Polypeptides traverse the mitochondrial envelope in an extended state.
Most mitochondrial proteins are synthesized as precursors in the cytosol and imported through contact sites between outer and inner mitochondrial membranes. The molecular mechanism of membrane translocation of precursor proteins is largely unclear. For this report, various hybrid proteins between portions of the precursor of cytochrome b2 and the entire dihydrofolate reductase (DHFR) were accumulated in mitochondrial contact sites. We unexpectedly found that about 50 amino acid residues of the polypeptide chain in transit were sufficient to span both membranes. This suggests a linear translocation of the polypeptide chain and presents evidence for a high degree of unfolding of polypeptides traversing the mitochondrial membranes.
Rassow
J
J
Institut für Physiologische Chemie, Universität München, FRG.
Hartl
F U
FU
Guiard
B
B
Pfanner
N
N
Neupert
W
W
D001692:Biological Transport; D007425:Intracellular Membranes / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D042844:L-Lactate Dehydrogenase (Cytochrome); D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D009492:Neurospora crassa; D011487:Protein Conformation; D011498:Protein Precursors / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D011506:Proteins / Q000378:metabolism* / Q000648:ultrastructure; D011993:Recombinant Fusion Proteins; D012441:Saccharomyces cerevisiae; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism
D011498:Protein Precursors; D011506:Proteins; D011993:Recombinant Fusion Proteins; D007770:L-Lactate Dehydrogenase; D042844:L-Lactate Dehydrogenase (Cytochrome); D013762:Tetrahydrofolate Dehydrogenase