title: Protein folding causes an arrest of preprotein translocation into mitochondria in vivo.
abstract: With vital yeast cells, a hybrid protein consisting of the amino-terminal third of the precursor to cytochrome b2 and of the entire dihydrofolate reductase was arrested on the import pathway into mitochondria. Accumulation of the protein in the mitochondrial membranes was achieved by inducing a stable tertiary structure of the dihydrofolate reductase domain. Thereby, three salient features of mitochondrial protein uptake in vivo were demonstrated: its posttranslational character; the requirement for unfolding of precursors; and import through translocation contact sites. The permanent occupation of translocation sites by the fusion protein inhibited the import of other precursors; it did, however, not lead to leakage of mitochondrial ions, implying the existence of a channel that is sealed around the membrane spanning polypeptide segment.
authors.affiliation: Institut für Physiologische Chemie, Universität München, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Wienhues
authors.forename: K
authors.initials: K
authors.lastname: Becker
authors.forename: M
authors.initials: M
authors.lastname: Schleyer
authors.forename: B
authors.initials: B
authors.lastname: Guiard
authors.forename: M
authors.initials: M
authors.lastname: Tropschug
authors.forename: A L
authors.initials: AL
authors.lastname: Horwich
authors.forename: N
authors.initials: N
authors.lastname: Pfanner
authors.forename: W
authors.initials: W
authors.lastname: Neupert
mesh_terms: D000630:Aminopterin / Q000494:pharmacology; D001692:Biological Transport; D007425:Intracellular Membranes / Q000378:metabolism; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D042844:L-Lactate Dehydrogenase (Cytochrome); D008564:Membrane Potentials; D008928:Mitochondria / Q000378:metabolism*; D011487:Protein Conformation; D011498:Protein Precursors / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000378:metabolism; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism
chemical_list: D011498:Protein Precursors; D011993:Recombinant Fusion Proteins; D007770:L-Lactate Dehydrogenase; D042844:L-Lactate Dehydrogenase (Cytochrome); D013762:Tetrahydrofolate Dehydrogenase; D000630:Aminopterin