A new human nm23 homologue (nm23‐H5) specifically expressed in testis germinal cells¹

Abstract

We have identified a cDNA encoding a 212 amino acid protein (Nm23-H5) with 27^31% identity to the human members of the nm23/nucleoside diphosphate (NDP) kinase gene family. The nm23-H5 gene is located on chromosome 5q23^31 and is transcribed as one main transcript of 1.1 kb which is highly and specifically expressed in testis, in the spermatogonia and early spermatocytes. Nm23-H5 possesses most of the residues conserved among NDP kinases plus an additional COOHterminus end of 55 amino acids unique to this protein. However, under usual assay conditions, Nm23-H5 expressed in Escherichia coli did not exhibit NDP kinase activity. These results suggest that Nm23-H5 is specifically involved in early stages of spermatogenesis.z 1998 Federation of European Biochemical Societies.

Characterization of Human Thioredoxin-like 2

“…Txl-2 expressed in bacteria is inactive in both the thioredoxin assay and the autophosphorylation assay. A similar situation was found for the closest Txl-2 homolog, Sptrx-2, as well as other thioredoxins and NDP kinases (12,14,20). Taken together, the lack of enzymatic activity of bacterially produced Txl-2, despite its interaction with thioredoxin reductase, indicates that posttranslational modifications that might expose the active site upon conformational changes as well as interaction with other proteins or additional cofactors (cell-or tissue-specific) might be required for Txl-2 to function.…”

“…Group II encompasses nm23-H5 to H8 genes, which are defined by a more divergent sequence, including a sequence of the active site which is not strictly conserved. Furthermore, nm23-H5, H7, and H8 have been shown to have a tissue-specific distribution mainly in testis/spermatozoa (14,20,21).…”

12-O-Tetradecanoylphorbol-13-acetate and UV Radiation-induced Nucleoside Diphosphate Protein Kinase B Mediates Neoplastic Transformation of Epidermal Cells

“…DR-nm23 (nm23-H3), located on chromosome 16, is 70% identical to nm23-H1 and nm23-H2 and may play a role in normal hematopoiesis and in the induction of apoptosis (19). nm23-H5 was specifically expressed in testis and found to encode a protein devoid of NDP kinase activity (36). Nm23-H6 is a mitochondrial NDPK and affects cytokinesis (37).…”

Elevated plasma level of differentiation inhibitory factor nm23-H1 protein correlates with risk factors for myelodysplastic syndrome

“…[10][11][12][13][14][15][16] The nm23 proteins are involved in tumor metastasis regulation and have nucleoside diphosphate kinase enzyme activity that catalyzes the ATP-dependent synthesis of nucleoside diphosphates. [17][18][19][20][21][22][23][24] The expression of nm23-H1 has been reported to have an inverse relationship with metastatic potential and in various malignancies. 18 The inhibition of differentiation may be associated with the aggressive behavior of leukemia.…”