GUCA binds Ca2+ to form GUCA:Ca2+

Stable Identifier
Reaction [transition]
Homo sapiens
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The activity of guanylyl cyclases is regulated by Ca2+-binding, guanylyl cyclase-activating proteins (GCAPs). This regulation is the most important negative feedback mechanism triggered by Ca2+ in light. There are three GCAPs in humans; GUCA1A (Subbaraya et al. 1994), GUCA1B (Surguchov et al. 1997) and GUCA1C (Haeseleer et al. 1999). In darkness, when intracellular Ca2+ is relatively high, GCAPs suppress guanylate cyclase activity. But the light-induced fall in Ca2+ prompts Ca2+ to dissociate from GCAPs and be replaced by Mg2+, allowing the GCAPs to stimulate guanylate cyclase activity by an order of magnitude. Different GCAPs have different affinities for Ca2+. Defects in GCAP1 give rise to cone dystrophy and Lebers congenital amaurosis (
Literature References
PubMed ID Title Journal Year
9119368 The human GCAP1 and GCAP2 genes are arranged in a tail-to-tail array on the short arm of chromosome 6 (p21.1)

Knowles, JA, Surguchov, A, Banerjee, P, Subbaraya, I, Baehr, W, Bronson, JD, Ruiz, C, Palczewski, K

Genomics 1997
7983048 Molecular characterization of human and mouse photoreceptor guanylate cyclase-activating protein (GCAP) and chromosomal localization of the human gene.

Rao, PN, Gorczyca, WA, Subbaraya, I, Pettenati, MJ, Helekar, BS, Zhao, X, Baehr, W, Ruiz, CC, Palczewski, K

J Biol Chem 1995
10037746 Molecular characterization of a third member of the guanylyl cyclase-activating protein subfamily

Pettenati, M, Li, N, Bronson, D, Wechter, R, Rao, N, Baehr, W, Sokal, I, Haeseleer, F, Palczewski, K

J. Biol. Chem. 1999
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