The Drosophila melanogaster UMP-CMP kinase cDNA encodes an N-terminal mitochondrial import signal.
Drosophila melanogaster cells express a multi-substrate deoxyribonucleoside kinase that phosphorylates both purine and pyrimidine deoxyribonucleosides. The subsequent phosphorylation step is catalyzed by nucleoside monophosphate kinases. We have cloned and characterized the D. melanogaster UMP-CMP kinase (Dm.UMP-CMP kinase) to further study the nucleotide metabolizing enzymes in these cells. The kinase, encoded by the dak1 gene, was approximately 60% similar to the human UMP-CMP kinase and predominantly phosphorylated CMP, dCMP, and UMP. Expression analysis showed that the Dm.UMP-CMP kinase mRNA was constitutively expressed throughout the Drosophila development. The open-reading frame of the Dm.UMP-CMP kinase cDNA was extended in the 5'-region compared to UMP-CMP kinases of other species. The extended region encoded an N-terminal sequence with properties characteristic of a mitochondrial import signal. Expression of the enzyme in fusion with the green fluorescent protein verified that the N-terminal signal targeted the enzyme to mitochondria. This is the first time a mitochondrial pyrimidine nucleoside monophosphate kinase has been cloned from any organism and we discuss the implication of this finding for deoxyribonucleoside salvage in both Drosophila and other organisms.
Division of Clinical Virology F68, Karolinska Institute, Huddinge University Hospital, S-14186 Stockholm, Sweden. Sophie.Curbo@labmed.ki.se
Sophie
S
Curbo
Marjan
M
Amiri
Fariba
F
Foroogh
Magnus
M
Johansson
Anna
A
Karlsson
D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D003001:Cloning, Molecular / Q000379:methods*; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000201:enzymology* / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D006801:Humans; D008928:Mitochondria / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D009703:Nucleoside-Phosphate Kinase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D020539:Sequence Analysis, Protein; D015398:Signal Transduction / Q000502:physiology*; D013379:Substrate Specificity
D018076:DNA, Complementary; D011994:Recombinant Proteins; C019979:cytidylate kinase; D009703:Nucleoside-Phosphate Kinase