Identification of a novel nuclear-localized adenylate kinase from Drosophila melanogaster.

As a step to further understand the role of adenylate kinase (AK) in the energy metabolism network, we identified, purified, and characterized a previously undescribed adenylate kinase in Drosophila melanogaster. The cDNA encodes a 175-amino acid protein, which shows 47.85% identity in 163 amino acids to human AK6. The recombinant protein was successfully expressed in Escherichia coli BL21(DE3) strain. Characterization of this protein by enzyme activity assay showed adenylate kinase activity. AMP and CMP were the preferred substrates, and UMP can also be phosphorylated to some extent, with ATP as the best phosphate donor. Subcellular localization study showed a predominantly nuclear localization. Therefore, based on the substrate specificity, the specific nuclear localization in the cell, and the sequence similarity with human AK6, we named this novel adenylate kinase identified from the fly DAK6.