May play a role in sperm motility, especially in the regulation of flagellar function. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Testis-specific. Expressed in the testis from 22 days postpartum (22 dpp). Tw12 allele. Encoded on the T-complex, a region of 20-30 Mb on proximal third of mouse chromosome 17. Naturally occurring variant forms of the T-complex, known as complete t-haplotypes, are found in wild mouse populations. The t-haplotypes contain at least four nonoverlapping inversions that suppress recombination with the wild-type chromosome, and lock into strong linkage disequilibrium loci affecting normal transmission of the chromosome, male gametogenesis and embryonic development. Belongs to the protein kinase superfamily. Tyr protein kinase family. Smok subfamily.