PHOSPHORYLATION OF NM23 NUCLEOSIDE DIPHOSPHATE KINASE BY CASEIN KINASE-2 IN-VITRO/

We have investigated phosphorylation of human nucleoside diphosphate k inase (NDPK) and of homologous NDPK from different species by human ca sein kinase 2 (CK-2). The human NDPK isotypes A and B were phosphoryla ted by CK-2 in vitro both when the purified proteins and total lysate of HL-60 leukemia cells were used. The homologous NDPK's from Yeast an d E. coli were also substrates for CK-2 in vitro, but not Drosophila N DPK. Phosphorylation of all NDPK types by the CK-2 holoenzyme was enti rely polyamine-dependent. The CK-2 phosphorylation site in human NDPK A, that was about 2.5 times stronger phosphorylated than was the B iso type, was tentatively assigned to Ser-122. The location of the corresp onding residue in the 3D-structure of the 80% homologous Drosophila ND PK suggests that its phosphorylation may directly influence substrate binding and/or catalysis. (C) 1994 Academic Press, Inc.