dimerization/docking (D/D) domain found in Chlamydomonas reinhardtii flagellar radial spoke protein 4 (RSP4) and similar proteins
Flagellar radial spokes contribute to the regulation of dynein arm activity and thus the pattern of flagellar bending. They consist of a thin stalk, which is attached to a subfiber of the outer doublet microtubule, and a bulbous head, which is attached to the stalk and appears to interact with the projections from the central pair of microtubules. The radial spoke head is made of five different polypeptides (RSP1, RSP4, RSP6, RSP9, and RSP10). This family includes the radial spoke head proteins RSP4 and RSP6 from Chlamydomonas reinhardtii, and several eukaryotic homologs, including mammalian RSHL1 (also called RSPH6A) and RSHL3 (also called RSPH4A), the protein products of familial ciliary dyskinesia candidate genes. RSHL1 is essential for sperm flagellar assembly and male fertility. RSHL3 is a component of the axonemal radial spoke head which plays an important role in ciliary motility. It is required for triplet radial spokes (RS1, RS2 and RS3) head assembly in the motile cilia. Members of this family contain an N-terminal domain which shows high sequence similarity to the dimerization/docking (D/D) domains of regulatory subunit of cAMP-dependent protein kinase (PKA) and protein DPY-30/SDC1.
Jiyao W et al.(2023). "The conserved domain database in 2023.",