The pea mitochondrial nucleoside diphosphate kinase cleaves DNA and RNA

Here, we present the characterization of a plant NDPK exhibiting nuclease activity. This is the first identification of a nuclease localised in the intermembrane space of plant mitochondria. The recombinant pea NDPK3 protein cleaves not only supercoiled plasmid DNA, but also highly structured RNA molecules such as tRNAs or the 3'UTR of the atp9 mRNA suggesting that the NDPK3 nuclease activity has a structural requirement. ATP inhibits this nuclease activity, while ADP has no effect. Furthermore, studies on NDPK mutant proteins indicate that the nuclease- and the kinase-mechanisms are separate.