Abstract
The translocase of the outer mitochondrial membrane (TOM complex) is the general entry gate into mitochondria for almost all imported proteins. A variety of specific receptors allow the TOM complex to recognize targeting signals of various precursor proteins that are transported along different import pathways. Aside from the well-characterized presequence receptors Tom20 and Tom22 a third TOM receptor, Tom70, binds proteins of the carrier family containing multiple transmembrane segments. Here we demonstrate that Tom70 directly binds to presequence peptides using a dedicated groove. A single point mutation in the cavity of this pocket (M551R) reduces the presequence binding affinity of Tom70 ten-fold and selectively impairs import of the presequence-containing precursor Mdl1 but not the ADP/ATP carrier (AAC). Hence Tom70 contributes to the presequence import pathway by recognition of the targeting signal of the Mdl1 precursor.
Keywords:
Mitochondria; Presequence; Protein import; Tom70.
Copyright © 2015 Elsevier B.V. All rights reserved.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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ATP-Binding Cassette Transporters / chemistry
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ATP-Binding Cassette Transporters / metabolism*
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Amino Acid Sequence
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Mitochondria / metabolism*
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Mitochondrial Membrane Transport Proteins / chemistry*
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Mitochondrial Membrane Transport Proteins / genetics
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Mitochondrial Membrane Transport Proteins / metabolism*
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Mitochondrial Precursor Protein Import Complex Proteins
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Models, Molecular
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Organisms, Genetically Modified
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Protein Binding / genetics
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Protein Folding
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Protein Interaction Domains and Motifs* / genetics
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Protein Precursors / chemistry
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Protein Precursors / metabolism
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Protein Sorting Signals* / genetics
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Protein Structure, Secondary / genetics
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Protein Transport / genetics
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / ultrastructure
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Saccharomyces cerevisiae Proteins / chemistry*
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Saccharomyces cerevisiae Proteins / genetics
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Saccharomyces cerevisiae Proteins / metabolism*
Substances
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ATP-Binding Cassette Transporters
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MDL1 protein, S cerevisiae
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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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Saccharomyces cerevisiae Proteins
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TOM70 protein, S cerevisiae