NM23-H2 or NME-2 (non-metastatic cell 2; also Nucleoside diphosphate kinase B, nm23-H2/B, NDPK-B and PUF) is a 17-19 kDa class 1 member of the NME/NDPK family of molecules. It is widely expressed, found in both cytosol and nucleus, and participates in multiple activities. In conjunction with nm23-H1, NME-2 forms homo- and heterohexamers (three dimers or two trimers) that mediate the transfer of phosphate from ATP to nucleoside diphosphates. It also serves as a transcriptional regulator of genes such as c-myc and PDGF-A. Human NME-2 is 152 amino acids (aa) in length. It contains a kinase region (aa 5-134), two potential phosphorylation sites (Tyr52 and Thr94), a phosphohistidine residue at position 118, and multiple lysine acetylation sites. There is one potential NME-2 splice form that shows a six aa substitution for aa 77-152. The genes for NME-1 and NME-2 are adjacent, and an unusual splicing event generates a 33 kDa fusion protein (NM23-LV) that is composed of aa 1-114 of NME-1 plus a Thr insert that is N-terminally coupled to full-length NME-2. Full-length human NME-2 shares 88% and 98% aa identity with human NME-1 and mouse NME-2, respectively.