Component of the nexin-dynein regulatory complex (N-DRC), a key regulator of ciliary/flagellar motility which maintains the alignment and integrity of the distal axoneme and regulates microtubule sliding in motile axonemes (PubMed:12847082, PubMed:23427265, PubMed:25411337). Plays an important role in the assembly of the N-DRC linker (PubMed:23427265). Component of the nexin-dynein regulatory complex (N-DRC), composed of at least DRC1, DRC2, DRC3, DRC4, DRC5, DRC6, DRC7, DRC8, DRC9, DRC10 and DRC11 (PubMed:25411337, PubMed:12847082, PubMed:23427265). Interacts with DRC1, DRC2 and DRC5 (PubMed:23427265). Defects in DRC4 give the pf2 phenotype characterized by disruption of the assembly of several other N-DRC subunits and an altered waveform that results in slow swimming cells. Belongs to the DRC4 family.