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(biochemistry) Any of a group of light-sensitive proteins in the retina.

Three-dimensional structure of cattle rhodopsin. The seven transmembrane domains are shown in varying colors. The chromophore is shown in red.

(biochemistry) Any of a group of light-sensitive proteins in the retina.

The retinal molecule inside an opsin protein absorbs a photon of light. Absorption of the photon causes retinal to change from its 11-cis-retinal isomer into its all-trans-retinal isomer. This change in shape of retinal pushes against the outer opsin protein to begin a signal cascade, which may eventually result in chemical signaling being sent to the brain as visual perception. The retinal is re-loaded by the body so that signaling can happen again.

(biochemistry) Any of a group of light-sensitive proteins in the retina.

Most known opsins have the retinal binding lysine except some among the tetraopins, The outgroup contains other G protein-coupled receptors.