title: αβ'-NAC cooperates with Sam37 to mediate early stages of mitochondrial protein import.
abstract: 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.
authors.affiliation: Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico.
authors.forename: José Carlos
authors.initials: JC
authors.lastname: Ponce-Rojas
authors.affiliation: Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico.
authors.forename: Maria Clara
authors.initials: MC
authors.lastname: Avendaño-Monsalve
authors.affiliation: Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico.
authors.forename: Armando Roberto
authors.initials: AR
authors.lastname: Yañez-Falcón
authors.affiliation: Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico.
authors.forename: Fabiola
authors.initials: F
authors.lastname: Jaimes-Miranda
authors.affiliation: Unidad de Genómica Avanzada (Langebio), Centro de Investigación y de Estudios Avanzados del IPN, Irapuato, Mexico.
authors.forename: Erika
authors.initials: E
authors.lastname: Garay
authors.affiliation: Departamento de Bioquímica y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico.
authors.forename: Francisco
authors.initials: F
authors.lastname: Torres-Quiroz
authors.affiliation: Unidad de Genómica Avanzada (Langebio), Centro de Investigación y de Estudios Avanzados del IPN, Irapuato, Mexico.
authors.forename: Alexander
authors.initials: A
authors.lastname: DeLuna
authors.affiliation: Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico.
authors.forename: Soledad
authors.initials: S
authors.lastname: Funes
mesh_terms: D001692:Biological Transport; D003600:Cytosol / Q000737:chemistry / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D008928:Mitochondria / Q000737:chemistry / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000737:chemistry* / Q000378:metabolism; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism*; D014176:Protein Biosynthesis / Q000235:genetics; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D012270:Ribosomes / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D033681:Mitochondrial Membrane Transport Proteins; D018832:Molecular Chaperones; D021122:Protein Subunits; C092812:SAM37 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C096099:nascent-polypeptide-associated complex
keywords: Sam37; mitochondria; mitochondrial biogenesis; nascent-polypeptide associated complex; protein import