intracellular stimulation of guanylate cyclase (GC) by calcium, a key event in the recovery of the dark state of rod photoreceptors after exposure to light, is mediated by guanylate cyclase-activating protein (GCAP1). GCAPs are calcium-The binding proteins belonging to the calmodulin superfamily. GCAP1 is a calcium-binding protein that stimulates synthesis of c-GMP in photoreceptors. GCAP1 is present in rod and cone photoreceptor outer segments where phototransduction occurs. In contrast to other calcium-binding proteins from the calmodulin superfamily, the calcium-free form of GCAP1 stimulates the effector enzyme. By molecular cloning of human and mouse GCAP cDNA, the known mammalian GCAPs are found to be more than 90 % similar, consisting of 201 to 205 amino acids, and containing three identically conserved calcium-binding sites. A related protein, GCAP2, is detectable only in the retina and results from a gene duplication event.
Synonyms: COD3, GCAP 1, GCAP, Guanylate Cyclase Activating Protein Photoreceptor 1, Guanylate Cyclase Activating Protein Photoreceptor 1, Guanylate Cyclase Activator 1A, Guanylate Cyclase Activator 1A, Guanylin 1, Guanylin 1, guanylyl cyclase activating protein 1, Guanylyl cyclase-activating protein 1, GUC1A_HUMAN, GUCA, GUCA1, GUCA1A, GUCA1A.