Testis Specific Serine Kinase 2 (TSSK2)

Using mouse Tssk2 to search a database, followed by PCR of a testis cDNA library, Hao et al. (2004) cloned human TSSK2. The deduced 358-amino acid protein contains the 12 subdomains characteristic of serine/threonine kinases. TSSK2 and TSSK1 share 72% amino acid identity overall and 83% identity in the kinase region.

Northern blot analysis of human tissues detected a 1.7-kb TSSK2 transcript in testis only. Real-time PCR revealed abundant TSSK2 expression in testis and lower levels in heart, brain, and placenta. Western blot detected TSSK2 at the predicted molecular mass of 40 kD in human sperm and testis. Immunohistochemical analysis localized TSSK2 to the sperm head, with intense staining in the equatorial segment.