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αβ′‐NAC cooperates with Sam37 to mediate early stages of mitochondrial protein import
Author(s) -
PonceRojas José Carlos,
AvendañoMonsalve Maria Clara,
YañezFalcón Armando Roberto,
JaimesMiranda Fabiola,
Garay Erika,
TorresQuiroz Francisco,
DeLuna Alexander,
Funes Soledad
Publication year - 2017
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.14024
Subject(s) - cytosol , protein targeting , mitochondrion , microbiology and biotechnology , protein subunit , mitochondrial carrier , chaperone (clinical) , biology , translocase of the inner membrane , saccharomyces cerevisiae , mitochondrial membrane transport protein , ribosome , organelle , inner mitochondrial membrane , transport protein , biochemistry , translocase of the outer membrane , nuclear gene , membrane protein , mitochondrial dna , gene , bacterial outer membrane , membrane , medicine , rna , escherichia coli , pathology , enzyme
The mitochondrial proteome is mostly composed of nuclear‐encoded proteins. Such polypeptides are synthesized with signals that guide their intracellular transport to the surface of the organelle and later within the different mitochondrial subcompartments until they reach their functional destination. It has been suggested that the nascent‐polypeptide associated complex ( NAC ) – a cytosolic chaperone that recognizes nascent chains on translationally active ribosomes – has a role in the import of nuclear‐encoded mitochondrial proteins. However, the molecular mechanisms that regulate the NAC ‐mediated cotranslational import are still not clear. Here, we show that a particular NAC heterodimer formed by subunits α and β′ in Saccharomyces cerevisiae is specifically involved in the process of mitochondrial import and functionally cooperates with Sam37, an outer membrane protein subunit of the sorting and assembly machinery complex. Mutants in both components display growth defects, incorrectly accumulate precursor forms of mitochondrial proteins in the cytosol, and have an altered mitochondrial protein content. We propose that αβ′‐ NAC and Sam37 are members of the system that recognizes mitochondrial proteins at early stages of their synthesis, escorting them to the import machinery of mitochondria.