and cone opsin families differ in spectral tuning domains but not signal transducing domains as judged by saturated evolutionary trace analysis

Abstract. The visual receptor of rods and cones is a covalent complex of the apoprotein, opsin, and the light-sensitive chromophore, 11-cis-retinal. This pig-ment must fulfill many functions including photoac-tivation, spectral tuning, signal transmission, inactivation, and chromophore regeneration. Rod and cone photoreceptors employ distinct families of opsins. Although it is well known that these opsin families provide unique ranges in spectral sensitivity, it is unclear whether the families have additional functional differences. In this study, we use evolu-tionary trace (ET) analysis of 188 vertebrate opsin sequences to identify functionally important sites in each opsin family. We demonstrate the following re-sults. (1) The available vertebrate opsin sequence