Characterisation of the ultraviolet-sensitive opsin gene in the honey bee, Apis mellifera

The cDNA sequence of the ultraviolet-sensitive opsin in the honey-bee, Apis mellifera, with associated 5' and 3' untranslated regions, is presented. The analysis of genomic structure reveals seven introns in the coding region of the gene, with six at novel positions for an insect opsin gene. The equivalent site to the counterion in vertebrate opsins is occupied by a Tyr residue. This contrasts with the presence of Phe at this site in the ultraviolet-sensitive opsins of Drosophila sps. A comparison of the amino acid sequence within the seven a-helical transmembrane regions of insect ultraviolet/blue-sensitive opsins identifies substitution at five sites that involve either replacement of a polar with a non-polar residue, or a change in charge. Such changes an known to result in spectral shifts in vertebrate pigments. Phylogenetic analysis indicates that the ultraviolet-sensitive pigments represent an ancient class of insect opsins.