title: Tom34 unlike Tom20 does not interact with the leader sequences of mitochondrial precursor proteins.
abstract: Tom20 and Tom34 are mammalian liver proteins previously identified by others to be components of the mitochondrial import translocation apparatus. It has been shown that Tom20 interacts with the leader sequence of nuclear coded matrix space precursor proteins. Here we show with recombinantly expressed Tom proteins that Tom34 binds the mature portion of the precursor and not the leader. Both these Tom proteins inhibited the import of newly translated precursor of aldehyde dehydrogenase in an in vitro assay. Only Tom20 inhibited the import of a fusion protein of the leader of aldehyde dehydrogenase attached to dihydrofolate reductase. Antibodies against Tom20 coprecipitated both the precursor of aldehyde dehydrogenase (pALDH) and of dihydrofolate reductase (pA-DHFR). Antibodies against Tom34 interacted only when the mature portion of aldehyde dehydrogenase was present. Similar import inhibition patterns were found when other precursor and chimeric constructs we investigated. When Tom34-green fluorescence protein was transfected to HeLa cells it was observed that Tom34 was found through out the cell. It is concluded from our observation that Tom34 is a cytosolic protein, whose role appeared to be to interact with mature portion of some preproteins and may keep them in an unfolded, import compatible state.
authors.affiliation: Department of Biochemistry, Purdue University, 1153 Biochemistry Building, West Lafayette, Indiana 47907-1153, USA.
authors.forename: Abhijit
authors.initials: A
authors.lastname: Mukhopadhyay
authors.forename: Larisa V
authors.initials: LV
authors.lastname: Avramova
authors.forename: Henry
authors.initials: H
authors.lastname: Weiner
mesh_terms: D020121:5' Untranslated Regions; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000444:Aldehyde Dehydrogenase / Q000378:metabolism; D000080924:Aldehyde Dehydrogenase 1 Family; D000595:Amino Acid Sequence; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D008164:Luminescent Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D014176:Protein Biosynthesis; D011487:Protein Conformation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D050697:Retinal Dehydrogenase; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism; D014162:Transfection
chemical_list: D020121:5' Untranslated Regions; D002352:Carrier Proteins; D018076:DNA, Complementary; D007527:Isoenzymes; D008164:Luminescent Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D010455:Peptides; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; C084008:TOMM20 protein, human; C108485:TOMM34 protein, human; D049452:Green Fluorescent Proteins; D000080924:Aldehyde Dehydrogenase 1 Family; D000444:Aldehyde Dehydrogenase; C510223:ALDH1A1 protein, human; D050697:Retinal Dehydrogenase; D013762:Tetrahydrofolate Dehydrogenase; D000251:Adenosine Triphosphatases