title: N-terminal domain of the dual-targeted pea glutathione reductase signal peptide controls organellar targeting efficiency.
abstract: Import of nuclear-encoded proteins into mitochondria and chloroplasts is generally organelle specific and its specificity depends on the N-terminal signal peptide. Yet, a group of proteins known as dual-targeted proteins have a targeting peptide capable of leading the mature protein to both organelles. We have investigated the domain structure of the dual-targeted pea glutathione reductase (GR) signal peptide by using N-terminal truncations. A mutant of the GR precursor (pGR) starting with the second methionine residue of the targeting peptide, pGRdelta2-4, directed import into both organelles, negating the possibility that dual import was controlled by the nature of the N terminus. The deletion of the 30 N-terminal residues (pGRdelta2-30) inhibited import efficiency into chloroplasts substantially and almost completely into mitochondria, whereas the removal of only 16 N-terminal amino acid residues (pGRdelta2-16) resulted in the strongly stimulated mitochondrial import without significantly affecting chloroplast import. Furthermore, N-terminal truncations of the signal peptide (pGRdelta2-16 and pGRdelta2-30) greatly stimulated the mitochondrial processing activity measured with the isolated processing peptidase. These results suggest a domain structure for the dual-targeting peptide of pGR and the existence of domains controlling organellar import efficiency therein.
authors.affiliation: Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, S-106 91 Stockholm, Sweden.
authors.forename: Charlotta
authors.initials: C
authors.lastname: Rudhe
authors.forename: Rachel
authors.initials: R
authors.lastname: Clifton
authors.forename: James
authors.initials: J
authors.lastname: Whelan
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Glaser
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002736:Chloroplasts / Q000201:enzymology / Q000378:metabolism; D004792:Enzyme Precursors / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D005980:Glutathione Reductase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008666:Metalloendopeptidases / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D018532:Pisum sativum / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018515:Plant Leaves / Q000166:cytology; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000187:drug effects; D017384:Sequence Deletion; D013025:Glycine max / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D018724:Spinacia oleracea / Q000166:cytology; D014634:Valinomycin / Q000494:pharmacology; D000096122:Mitochondrial Processing Peptidase
chemical_list: D000900:Anti-Bacterial Agents; D004792:Enzyme Precursors; D005980:Glutathione Reductase; D008666:Metalloendopeptidases; D010446:Peptide Fragments; D010940:Plant Proteins; D021382:Protein Sorting Signals; D014634:Valinomycin; D000096122:Mitochondrial Processing Peptidase