Necessary for sperm flagellar function. Plays a role in motile ciliogenesis. May help to recruit STK36 to the cilium or apical surface of the cell to initiate subsequent steps of construction of the central pair apparatus of motile cilia. Interacts with SPAG6 and STK36. Detected on the sperm flagellum. Detected in the central apparatus of the axoneme. Colocalizes with SPAG6 on microtubules. Expressed in testis. Phosphorylated by TSSK2.