Acidic receptor domains on both sides of the outer membrane mediate translocation of precursor proteins into yeast mitochondria.
Mitochondrial precursor proteins made in the cytosol bind to a hetero-oligomeric protein import receptor on the mitochondrial surface and then pass through the translocation channel across the outer membrane. This translocation step is accelerated by an acidic domain of the receptor subunit Mas22p, which protrudes into the intermembrane space. This 'trans' domain of Mas22p specifically binds functional mitochondrial targeting peptides with a Kd of < 1 microM and is required to anchor the N-terminal targeting sequence of a translocation-arrested precursor in the intermembrane space. If this Mas22p domain is deleted, respiration-driven growth of the cells is compromised and import of different precursors into isolated mitochondria is inhibited 3- to 8-fold. Binding of precursors to the mitochondrial surface appears to be mediated by cytosolically exposed acidic domains of the receptor subunits Mas20p and Mas22p. Translocation of a precursor across the outer membrane thus appears to involve sequential binding of the precursor's basic and amphiphilic targeting signal to acidic receptor domains on both sides of the membrane.
Bolliger
L
L
Biozentrum, Universität Basel, Switzerland.
Junne
T
T
Schatz
G
G
Lithgow
T
T
D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D001693:Biological Transport, Active; D003600:Cytosol / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D004271:DNA, Fungal / Q000235:genetics; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007425:Intracellular Membranes / Q000737:chemistry / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008928:Mitochondria / Q000737:chemistry / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins; D008969:Molecular Sequence Data; D011498:Protein Precursors / Q000378:metabolism*; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D017384:Sequence Deletion
D017931:DNA Primers; D004271:DNA, Fungal; D005656:Fungal Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D011498:Protein Precursors; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; C090857:TOM22 protein, S cerevisiae