Iodopsin

iodopsin or iodopsin is a chromoprotein, a pigment located in the outer segments of the cones of the human eye, and is responsible for color perception. This has a higher concentration in the fovea. It is associated with vitamin A. Upon receiving light, it produces a potential difference that gives rise to an electrical current through which visual information is transmitted through neurons to the brain. Iodopsins are covalently bound photopsins (ie proteins), each with a type 1 coloring substance (chromophore): neoretinin (11-cis-retinol) or retinal (11-cis-retinal). Pigments whose protein component photopsin binds to a type 2 chromophore (3,4-dehydro-11-cis-retinal) are not known as iodopsin, but as porphyropsin. The absorption maxima and photopsins of the three human iodopsins are:

• 560 nm: Red-sensitive L-yodopsin with L-photopine, UniProt P04000. Defects in the OPN1LW gene are the cause of protanopia
• 530 nm: M-yodopsin green sensitive with M-photopine, UniProt P04001. Defects in the OPN1MW gene are the cause of deuteranopia
• 420 nm: S-yodopsin sensitive to blue with S-photopine, UniProt P03999. Defects in the OPN1SW gene are the cause of tritanopia

In the animal kingdom, in addition to these visual pigments with Retinal 1 as a chromophore,

340 nm: UV-sensitive UV iodopsin with UV photopsin and 620 nm: infrared sensitive XL-iodopsin with XL-photopsin before.

Iodopsins contain 350 to 360 amino acids and are membrane proteins that belong to G protein-coupled receptors.