title: Mutations in a 19-amino-acid hydrophobic region of the yeast cytochrome c1 presequence prevent sorting to the mitochondrial intermembrane space.
abstract: Most mitochondrial proteins destined for the intermembrane space (IMS) carry in their presequence information for localization to the IMS in addition to information for their import. By selecting for mutants in the yeast Saccharomyces cerevisiae that mislocalize an IMS-targeted fusion protein, we identified mutations in the IMS sorting signal of the cytochrome c1 protein. Amino acid substitutions or deletions in a stretch of 19 hydrophobic amino acids of the cytochrome c1 presequence resulted in accumulation of the intermediate form of the cytochrome c1 protein in the matrix. In some cases, the accumulated intermediate appeared to be slowly exported from the matrix, across the inner membrane to the IMS. Our results support the hypothesis that the cytochrome c1 precursor is normally imported completely into the matrix and then exported to the IMS.
authors.affiliation: Department of Cell Biology and Anatomy, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
authors.forename: R E
authors.initials: RE
authors.lastname: Jensen
authors.forename: S
authors.initials: S
authors.lastname: Schmidt
authors.forename: R J
authors.initials: RJ
authors.lastname: Mark
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001692:Biological Transport; D003575:Cytochromes c1 / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D004271:DNA, Fungal; D007425:Intracellular Membranes / Q000378:metabolism; D007700:Kinetics; D008928:Mitochondria / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism; D021382:Protein Sorting Signals / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics*; D014867:Water / Q000737:chemistry
chemical_list: D004271:DNA, Fungal; D011498:Protein Precursors; D021382:Protein Sorting Signals; D014867:Water; D003575:Cytochromes c1