Mitochondria can import artificial precursor proteins containing a branched polypeptide chain or a carboxy-terminal stilbene disulfonate.
A purified, artificial precursor protein was used as a transport vehicle to test the tolerance of the mitochondrial protein import system. The precursor was a fusion protein consisting of mouse dihydrofolate reductase linked to a yeast mitochondrial presequence; it contained a unique cysteine as its COOH-terminal residue. This COOH-terminal cysteine was covalently coupled to either a stilbene disulfonate derivative or, with the aid of a bifunctional cross-linker, to one of the free amino groups of horse heart cytochrome c. Coupling to horse heart cytochrome c generated a mixture of branched polypeptide chains since this cytochrome lacks a free alpha-amino group. Both adducts were imported and cleaved by isolated yeast mitochondria. The mitochondrial protein import machinery can thus transport more complex structures and even highly charged "membrane-impermeant" organic molecules. This suggests that transport occurs through a hydrophilic environment.
Vestweber
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D
University of Basel, Department of Biochemistry, Switzerland.
Schatz
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G
D001692:Biological Transport; D003574:Cytochrome c Group / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism*; D007700:Kinetics; D008928:Mitochondria / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism* / Q000648:ultrastructure; D011993:Recombinant Fusion Proteins / Q000378:metabolism / Q000648:ultrastructure; D012441:Saccharomyces cerevisiae; D013267:Stilbenes / Q000378:metabolism; D013329:Structure-Activity Relationship; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism
D003574:Cytochrome c Group; D011498:Protein Precursors; D011993:Recombinant Fusion Proteins; D013267:Stilbenes; D013762:Tetrahydrofolate Dehydrogenase; D003576:Electron Transport Complex IV