title: Reconstitution of the initial steps of mitochondrial protein import.
abstract: We have reconstituted the initial steps of mitochondrial protein import with a purified precursor protein, a purified, ATP-dependent, cytosolic chaperone selective for mitochondrial precursors (mitochondrial import stimulating factor; MSF), and either intact mitochondria or intact or solubilized mitochondrial outer membranes. We show that the precursor-MSF complex first binds to the Mas37p/Mas70p subunits of the mitochondrial import receptor. After ATP-dependent release of MSF, the precursor is transferred from Mas37p/Mas70p to the Mas20p/Mas22p subunits of the receptor, and finally delivered to the import channel in the outer membrane. Import in the absence of the MSF bypasses Mas37p/Mas70p. The ATP-mediated transfer of a precursor from MSF to specific subunits of the import receptor is similar to the GTP-mediated transfer of precursors from the signal recognition particle to its receptor on the endoplasmic reticulum.
authors.affiliation: Department of Molecular Biology, Graduate School of Medical Science, Kyushu University, Fukuoka, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Hachiya
authors.forename: K
authors.initials: K
authors.lastname: Mihara
authors.forename: K
authors.initials: K
authors.lastname: Suda
authors.forename: M
authors.initials: M
authors.lastname: Horst
authors.forename: G
authors.initials: G
authors.lastname: Schatz
authors.forename: T
authors.initials: T
authors.lastname: Lithgow
mesh_terms: D048948:14-3-3 Proteins; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000325:Adrenodoxin / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D018832:Molecular Chaperones / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D000099221:Protein Kinase C zeta
chemical_list: D048948:14-3-3 Proteins; D000251:Adenosine Triphosphatases; D000325:Adrenodoxin; D005656:Fungal Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D018832:Molecular Chaperones; D011498:Protein Precursors; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D029701:Saccharomyces cerevisiae Proteins; C490392:Prkcz protein, rat; D000099221:Protein Kinase C zeta; C092812:SAM37 protein, S cerevisiae; C489350:TOM20 protein, S cerevisiae; C090857:TOM22 protein, S cerevisiae; C489039:TOM70 protein, S cerevisiae; C489998:Tomm20 protein, rat; C490391:Ywhaz protein, rat; C044938:preadrenodoxin; C090759:mitochondrial import stimulation factor, rat