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

摘要

>We have identified a cDNA encoding a 212 amino acid protein (Nm23-H5) with 27–31% identity to the human members of the nm23ucleoside 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 COOH-terminus 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.