Two-component kinase-like activity of nm23 correlates with its motility-suppressing activity.

Abstract

Nm23 genes, which encode nucleoside diphosphate kinases, have been implicated in suppressing tumor metastasis. The motility of human breast carcinoma cells can be suppressed by transfection with wild-type nm23-H1, but not by transfections with two nm23-H1 mutants, nm23-H1(S12OG) and nm23-H1(P96S). Here we report that nm23-H1 can transfer a phosphate from its catalytic histidine to aspartate or glutamate residues on 43-kDa membrane proteins. One of the 43-kDa membrane proteins was not phosphorylated by either nm23-H1(P96S) or nm23-H1(S120G), and another was phosphorylated much more slowly by nm23-H1(P96S) and by nm23-H1(S120G) than by wild-type nm23-H1. Nm23-H1 also can transfer phosphate from its catalytic histidine to histidines on ATP-citrate lyase and succinic thiokinase. The rates of phosphorylation of ATP-citrate lyase by nm23-H1(S120G) and nm23-H1(P96S) were similar to that by wild-type nm23-H1. The rate of phosphorylation of succinic thiokinase by nm23-H1(S120) was similar to that by wild-type nm23-H1, and the rate of phosphorylation of succinic thiokinase by nm23-H1(P96S) was about half that by wild-type nm23-H1. Thus, the transfer of phosphate from nm23-H1 to aspartates or glutamates on other proteins appears to correlate better with the suppression of motility than does the transfer to histidines.