title: Topogenesis of cytochrome oxidase subunit II. Mechanisms of protein export from the mitochondrial matrix.
abstract: Cytochrome c oxidase subunit II (COXII) in yeast mitochondria is synthesized as a precursor (preCOXII) and is sorted across the inner membrane, whereby both N and C termini become exposed to the intermembrane space. We describe here how this process can be experimentally dissected into a number of distinct stages. Our results demonstrate that the translation of COXII is not obligatorily coupled to translocation. Insertion into the inner membrane and export of the N- and C-terminal domains require an energized inner membrane. The export of COXII is independent of both maturation by the Imp1p protease and assembly into the cytochrome c oxidase complex. When linked to a mitochondrial matrix-targeting sequence, the N-terminal portion of preCOXII (fused to mouse dihydrofolate reductase) can be imported into the mitochondrial matrix. Following accumulation in the matrix, this chimeric protein can become exported across the inner membrane, delivering the N terminus into the intermembrane space where it undergoes processing by the Imp1p protease. This export process displays a number of similarities to bacterial protein export and supports the view that the principles of sorting are conserved from prokaryotes to eukaryotic organelles.
authors.affiliation: Institut für Physiologische Chemie, Universität München, Germany.
authors.forename: J M
authors.initials: JM
authors.lastname: Herrmann
authors.forename: H
authors.initials: H
authors.lastname: Koll
authors.forename: R A
authors.initials: RA
authors.lastname: Cook
authors.forename: W
authors.initials: W
authors.lastname: Neupert
authors.forename: R A
authors.initials: RA
authors.lastname: Stuart
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004792:Enzyme Precursors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008564:Membrane Potentials; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D008954:Models, Biological; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics; D013762:Tetrahydrofolate Dehydrogenase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D004792:Enzyme Precursors; D011993:Recombinant Fusion Proteins; D013762:Tetrahydrofolate Dehydrogenase; D003576:Electron Transport Complex IV