Testis-specific serine/threonine-protein kinase required during spermatid development. Phosphorylates TSKS at 'Ser-288' and SPAG16. Involved in the late stages of spermatogenesis, during the reconstruction of the cytoplasm. During spermatogenesis, required for the transformation of a ring-shaped structure around the base of the flagellum originating from the chromatoid body. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Activated by phosphorylation on Thr-174, potentially by autophosphorylation. Interacts with TSSK1B. Interacts with HSP90; this interaction stabilizes TSSK2 (By similarity). Present in the cytoplasm of elongating spermatids. In spermatozoa, localizes in the equatorial segment, neck, the midpiece and in a specific sperm head compartment (By similarity). In spermatids, concentrates in centrioles during flagellogenesis. Testis-specific. Present in mature spermatozoa (at protein level). Autophosphorylated. Ubiquitinated; HSP90 activity negatively regulates ubiquitination and degradation. TSSK1B might be used as a target for male contraception or and intra-vaginal spermicides. Belongs to the protein kinase superfamily. CAMK Ser/Thr protein kinase family.