Required for sperm production and function. Plays a role in DNA condensation during postmeiotic chromatin remodeling. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Mg(2+) and Mn(2+) were both present in the kinase buffer but Mg(2+) is likely to be the in vivo cofactor. Interacts with HSP90; this interaction stabilizes and activates TSSK6 (PubMed:23599433). Interacts with the heat shock proteins HSPCB, HSPA8 and HSPA1A. These interactions appear to be required for TSSK6 kinase activity. Interacts with TSACC; this interaction is direct and recruits TSACC to HSP90, which is essential for kinase activity (By similarity). Expressed in the testis, localized to the heads of elongating spermatids. Autophosphorylated. Ubiquitinated; HSP90 activity negatively regulates ubiquitination and degradation. Mice are sterile due to profound impairment in motility and morphology of spermatozoa. Belongs to the protein kinase superfamily. CAMK Ser/Thr protein kinase family.