Characterization of nucleosidediphosphate (NDP)-kinase-associated GTP binding proteins from human recombinant interleukin 2 (rIL-2)-treated mouse NK cells

Abstract

Nucleosidediphosphate (NDP)-kinase-associated proteins from rIL-2-treated mouse NK cells have been biochemically characterized. The associated proteins could be separated from partially purified NDP-kinases by the 5-25% glycerol density gradient centrifugation method after treatment with 6 M urea in the presence of 1 mM EDTA. The associated proteins (approx. Mr 20,000) were defined as GTP binding proteins, since only [alpha-32P]GTP was bound to these proteins in the presence of 5 mM Mg2+ at 37 degrees C. We also found that these GTP binding proteins hydrolyzed only GTP in the presence of 5 mM Mg2+. The data presented here for: GTP specific binding activity; GTPase activity; and molecular size (approx. Mr 20,000) of the NDP-kinase-associated GTP binding proteins are similar to those reported for ras oncogene products (p21 proteins).