title: A signal-anchor sequence selective for the mitochondrial outer membrane.
abstract: pOMD29 is a hybrid protein containing the NH2-terminal topogenic sequence of a bitopic, integral protein of the outer mitochondrial membrane in yeast, OMM70, fused to dihydrofolate reductase. The topogenic sequence consists of two structural domains: an NH2-terminal basic region (amino acids 1-10) and an apolar region which is the predicted transmembrane segment (amino acids 11-29). The transmembrane segment alone was capable of targeting and inserting the hybrid protein into the outer membrane of intact mitochondria from rat heart in vitro. The presence of amino acids 1-10 enhanced the rate of import, and this increased rate depended, in part, on the basic amino acids located at positions 2, 7, and 9. Deletion of a large portion of the transmembrane segment (amino acids 16-29) resulted in a protein that exhibited negligible import in vitro. Insertion of pOMD29 into the outer membrane was not competed by import of excess precursor protein destined for the mitochondrial matrix, indicating that the two proteins may have different rate-limiting steps during import. We propose that the structural domains within amino acids 1-29 of pOMD29 cooperate to form a signal-anchor sequence, the characteristics of which suggest a model for proper sorting to the mitochondrial outer membrane.
authors.affiliation: Department of Biochemistry, McGill University, Montreal, Canada.
authors.forename: H M
authors.initials: HM
authors.lastname: McBride
authors.forename: D G
authors.initials: DG
authors.lastname: Millar
authors.forename: J M
authors.initials: JM
authors.lastname: Li
authors.forename: G C
authors.initials: GC
authors.lastname: Shore
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001692:Biological Transport; D002451:Cell Compartmentation; D004252:DNA Mutational Analysis; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015789:HLA-A2 Antigen / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D008969:Molecular Sequence Data; D021382:Protein Sorting Signals / Q000235:genetics / Q000378:metabolism*; D017433:Protein Structure, Secondary; D051381:Rats; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D013329:Structure-Activity Relationship; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D015789:HLA-A2 Antigen; D008565:Membrane Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D021382:Protein Sorting Signals; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; C489039:TOM70 protein, S cerevisiae; D013762:Tetrahydrofolate Dehydrogenase