dimerization/docking (D/D) domain found in the DPY30/SDC1-like family
The DPY30/SDC1-like family includes DPY30 from animals and its homolog SDC1 from yeast, DPY30 domain-containing protein (DYDC), adenylate kinase 7 (AK7), IQ domain-containing protein K (IQCK), nucleoside diphosphate kinase homolog 5 (NDKH5), EF-hand calcium-binding domain-containing protein 5 (EFCAB5), and Chlamydomonas reinhardtii flagellar radial spoke proteins, RSP2 and RSP23. DPY30, also called dumpy-30, was initially discovered in Caenorhabditis elegans as a key player in X chromosome dosage compensation. Human DPY30 plays a dual function in moderately allosterically regulating the methyltransferase activity of SET1/COMPASS (COMplex of Proteins ASsociated with Set1) enzymes and contributing to the recruitment of the complex to chromatin. Yeast SDC1, also called complex proteins associated with SET1 protein SDC1, Set1C component SDC1, or suppressor of CDC25 protein 1, is the smallest subunit of COMPASS (COMplex of Proteins ASsociated with Set1) and interacts exclusively with Bre2 at the distal end of the catalytic module. It positively regulates the COMPASS catalytic module by stabilizing the non-canonical Bre2 SPRY domain. DYDC1 plays a crucial role during acrosome biogenesis. AK7 (EC2.7.4.3/EC 2.7.4.6), also called ATP-AMP transphosphorylase 7, is a nucleoside monophosphate (NMP) kinase that catalyzes the reversible transfer of the terminal phosphate group between nucleoside triphosphates and monophosphates. It is involved in maintaining ciliary structure and function. IQ motif-containing proteins may play an active role in cell polarization and migration, and even in ciliary function. The function of IQCK remains unclear. NDKH5, also called NME5, NDP kinase homolog 5, inhibitor of p53-induced apoptosis-beta (IPIA-beta), testis-specific nm23 homolog, or nm23-H5, is specifically expressed in testis germinal cells. It may not have NDK kinase activity. It confers protection from cell death by Bax and alters the cellular levels of several antioxidant enzymes including Gpx5. It may play a role in spermiogenesis by increasing the ability of late-stage spermatids to eliminate reactive oxygen species. RSP2 is a calmodulin binding spoke stalk protein required for motility in Chlamydomonas reinhardtii. It binds calmodulin in a calcium-dependent manner. RSP23, also called p61, is a functional Ca2+/calmodulin-regulated nucleoside diphosphate kinase (NDK) from the flagella of Chlamydomonas that is present in the radial spoke stalk. It binds calmodulin in a calcium-dependent manner. Members of this family contain a DPY30/SDC1 helical bundle domain that is formed by two alpha-helices. The DPY30/SDC1 helical bundle domain is also called D/D domain and might be analogous to the D/D domain found in the regulatory subunit of cAMP-dependent protein kinase (PKA).
Jiyao W et al.(2023). "The conserved domain database in 2023.",