The function of ENSG00000172113 (NME6, NME/NM23 nucleoside diphosphate kinase 6) is as follows. Catalytic subunit of a complex with RCC1L, which catalyzes the transfer of a gamma-phosphoryl group from a nucleoside triphosphate, mainly ATP, to a nucleoside diphosphate via a ping-pong mechanism involving the formation of a phosphohistidine intermediate (PubMed:10618642, PubMed:34789336, PubMed:37770567). Participates in the regulation of mitochondrial nucleotide levels, mitoribosome biogenesis, and mitochondrial RNA abundances (PubMed:10618642, PubMed:34789336, PubMed:37770567). Supplies pyrimidine ribonucleoside triphosphates (rNTPs) for mitochondrial transcription and is required for the maintenance of mitochondrial DNA (mtDNA) when the import of pyrimidine deoxyribonucleoside triphosphates (dNTPs) is limited from the cytosol is limited (PubMed:37439264). As a monomer, lacks nucleoside diphosphate kinase (NDPK) activity (PubMed:34789336). {ECO:0000269|PubMed:10618642, ECO:0000269|PubMed:34789336, ECO:0000269|PubMed:37439264, ECO:0000269|PubMed:37770567}.