Abstract
We have previously isolated cDNA clones for the gip17 gene encoding the cytosolic nucleoside diphosphate (NDP) kinase from Dictyostelium discoideum, and partial cDNAs for guk, a second member of the NDP kinase gene family (Wallet, V., Mutzel, R., Troll, H., Barzu, O., Wurster, B., Véron, M., and Lacombe, M. L. (1990) J. Natl. Cancer Inst. 80, 1199-1202). We now characterize genomic DNA clones for both NDP kinase genes, and we show that guk defines a nuclear-encoded mitochondrial NDP kinase. Isolated D. discoideum mitochondria contain 3% of the total cellular NDP kinase activity. Antibodies which specifically recognize and inhibit the activity of either cytosolic or mitochondrial NDP kinase unambiguously distinguish between these activities. The nascent mitochondrial NDP kinase contains a presequence of 57 amino acids that is removed during import into the organelle as shown by determination of the NH2 terminus of the mature protein from mitochondria. The genes for mitochondrial and cytosolic NDP kinases contain four and two introns, respectively. The positions of the of the introns in the gene for the cytosolic enzyme match exactly the positions of the second and fourth introns in the coding region of its mitochondrial homologue. From these results we conclude that the isozymes diverged from a common ancestor, and we discuss possible phylogenetic pathways for the evolution of cytosolic and organelle NDP kinases.
Highlights
nucleoside diphosphate (NDP) kinase genes, and we show that guk defines a nuclear-encoded mitochondrial NDP kinase
In order to analyze thenatureand possible functional significance of this second NDP kinase gene, we have determined its structure, and we show that it encodes the mitochondrial NDP kinase from D.discoideum
We report the isolation of a Dictyostelium gene encoding a mitochondrial NDP kinase, the first mitochondrial member of this enzyme family that hasbecome accessible to molecular analysis
Summary
NDP kinase genes, and we show that guk defines a nuclear-encoded mitochondrial NDP kinase. The nascent mitodevelopment (Dearolf et al, 1988) encodes an NDP kinase (Biggset al.,1990).The human gene nm23-HI which is highly expressed in proliferating malignant cells (Keim et al.,1992; Hailat et al, 1991; Lacombe et al, 1991) and which may be involved in tumor metastasis (Rosengard et al.,1989; Leone et al.,1991) encodes an NDP kinase (Gilles et al.,1991). Both Awd, Nm23-H1, and asecond isozymeencodedby nm23-. In Drosophila the awd gene involved in kinases is the cellular pteridine metabolism; the develop-
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