MPI1, an essential gene encoding a mitochondrial membrane protein, is possibly involved in protein import into yeast mitochondria.
To identify components of the mitochondrial protein import pathway in yeast, we have adopted a positive selection procedure for isolating mutants disturbed in protein import. We have cloned and sequenced a gene, termed MPI1, that can rescue the genetic defect of one group of these mutants. MPI1 encodes a hydrophilic 48.8 kDa protein that is essential for cell viability. Mpi1p is a low abundance and constitutively expressed mitochondrial protein. Mpi1p is synthesized with a characteristic mitochondrial targeting sequence at its amino-terminus, which is most probably proteolytically removed during import. It is a membrane protein, oriented with its carboxy-terminus facing the intermembrane space. In cells depleted of Mpi1p activity, import of the precursor proteins that we tested thus far, is arrested. We speculate that the Mpi1 protein is a component of a proteinaceous import channel for translocation of precursor proteins across the mitochondrial inner membrane.
Maarse
A C
AC
Department of Molecular Cell Biology, University of Amsterdam, The Netherlands.
Blom
J
J
Grivell
L A
LA
Meijer
M
M
D000595:Amino Acid Sequence; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D004271:DNA, Fungal / Q000235:genetics / Q000378:metabolism; D005800:Genes, Fungal; D005808:Genes, Recessive; D005838:Genotype; D007425:Intracellular Membranes / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016296:Mutagenesis; D010641:Phenotype; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism
D002352:Carrier Proteins; D004271:DNA, Fungal; D008565:Membrane Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; C077016:TIM44 protein, S cerevisiae; D013482:Superoxide Dismutase