The isolated complex of the translocase of the outer membrane of mitochondria. Characterization of the cation-selective and voltage-gated preprotein-conducting pore

• Published in: The Journal of biological chemistry Vol. 273; no. 47; pp. 31032 - 31039
• Main Authors: Kunkele, K.P. (Universitat Munchen, Munich, FRG.), Juin, P, Pompa, C, Nargana, F.E, Nargang, F.E, Henry, J.P, Neupert, W, Lill, R, Thieffry, M
• Format: Journal Article
• Language: English
• Published: United States 20.11.1998
• Subjects: Biological Transport; Carrier Proteins - isolation & purification; Carrier Proteins - metabolism; Cations - metabolism; CELL MEMBRANES; Cell Polarity; CONDUCTIVIDAD ELECTRICA; CONDUCTIVITE ELECTRIQUE; Electric Conductivity; ELECTRIC CURRENT; ELECTRICAL CONDUCTIVITY; ELECTRICIDAD; ELECTRICITE; ELECTRICITY; ELECTROPHYSIOLOGY; ION; Ion Channel Gating; Ion Channels - isolation & purification; Ion Channels - metabolism; ION TRANSPORT; IONES; IONS; Lipid Bilayers; MEMBRANAS CELULARES; MEMBRANE CELLULAIRE; Membrane Proteins - immunology; Membrane Proteins - metabolism; Membrane Transport Proteins; METABOLISME DES PROTEINES; METABOLISMO PROTEICO; MITOCHONDRIA; Mitochondria - metabolism; Mitochondrial Membrane Transport Proteins; MITOCHONDRIE; MITOCONDRIA; NEUROSPORA CRASSA; Neurospora crassa - metabolism; PEPTIDE; PEPTIDES; PEPTIDOS; POTASIO; POTASSIUM; PRECURSORS; PROTEIN METABOLISM; Protein Precursors - metabolism; Protein Sorting Signals - metabolism; PROTEIN TRANSPORT; PROTEINAS; PROTEINE; PROTEINS; Saccharomyces cerevisiae Proteins; SIGNAL PEPTIDE; Subcellular Fractions - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.273.47.31032

The complex of the translocase mitochondrial outer membrane (TOM), mediates recognition, unfolding, and translocation of preproteins. We have used a combination of biochemical and electrophysiological methods to study the properties of the preprotein-conducting pore of the purified TOM complex. The pore is cation-selective and voltage-gated. It shows three main conductance levels with characteristic slow and fast kinetics transitions to states of lower conductance following application of transmembrane voltages. These electrical properties distinguish it from the mitochondrial voltage-dependent anion channel (porin) and are identical to those of the previously described peptide-sensitive channel. Binding of antibodies to the C terminus of Tom40 on the intermembrane space side of the outer membrane modifies the channel properties and allows determination of the orientation of the channel within the lipid bilayer. Mitochondrial presequence peptides specifically interact with the pore and decrease the ion flow through the channel in a voltage-dependent manner. We propose that the presequence-induced closures of the pore are related to structural alterations of the TOM complex observed during the various stages of preprotein movement across the mitochondrial outer membrane.