As component of a spoke-associated complex, regulates flagellar dynein activity by mediating regulatory signals between the radial spokes and dynein arms. Identified in a spoke-associated complex containing CFAP61, CFAP91 and CFAP251; the complex is associated with the radial spokes of the axoneme (PubMed:17967944). The complex associates with Calmodulin; the association is calcium sensitive (PubMed:17967944). Interacts with RSP3 (PubMed:17967944). Belongs to the CFAP91 family.