Overexpression of yeast karyopherin Pse1p/Kap121p stimulates the mitochondrial import of hydrophobic proteins in vivo.
During evolution, cellular processes leading to the transfer of genetic information failed to send all the mitochondrial genes into the nuclear genome. Two mitochondrial genes are still exclusively located in the mitochondrial genome of all living organisms. They code for two highly hydrophobic proteins: the apocytochrome b and the subunit I of cytochrome oxidase. Assuming that the translocation machinery could not efficiently transport long hydrophobic fragments, we searched for multicopy suppressors of this physical blockage. We demonstrated that overexpression of Pse1p/Kap121p or Kap123p, which belong to the superfamily of karyopherin beta proteins, facilitates the translocation of chimeric proteins containing several stretches of apocytochrome b fused to a reporter mitochondrial gene. The effect of PSE1/KAP121 overexpression (in which PSE1 is protein secretion enhancer 1) on mitochondrial import of the chimera is correlated with an enrichment of the corresponding transcript in cytoplasmic ribosomes associated with mitochondria. PSE1/KAP121 overexpression also improves the import of the hydrophobic protein Atm1p, an ABC transporter of the mitochondrial inner membrane. These results suggest that in vivo PSE1/KAP121 overexpression facilitates, either directly or indirectly, the co-translational import of hydrophobic proteins into mitochondria.
Corral-Debrinski
M
M
Ecole Normale Supérieure, Laboratoire de Génétique Moléculaire URA CNRS 1302, Paris, France.
Belgareh
N
N
Blugeon
C
C
Claros
M G
MG
Doye
V
V
Jacq
C
C
D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D001059:Apoproteins / Q000378:metabolism; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000378:metabolism; D003573:Cytochrome b Group / Q000378:metabolism; D045303:Cytochromes b; D017931:DNA Primers; D019286:Endopeptidase K / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins; D008928:Mitochondria / Q000378:metabolism*; D008954:Models, Biological; D005810:Multigene Family / Q000235:genetics; D016296:Mutagenesis; D009685:Nuclear Envelope / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D010101:Oxygen Consumption; D010641:Phenotype; D014176:Protein Biosynthesis; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics*; D012270:Ribosomes / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D014178:Translocation, Genetic; D028961:beta Karyopherins
D018528:ATP-Binding Cassette Transporters; D001059:Apoproteins; D002352:Carrier Proteins; D003573:Cytochrome b Group; D017931:DNA Primers; D008164:Luminescent Proteins; D026901:Membrane Transport Proteins; D009687:Nuclear Proteins; C483822:PSE1 protein, S cerevisiae; D018160:Receptors, Cytoplasmic and Nuclear; D029701:Saccharomyces cerevisiae Proteins; D028961:beta Karyopherins; D049452:Green Fluorescent Proteins; D045303:Cytochromes b; D019286:Endopeptidase K; D005947:Glucose; D005990:Glycerol