IDENTIFICATION AND CHARACTERIZATION OF A NOVEL PROTEIN-KINASE, TESK1,SPECIFICALLY EXPRESSED IN TESTICULAR GERM-CELLS

We have isolated cDNA clones encoding the rat and human forms of a nov el protein kinase, termed TESK1 (testis-specific protein kinase 1), Se quence analysis indicates that rat TESK1 contains 628 amino acid resid ues, composed of an N-terminal protein kinase consensus sequence follo wed by a C-terminal proline-rich region, Human TESK1 contains 626 amin o acids, sharing 92% amino acid identity with its rat counterpart, The protein kinase domain of TESK1 is structurally similar to those of LI MK (LIM motif-containing protein kinase)-1 and LIMK2, with 49-50% sequ ence identity, Phylogenetic analysis of the protein kinase domains rev ealed that TESK1 is most closely related to a LIMK subfamily, Chromoso mal localization of human TESK1 gene was assigned to 9q13, Anti-TESK1 antibody raised against the C-terminal peptide of TESK1 recognized two polypeptides of 68 and 80 kDa in cell lysates of COS cells transfecte d with human TESK1 cDNA expression plasmid, TESK1 protein expressed in COS cells exhibited serine/threonine kinase activity, when myelin bas ic protein was used as a substrate, Northern blot analysis revealed th at TESK1 mRNA was specifically expressed in rat and mouse testicular g erm cells, The TESK1 mRNA in the testis was detectable only after the 18th day of postnatal development of mice and was mainly expressed in the round spermatids. These observations suggest that TESK1 has a spec ific function in spermatogenesis.