Required for assembly of dynein regulatory complex (DRC) and inner dynein arm complexes, which are responsible for ciliary beat regulation, by acting as a molecular ruler that determines the 96 nanometer (nm) repeat length and arrangements of components in cilia and flagella (PubMed:25395538). Together with CCDC39/FAP59 forms a 96-nm-long complex in flagella. This complex does not act as a physical ruler, but rather act as a negative regulator for radial spokes: the complex lays along specific protofilaments, masking radial spoke binding sites and allowing recruitment of inner dynein arm (IDA) and nexin-dynein regulatory complexes (N-DRC) (PubMed:25395538). Interacts with CCDC39/FAP59. Asymmetrically dimethylated at Arg-246 and Arg-523 during flagellum resorption. Probably methylated by PRMT1. Short and immotile flagella. Inner dynein arm (IDA) and nexin-dynein regulatory complex (N-DRC) components are absent or severely reduced. Radial spokes are attached to doublet microtubules with an irregular periodicity of 32 nm instead of 96 nm. Belongs to the CCDC40 family. The length of things - Issue 170 of June 2015