The Drosophila Melanogaster UMP-CMP Kinase cDNA Encodes an N-terminal Mitochondrial Import Signal

Biochem Biophys Res Commun. 2003 Nov 14;311(2):440-5. doi: 10.1016/j.bbrc.2003.10.018.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cells, Cultured
  • Cloning, Molecular / methods*
  • DNA, Complementary / genetics
  • DNA, Complementary / metabolism*
  • Drosophila melanogaster / enzymology*
  • Drosophila melanogaster / genetics
  • Gene Expression Regulation, Enzymologic / physiology*
  • Humans
  • Mitochondria / enzymology*
  • Mitochondria / genetics
  • Molecular Sequence Data
  • Nucleoside-Phosphate Kinase / chemistry
  • Nucleoside-Phosphate Kinase / genetics
  • Nucleoside-Phosphate Kinase / metabolism*
  • Phosphorylation
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Sequence Analysis, Protein
  • Signal Transduction / physiology*
  • Substrate Specificity

Substances

  • DNA, Complementary
  • Recombinant Proteins
  • cytidylate kinase
  • Nucleoside-Phosphate Kinase