastructure; D051336:Mitochondrial Membranes / Q000201:enzymology* / Q000378:metabolism / Q000648:ultrastructure; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D009492:Neurospora crassa / Q000378:metabolism / Q000648:ultrastructure; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011498:Protein Precursors / Q000378:metabolism*; D021382:Protein Sorting Signals; D013379:Substrate Specificity; D013997:Time Factors
chemical_list: D002352:Carrier Proteins; D007473:Ion Channels; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins; D010455:Peptides; D011498:Protein Precursors; D021382:Protein Sorting Signals