Opsins, the protein moieties of animal visual photo-pigments, have emerged as moonlighting proteins with diverse, light-dependent and -independent physiological functions. This raises the need to revise some basic assumptions concerning opsin expression, structure, classification, and evolution.
Keywords: G protein-coupled receptors; moonlighting proteins; photosensitivity; sensory cell evolution; sensory transduction; vision.
© The Author(s) 2022. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.