Dimerization/Docking domain of Cyclic GMP-dependent Protein Kinase I alpha
Cyclic GMP-dependent Protein Kinase I (PKG1 or cGKI) is a Serine/Threonine Kinase (STK), catalyzing the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. cGKI exists as two splice variants, cGKI-alpha and cGKI-beta. They contain an N-terminal regulatory domain containing a dimerization/docking region and an autoinhibitory pseudosubstrate region, two cGMP-binding domains, and a C-terminal catalytic domain. Binding of cGMP to both binding sites releases the inhibition of the catalytic center by the pseudosubstrate region, allowing autophosphorylation and activation of the kinase. cGKI is a soluble protein expressed in all smooth muscles, platelets, cerebellum, and kidney. It is involved in the regulation of smooth muscle tone, smooth cell proliferation, and platelet activation. The dimerization/docking (D/D) domain is a leucine/isoleucine zipper that mediates both homodimerization and interaction with isotype-specific G-kinase-anchoring proteins (GKAPs). The D/D domain of the two variants (alpha and beta) differ, allowing for their targeting to different subcellular compartments and intracellular substrates. cGKI-alpha specifically binds to myosin light chain phosphatase targeting subunit (MYPT1) and the regulator of G-protein signaling-2 (RGS-2). cGKI-alpha activates the phosphatase activity of MYPT1, resulting in vasorelaxation. It increases the activity of RGS-2 toward G proteins, with implications in the downstream signaling for vasoconstrictive agents.
Jiyao W et al.(2023). "The conserved domain database in 2023.",