Involved in sperm flagellum axonemal organization and function (By similarity). May regulate cilium motility through its role in the assembly of the axonemal radial spokes (By similarity). Part of a complex containing MYCBP, AKAP1 and PRKAR2B. Expressed in the testis, in cells involved in spermatogenesis. Expression begins in 1 week old mice. Phosphorylated by PKA. Belongs to the CFAP91 family.