Testis-specific serine/threonine-protein kinase required during spermatid development. Phosphorylates 'Ser-288' of TSKS. 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] Kinase activity is specifically inhibited by 2 classes of compounds: biphenyl compounds (1,1'-(biphenyl-4,4'-diyl)bis(2,2-dihydroxyethanone)) and 1,2,7-trialky-1H-imidazo[4,5-g]quinoxalin-6-one. Activated by phosphorylation on Thr-174 and potentially by autophosphorylation. Interacts with TSSK2. Interacts with HSP90; this interaction stabilizes TSSK1 (By similarity). In spermatozoa, present in the sperm head and in the flagellum. Testis-specific. Present in sperm (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.