Purification and identification of a cytosolic factor required for import of precursors of mitochondrial proteins into mitochondria.
A cytosolic factor required for import of the precursor of mitochondrial protein into mitochondria was purified to homogeneity from a rabbit reticulocyte lysate by affinity column chromatography using a synthetic peptide containing the presequence of ornithine amino-transferase as a ligand. The molecular mass of the purified protein was estimated as 28 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The import of precursors of ornithine aminotransferase and sulfite oxidase into mitochondria was inhibited by anti-28-kDa protein IgG raised in guinea pigs. This antibody also blocked the binding of these precursors to mitochondria. These results suggest that the 28-kDa protein is an essential component of the import machinery in the cytosol and that anti-28-kDa protein IgG blocked the binding of the precursor of ornithine aminotransferase to mitochondria, but not the penetration step. Therefore, the 28-kDa protein may be a factor that should be named the "targeting factor" for import of mitochondrial protein.
Ono
H
H
Department of Biochemistry, Yamagata University School of Medicine, Japan.
Tuboi
S
S
D000595:Amino Acid Sequence; D000818:Animals; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000276:immunology / Q000302:isolation & purification* / Q000378:metabolism; D007074:Immunoglobulin G / Q000276:immunology; D008928:Mitochondria / Q000378:metabolism*; D008969:Molecular Sequence Data; D009953:Ornithine-Oxo-Acid Transaminase / Q000378:metabolism*; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000378:metabolism; D010455:Peptides / Q000032:analysis / Q000138:chemical synthesis; D011498:Protein Precursors / Q000378:metabolism*; D011817:Rabbits; D000637:Transaminases / Q000378:metabolism*
D002352:Carrier Proteins; D007074:Immunoglobulin G; D010455:Peptides; D011498:Protein Precursors; D050862:Oxidoreductases Acting on Sulfur Group Donors; D000637:Transaminases; D009953:Ornithine-Oxo-Acid Transaminase