Abstract
Proteins imported into the mitochondrial matrix are synthesized in the cytosol with an N-terminal presequence and are translocated through hetero-oligomeric translocase complexes of the outer and inner mitochondrial membranes. The channel across the inner membrane is formed by the presequence translocase, which consists of roughly six distinct subunits; however, it is not known which subunits actually form the channel. Here we report that purified Tim23 forms a hydrophilic, approximately 13-24 A wide channel characteristic of the mitochondrial presequence translocase. The Tim23 channel is cation selective and activated by a membrane potential and presequences. The channel is formed by the C-terminal domain of Tim23 alone, whereas the N-terminal domain is required for selectivity and a high-affinity presequence interaction. Thus, Tim23 forms a voltage-sensitive high-conductance channel with specificity for mitochondrial presequences.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Carrier Proteins / chemistry
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Carrier Proteins / metabolism
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Electrophysiology
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Intracellular Membranes / chemistry
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Intracellular Membranes / enzymology
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Intracellular Membranes / metabolism
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Ion Channel Gating*
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Lipid Bilayers / chemistry
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Lipid Bilayers / metabolism
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Liposomes / chemistry
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Liposomes / metabolism
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Macromolecular Substances
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Membrane Potentials
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Membrane Proteins / chemistry
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Membrane Proteins / metabolism
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Membrane Transport Proteins / chemistry*
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Membrane Transport Proteins / genetics
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Membrane Transport Proteins / metabolism*
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Mitochondria / chemistry*
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Mitochondria / enzymology
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Mitochondria / genetics
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Mitochondria / metabolism*
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Mitochondrial Membrane Transport Proteins*
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Mitochondrial Precursor Protein Import Complex Proteins
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Mutation / genetics
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Permeability
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Protein Binding
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Protein Precursors / chemistry
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Protein Precursors / metabolism*
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Protein Sorting Signals / physiology*
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Protein Structure, Quaternary
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Protein Structure, Tertiary
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Protein Subunits
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Protein Transport
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Repressor Proteins*
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Saccharomyces cerevisiae / cytology
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Saccharomyces cerevisiae / enzymology
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / metabolism
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Saccharomyces cerevisiae Proteins / chemistry*
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Saccharomyces cerevisiae Proteins / genetics
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Saccharomyces cerevisiae Proteins / metabolism*
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Substrate Specificity
Substances
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Carrier Proteins
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Lipid Bilayers
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Liposomes
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Macromolecular Substances
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Membrane Proteins
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Membrane Transport Proteins
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Mitochondrial Membrane Transport Proteins
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Mitochondrial Precursor Protein Import Complex Proteins
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Protein Precursors
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Protein Sorting Signals
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Protein Subunits
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Repressor Proteins
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Saccharomyces cerevisiae Proteins
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TIM17 protein, S cerevisiae
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TIM23 protein, S cerevisiae
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TIM44 protein, S cerevisiae