Stable Identifier
Homo sapiens
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Opsins are light-sensitive, 35-55 kDa membrane-bound G protein-coupled receptors of the retinylidene protein family found in photoreceptor cells of the retina. Five classical groups of opsins are involved in vision, mediating the conversion of a photon of light into an electrochemical signal, the first step in the visual transduction cascade (Terakita A, 2005; Nickle B and Robinson PR, 2007). Another opsin found in the mammalian retina, melanopsin, is involved in circadian rhythms and pupillary reflex but not in image-forming (Hankins MW et al, 2008; Kumbalasiri T and Provencio I, 2005). Guanine nucleotide-binding proteins (G proteins) are involved as modulators or transducers in various transmembrane signaling systems. The G protein transducin, encoded by GNAT genes, is one of the transducers of a visual impulse that performs the coupling between rhodopsin and cGMP-phosphodiesterase. Defects in GNAT1 are the cause of congenital stationary night blindness autosomal dominant type 3, also known as congenital stationary night blindness Nougaret type. Congenital stationary night blindness is a non-progressive retinal disorder characterized by impaired night vision (Dryja TP et al, 1996). Defects in GNAT2 are the cause of achromatopsia type 4 (ACHM4). Achromatopsia is an autosomal recessively inherited visual disorder that is present from birth and that features the absence of color discrimination (Kohl S et al, 2002).
Literature References
PubMed ID Title Journal Year
16005867 Melanopsin and other novel mammalian opsins

Provencio, I, Kumbalasiri, T

Exp Eye Res 2005
8673138 Missense mutation in the gene encoding the alpha subunit of rod transducin in the Nougaret form of congenital stationary night blindness

Hahn, LB, Reboul, T, Arnaud, B, Dryja, TP

Nat Genet 1996
15774036 The opsins

Terakita, A

Genome Biol 2005
12077706 Mutations in the cone photoreceptor G-protein alpha-subunit gene GNAT2 in patients with achromatopsia

Kohl, S, VadalĂ , M, Lorenz, B, Rosenberg, T, Wissinger, B, Jacobson, SG, Kellner, U, Baumann, B

Am J Hum Genet 2002
18054803 Melanopsin: an exciting photopigment

Peirson, SN, Hankins, MW, Foster, RG

Trends Neurosci 2008
17726575 The opsins of the vertebrate retina: insights from structural, biochemical, and evolutionary studies

Robinson, PR, Nickle, B

Cell Mol Life Sci 2007
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