Rhodopsin is a light-sensitive G protein-coupled receptor (GPCR) located in the rod photoreceptor cells of the retina.
It is composed of the apoprotein opsin, which is covalently bound to the chromophore 11-cis-retinal, a derivative of vitamin A.
When a photon is absorbed, 11-cis-retinal undergoes isomerization to all-trans-retinal, prompting a conformational change in rhodopsin.
This change activates the G protein transducin, initiating the phototransduction cascade necessary for vision in low-light conditions.
Rhodopsin remains highly stable in the dark and efficiently converts light into a biochemical signal, with photon absorption leading to downstream signaling activation within milliseconds.
Mutations in the gene encoding rhodopsin (RHO) can result in retinal degenerative diseases such as retinitis pigmentosa, highlighting its critical role in maintaining retinal health and visual function.