Serine/threonine-protein kinase component of the sperm flagellar doublet microtubules (PubMed:15870294). May act as a regulator of sperm motility by mediating phosphorylation of sperm doublet microtubule proteins (By similarity). Plays a role in DNA condensation during postmeiotic chromatin remodeling and histone-to- protamine transition during spermatogenesis (By similarity). . This is the function of ENSG00000178093 (TSSK6, testis specific serine kinase 6).