Intrinsic nucleoside diphosphate kinase-like activity as a novel function of 14-3-3 proteins

14-3-3 proteins play a role in many cellular functions as molecular chaperone and adapter proteins: they bind to and modulate several proteins involved in cell proliferation and differentiation, and also function ATP-dependently in targeting of precursors to mitochondria. We show here that 14-3-3 purified from a human lymphoblastoma and also its recombinant τ isoform exhibited intrinsic nucleoside diphosphate (NDP) kinase-like activity. 14-3-3 proteins preferentially catalyzed the transfer of the γ-phosphate group from ATP, dATP or dGTP to all nucleoside diphosphates and this transfer involved acid-labile phosphoenzyme intermediates. They also simultaneously catalyzed the reverse reaction of ATP hydrolysis. These properties of 14-3-3 are similar to those of NDP kinase, but not to those of adenylate kinase.