αβ'-NAC cooperates with Sam37 to mediate early stages of mitochondrial protein import.

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 sub-compartments until they reach their functional destination. It has been suggested that NAC - a cytosolic chaperone which ...
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 co-translational 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 SAM 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 machineries of mitochondria. This article is protected by copyright. All rights reserved.
FEBS J.
Date: Jan. 21, 2017
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