Coupling of mitochondrial import and export translocases by receptor-mediated supercomplex formation.
The mitochondrial outer membrane harbors two protein translocases that are essential for cell viability: the translocase of the outer mitochondrial membrane (TOM) and the sorting and assembly machinery (SAM). The precursors of β-barrel proteins use both translocases-TOM for import to the intermembrane space and SAM for export into the outer ... membrane. It is unknown if the translocases cooperate and where the β-barrel of newly imported proteins is formed. We established a position-specific assay for monitoring β-barrel formation in vivo and in organello and demonstrated that the β-barrel was formed and membrane inserted while the precursor was bound to SAM. β-barrel formation was inhibited by SAM mutants and, unexpectedly, by mutants of the central import receptor, Tom22. We show that the cytosolic domain of Tom22 links TOM and SAM into a supercomplex, facilitating precursor transfer on the intermembrane space side. Our study reveals receptor-mediated coupling of import and export translocases as a means of precursor channeling.
Mesh Terms:
Mitochondria, Mitochondrial Membrane Transport Proteins, Mitochondrial Proteins, Mutation, Porins, Protein Folding, Protein Structure, Secondary, Protein Transport, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins
Mitochondria, Mitochondrial Membrane Transport Proteins, Mitochondrial Proteins, Mutation, Porins, Protein Folding, Protein Structure, Secondary, Protein Transport, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins
Cell
Date: Aug. 01, 2013
PubMed ID: 23911324
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