The N-terminal extension of the ADP/ATP translocator is not involved in targeting to plant mitochondria in vivo.
The mitochondrial ADP/ATP translocator, also called adenine nucleotide translocase (ANT), is synthesized in plants with an N-terminal extension which is cleaved upon import into mitochondria. In contrast, the homologous proteins of mammals or fungi do not contain such a transient amino terminal presequence. To investigate whether the N-terminal extension is needed for correct intracellular sorting in vivo, translational fusions were constructed of the translocator cDNA--with and without presequence--with the beta-glucuronidase (gus) reporter gene. The distribution of reporter enzymatic activity in the subcellular compartments of transgenic plants and transformed yeast cells was subsequently analysed. The results show that: (i) the plant translocator presequence is not necessary for the correct localization of the ANT to the mitochondria; (ii) the mitochondrial targeting information contained in the mature part of the protein is sufficient to overcome, to some extent, the presence of plastid transit peptides; and (iii) the presequence alone is not able to target a passenger protein to mitochondria in vivo.
Mozo
T
T
Institut für Genbiologische Forschung Berlin GmbH, Germany.
Fischer
K
K
Flügge
U I
UI
Schmitz
U K
UK
D001483:Base Sequence; D018744:DNA, Plant; D005966:Glucuronidase / Q000235:genetics; D008928:Mitochondria / Q000378:metabolism*; D000226:Mitochondrial ADP, ATP Translocases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified; D021382:Protein Sorting Signals / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D011198:Solanum tuberosum / Q000235:genetics / Q000378:metabolism*
D018744:DNA, Plant; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D000226:Mitochondrial ADP, ATP Translocases; D005966:Glucuronidase