Arginine in the leader peptide is required for both import and proteolytic cleavage of a mitochondrial precursor.
Most mitochondrial proteins are encoded in the nucleus and translated in the cytoplasm as larger precursors containing NH2-terminal "leader" peptides, which are strikingly basic in overall amino acid composition. Recent experiments indicate that these leader peptides are both necessary and sufficient to direct post-translational recognition and import of precursors by mitochondria. In this report, we demonstrate a critical role for one or more of the basic arginine residues in the leader peptide of the subunit precursor for the human mitochondrial matrix enzyme, ornithine transcarbamoylase (ornithine carbamoyltransferase, carbamoylphosphate: L-ornithine carbamoyltransferase, EC 2.1.3.3). The distal three of four basic residues, all arginines, in the leader peptide of ornithine transcarbamoylase were replaced at once with charge-neutral glycine residues. The altered ornithine transcarbamoylase precursor failed to be taken up by intact mitochondria in vitro. Moreover, it also failed to be proteolytically cleaved upon incubation with a mitochondrial matrix fraction containing the Zn2+-dependent protease, which normally cleaves the leader peptide.
D000595:Amino Acid Sequence; D001120:Arginine / Q000502:physiology*; D001692:Biological Transport; D010450:Endopeptidases / Q000378:metabolism; D004792:Enzyme Precursors / Q000378:metabolism*; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D008565:Membrane Proteins; D008928:Mitochondria / Q000378:metabolism*; D009154:Mutation; D009954:Ornithine Carbamoyltransferase / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D010957:Plasmids; D021382:Protein Sorting Signals; D012697:Serine Endopeptidases; D013329:Structure-Activity Relationship
D004792:Enzyme Precursors; D008565:Membrane Proteins; D010455:Peptides; D021382:Protein Sorting Signals; D001120:Arginine; D009954:Ornithine Carbamoyltransferase; D010450:Endopeptidases; D012697:Serine Endopeptidases; C026515:type I signal peptidase