title: Membrane and cytosolic components affecting transport of the precursor for ornithine carbamyltransferase into mitochondria.
abstract: A higher molecular weight precursor (Mr = 39,000) to the liver mitochondrial matrix enzyme, ornithine carbamyltransferase (Mr = 36,000), is imported and processed by heart mitochondria in vitro in a manner similar to liver mitochondria. In both systems, however, an additional 37-kDa ornithine carbamyltransferase polypeptide appears, but this arises from nonspecific events and, therefore, does not represent a bona fide intermediate in the overall processing sequence. Our experiments demonstrate that the outer mitochondrial membrane of mitochondria contains a protease-sensitive (5 micrograms of trypsin or chymotrypsin/ml, 15 min at 2 degrees C), salt-resistant (1.0 M KCl) protein which is required to maintain import functions. In addition, functional post-translational import requires a component of the reticulocyte lysate (i.e. cytosol) that is used for initially synthesizing precursor enzyme. The component is retained by Sephadex G-25. Import of Sephadex G-25-excluded precursor is restored by fresh reticulocyte lysate but not by a combination of other additives, including Mg2+, K+, ATP, ADP, Pi, succinate, and total translation mixture (minus lysate).
mesh_terms: D000818:Animals; D001692:Biological Transport; D002918:Chymotrypsin / Q000494:pharmacology; D004792:Enzyme Precursors / Q000378:metabolism*; D051379:Mice; D008929:Mitochondria, Heart / Q000201:enzymology*; D008930:Mitochondria, Liver / Q000201:enzymology; D008970:Molecular Weight; D009954:Ornithine Carbamoyltransferase / Q000235:genetics*; D014176:Protein Biosynthesis; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000235:genetics; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism; D014357:Trypsin / Q000494:pharmacology
chemical_list: D004792:Enzyme Precursors; D012333:RNA, Messenger; D009954:Ornithine Carbamoyltransferase; D002918:Chymotrypsin; D014357:Trypsin