title: Effects of protein size on the rate of import of the precursors of aldehyde dehydrogenase and ornithine transcarbamylase into rat liver mitochondria.
abstract: It is known that a signal peptide is required for the import of a protein into mitochondrial matrix. It is also known that a signal peptide can be attached to any protein and allow it to be imported. We recently reported that the rate of import of rat liver mitochondrial aldehyde dehydrogenase precursor was slower than that of ornithine transcarbamylase precursor (Wang TTY, Farrés J, and Weiner H. Arch Biochem Biophys 272, 440-449, 1989). It was not known if the difference in the rate of import was related to the fact that the mature portion of aldehyde dehydrogenase is larger (500 amino acids compared with 322 amino acids) or because the signal peptides were different. We further showed that treatment of the mitochondria with alcohols caused an inhibition of the import of the precursor of aldehyde dehydrogenase but not that of ornithine transcarbamylase. In the present study we constructed chimeric proteins that contained the signal peptide from one precursor protein and the mature portion from the other. We found that the rate of import was related to the overall size of the precursor protein. Consistent with this observation was finding that a truncated aldehyde dehydrogenase precursor, which contained 317 amino acids, was imported more rapidly than was the authentic precursor. Consistent with this finding was the fact that butanol caused the inhibition of only the large precursor proteins. Thus, it appears that size of the protein being imported is a major determinant of the rate at which a precursor protein is imported into mitochondria.
authors.affiliation: Department of Biochemistry, Purdue University, W. Lafayette, Indiana 47907.
authors.forename: T T
authors.initials: TT
authors.lastname: Wang
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.forename: H
authors.initials: H
authors.lastname: Weiner
mesh_terms: D000444:Aldehyde Dehydrogenase / Q000235:genetics*; D000818:Animals; D002678:Chimera; D003001:Cloning, Molecular; D004792:Enzyme Precursors / Q000235:genetics*; D008930:Mitochondria, Liver / Q000502:physiology*; D008970:Molecular Weight; D009954:Ornithine Carbamoyltransferase / Q000235:genetics*; D014176:Protein Biosynthesis / Q000235:genetics; D021382:Protein Sorting Signals / Q000502:physiology*; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D014158:Transcription, Genetic / Q000235:genetics; D014178:Translocation, Genetic / Q000235:genetics
chemical_list: D004792:Enzyme Precursors; D021382:Protein Sorting Signals; D011506:Proteins; D000444:Aldehyde Dehydrogenase; D009954:Ornithine Carbamoyltransferase