dimerization/docking (D/D) domain found in Saccharomyces cerevisiae cAMP-dependent protein kinase regulatory subunit and similar domains
cAMP-dependent protein kinase (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 regulatory (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. The R subunit of fungal PKA is encoded by a single gene, which is called by various names in different organisms (for example: Yarrowia lipolytica RKA1, Saccharomyces cerevisiae Bcy1, and Schizosaccharomyces pombe Cgs1). Although most characterized PKA holoenzymes are tetramers, Y. lipolytica PKA has been reported to be a dimer of RKA1 and the catalytic subunit TPK1. RKA1 is essential and promotes hyphal growth. Cgs1 is essential for sexual differentiation of S. pombe; mutants with defective Cgs1 are partially sterile. The R subunit contains an N-terminal dimerization/docking (D/D) domain, a linker with an inhibitory sequence, and two c-AMP binding domains. The D/D domain of metazoan R subunits dimerizes to form a four-helix bundle that serves as a docking site for A-kinase-anchoring proteins (AKAPs). The D/D domain of fungal R subunits may also serve as a dimerization domain, in the case of heterotetrameric PKAs. Fungal PKA plays a major role in controlling cell growth and metabolism in response to nutrients and stress conditions.
Jiyao W et al.(2023). "The conserved domain database in 2023.",