dimerization/docking (D/D) domains found in the cAMP-dependent protein kinase regulatory subunit (PRKAR) and the DPY30/SDC1-like family; This hierarchy includes the dimerization/docking (D/D) domains of type I and type II cAMP-dependent protein kinase (PKA) regulatory (R) subunits, DPY30 from animals and its homologs, SDC1 from yeasts, and similar domains. PKA is a serine/threonine kinase (STK), catalyzing the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. The inactive PKA holoenzyme is a heterotetramer composed of two phosphorylated and active catalytic subunits with a dimer of R subunits. Activation is achieved through the binding of the important second messenger cAMP to the R subunits, which leads to the dissociation of PKA into the R dimer and two active subunits. There are two classes of R subunits, RI and RII; each exists as two isoforms (alpha and beta) from distinct genes. These functionally non-redundant R isoforms allow for specificity in PKA signaling. The R subunit contains an N-terminal D/D domain, a linker with an inhibitory sequence (IS), and two c-AMP binding domains. The D/D domain dimerizes to form a four-helix bundle that serves as a docking site for A-kinase-anchoring proteins (AKAPs), which facilitates the localization of PKA to specific sites in the cell. 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 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 (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. DPY30/SDC1 contains a C-terminal helical bundle domain that directly interacts with Ash2L (in human)/Bre2 (in yeast) COMPASS through the DPY30-binding motif (DBM). The DPY30/SDC1 helical bundle domain, also called D/D domain, is formed of two alpha-helices that may be analogous to the D/D domain found in regulatory subunit of PKA.

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gi 902967458  22 TYMEDAVCQLLENREDisqyGIARFFTDYFNSV 54
Cdd:cd22957    1 ELLQDAVAKLLEERPE----DPVEFLAEYFEKA 29