alpha beta%26apos;-NAC cooperates with Sam37 to mediate early stages of mitochondrial protein import

作者：Carlos Ponce Rojas Jose; Clara Avendano Monsalve Maria; Yanez Falcon Armando Roberto; Jaimes Miranda Fabiola; Garay Erika; Torres Quiroz Francisco; DeLuna Alexander; Funes Soledad

来源：FEBS Journal, 2017, 284(5): 814-830.

DOI：10.1111/febs.14024

• mitochondria
• mitochondrial biogenesis
• nascent-polypeptide associated complex
• protein import
• Sam37

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 alpha and beta' 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 alpha beta'-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.

• 出版日期2017-3