The Opsins: Lies Between Image Forming and Non-image Forming Process

Abstract

Light, the most abundant and important stimuli, can be sensed by a single photon by the photoreceptors. These photoreceptors are usually a group of protein of GPCR (G protein-coupled receptor) family. Opsins, a group of this family absorb these photons and processes both image forming and non-image forming phototransduction. Initially, their role was only limited to image formation, but recent studies reveal their importance in non -image forming functions also. In this review, we discussed various roles of opsins other than image formation, such as in photorelaxation of blood vessels, mechanoreception of skin, temperature regulation, hearing, immune system, thermotaxis of sperms, photosensation as well as in reproduction. These various functions of opsins show their immense importance in non-image forming functions as well as their evolutionary importance.