Rhodopsin
Rhodopsin is the photoreceptor protein in rod cells of vertebrate retina [1]. It is also known as opsin 2.
Rhodopsin is a member of the GPCR family, which is coupled to the G-protein, transducin. Rhodopsin, unlike many other GPCRs is activated by a photon of light not by the binding of a ligand. Infact, the ligand (11-cis retinal) is already bound in its inactive state. The photon causes a conformational change in the GPCR which causes activation of the transducin, whose α subunit, then activates cyclic GMP phosphodiesterase [2].
There are three mutations in the rhodopsin genes, two of which are transition mutations occuring at seperate nucleotides of codon 347 and one transversion mutation occuring at codon 58. The two transition mutations involve C changing to T. The transversion mutation involves C changing to G [3].
"Retinitis Pigmentosa" is an inherited disease that causes blindness or stationary night blindness, by degenerating retina cells. It might be an autosomal dominant or recessive and X-linked recessive disease, at which a mutation in the gene encoding rhodopsin. Vitamin A improves the condition [4][5].
References
- ↑ Hargrave P.A., McDowell J.H.(1992) Rhodopsin and phototransduction: a model system for G protein-linked receptors. The FASEB Journal, 6(6), 2323-2331
- ↑ Alberts.B, Johnson.A, Lewis.J, Raff.M, Roberts.K, Walter.P, 2008, Molecular Biology of the Cell, 5th Edition, New York, Garland Science
- ↑ Dryja TP et al (1990) Mutations within the rhodopsin gene in patients with autosomal dominant retinitis pigmentosa. N Engl J Med. 1990 Nov 8;323(19):1302-7.
- ↑ Kelly, J, (2011) Retinitis Pigmentosa 4; RP4,OMIM.org (lasst isited 20/11/2011)
- ↑ Thaddeus P. Dryja, M.D., Terri L. McGee, B.A., Lauri B. Hahn, M.S., et al. Mutations within the rhodopsin gene in patients with autosomal dominant retinitis pigmentosa. N Engl J Med 1990; 323:1302-1307.