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Pseudokinase domain of the membrane Guanylate Cyclase receptor, GC-C The pseudokinase domain shows similarity to protein kinases but lacks crucial residues for catalytic activity and/or ATP binding. GC-C binds and is activated by the intestinal hormones, guanylin (GN) and uroguanylin (UGN), which are secreted after salty meals to inhibit sodium absorption and induce the secretion of chloride, bicarbonate, and water. GN and UGN are also present in the kidney, where they induce increased salt and water secretion. This prevents the development of hypernatremia and hypervolemia after ingestion of high amounts of salt. Membrane (or particulate) GCs consist of an extracellular ligand-binding domain, a single transmembrane region, and an intracellular tail that contains a PK-like domain, an amphiphatic region and a catalytic GC domain that catalyzes the conversion of GTP into cGMP and pyrophosphate. Membrane GCs act as receptors that transduce an extracellular signal to the intracellular production of cGMP, which has been implicated in many processes including cell proliferation, phototransduction, and muscle contractility, through its downstream effectors such as PKG. The PK-like domain of GCs functions as a negative regulator of the catalytic GC domain and may also act as a docking site for interacting proteins such as GC-activating proteins. The GC-C subfamily is part of a larger superfamily that includes the catalytic domains of protein serine/threonine kinases, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",