Chromatography on immobilized antibodies specific to nucleoside diphosphate (NDP) kinase was utilized for affinity purification of this enzyme from detergent extracts of frog heart post-mitochondrial fractions. SDSpolyacrylamide gel electrophoresis analysis of eluates from these supports shows that five polypeptides copurify with nucleoside diphosphate (NDP) kinase. Tryptic digests of each band were analyzed by mass spectrometric microsequencing. Data base searches by peptide mass matching and sequence homology led to the identification of these proteins as glyceraldehyde-3-phosphate dehydrogenase (40 kDa), creatine kinase (45 kDa), vimentin (55 kDa), pyruvate kinase (60 kDa), and a putative member of the antioxidant protein family (28 kDa). Distinct protein compositions were found in eluates of lung and liver extracts processed in a like manner. The 28-kDa band and vimentin were associated with NDP kinase from all tissues, but co-purification of pyruvate kinase was seen only in liver, while creatine kinase and glyceraldehyde-3-phosphate dehydrogenase were absent from eluates from lung and liver. The results suggest that while NDP kinase is associated with vimentin intermediate filaments and an antioxidant protein in most tissues, it interacts with energy metabolism enzymes in a tissue-specific manner.In recent years NDP kinase 1 has been found to have unexpected roles, in addition to its well known ability to catalyze transfer of phosphate groups from trinucleotides to dinucleotides (1). NDP kinases are involved in growth, differentiation, development, tumor progression, metastasis, and apoptosis (reviewed in Ref. 2). NDP kinase participates in muscarinic K ϩ channel opening (3), is a transcription factor for c-myc (4) and a protein kinase as well (5, 6). These varied functions seem to be accomplished by a limited number of gene products: to date, complete cDNAs encoding 4 human NDP kinases (nm23-H1, nm23-H2, DR-nm23, and nm23-H4) have been identified (7-9).Also, in Dictyostelium a separate nuclear gene encodes a mitochondrial NDP kinase (10). Although other NDP kinase genes may be identified in the future, it is unlikely that each of the multiple functions associated with this protein is performed by a distinct isoform. Differential distribution of NDP kinase isoforms (11) may account for adaptation to the requirements of specific cell types. Additionally, interaction of distinct isoforms with cell-specific factors, conceivably other proteins, could govern NDP kinase function in different tissues. This in turn might explain apparently contradictory findings regarding the connection between NDP kinase and cancer (2): while in some cell types, studies of NDP kinase expression suggest that it has a metastasis suppressor function, in other systems this relation between expression of NDP kinase and metastatic potential is either nonexistent or operates in the opposite direction.The objective of the present work was to identify proteins that interact with NDP kinase in cardiac muscle. Immobilized antibodies to frog ...