Rhodopsin 7–The unusual Rhodopsin inDrosophila

Abstract

Rhodopsins are the major photopigments in the fruit flyDrosophila melanogaster. Drosophilaexpress six well-characterized Rhodopsins (Rh1–Rh6) with distinct absorption maxima and expression pattern. In 2000, when theDrosophilagenome was published, a novelRhodopsingene was discovered:Rhodopsin 7(Rh7).Rh7is highly conserved among theDrosophilagenus and is also found in other arthropods. Phylogenetic trees based on protein sequences suggest that the sevenDrosophilaRhodopsins cluster in three different groups. While Rh1, Rh2 and Rh6 form a “vertebrate-melanopsin-type”–cluster, and Rh3, Rh4 and Rh5 form an “insect-type”-Rhodopsin cluster, Rh7 seem to form its own cluster. Although Rh7 has nearly all important features of a functional Rhodopsin, it differs from other Rhodopsins in its genomic and structural properties, suggesting it might have an overall different role than other known Rhodopsins.