title: Tim23, a protein import component of the mitochondrial inner membrane, is required for normal activity of the multiple conductance channel, MCC.
abstract: We previously showed that the conductance of a mitochondrial inner membrane channel, called MCC, was specifically blocked by peptides corresponding to mitochondrial import signals. To determine if MCC plays a role in protein import, we examined the relationship between MCC and Tim23p, a component of the protein import complex of the mitochondrial inner membrane. We find that antibodies against Tim23p, previously shown to inhibit mitochondrial protein import, inhibit MCC activity. We also find that MCC activity is altered in mitochondria isolated from yeast carrying the tim23-1 mutation. In contrast to wild-type MCC, we find that the conductance of MCC from the tim23-1 mutant is not significantly blocked by mitochondrial presequence peptides. Tim23 antibodies and the tim23-1 mutation do not, however, alter the activity of PSC, a presequence-peptide sensitive channel in the mitochondrial outer membrane. Our results show that Tim23p is required for normal MCC activity and raise the possibility that precursors are translocated across the inner membrane through the pore of MCC.
authors.affiliation: Department of Biological Sciences, University at Albany, SUNY, New York 12222, USA.
authors.forename: T A
authors.initials: TA
authors.lastname: Lohret
authors.forename: R E
authors.initials: RE
authors.lastname: Jensen
authors.forename: K W
authors.initials: KW
authors.lastname: Kinnally
mesh_terms: D000595:Amino Acid Sequence; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D003576:Electron Transport Complex IV; D007425:Intracellular Membranes / Q000737:chemistry; D007473:Ion Channels / Q000378:metabolism; D008565:Membrane Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D026901:Membrane Transport Proteins; D008928:Mitochondria / Q000378:metabolism*; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D018408:Patch-Clamp Techniques; D018272:Porins; D021382:Protein Sorting Signals / Q000138:chemical synthesis / Q000494:pharmacology; D011510:Proteolipids / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D050994:Voltage-Dependent Anion Channels
chemical_list: D002352:Carrier Proteins; D007473:Ion Channels; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D018272:Porins; D021382:Protein Sorting Signals; D011510:Proteolipids; D029701:Saccharomyces cerevisiae Proteins; C083081:TIM23 protein, S cerevisiae; D050994:Voltage-Dependent Anion Channels; C093986:peptide sensitive channel; C020485:proteoliposomes; D003576:Electron Transport Complex IV