Cloning and expression of frog rhodopsin cDNA

The cDNA encoding the putative rhodopsin of frog (Rana catesbeiana) was cloned and expressed in cultured cells. The deduced amino acid sequence (354 residues) has more than 90% identity with the rhodopsins of two other frogs (Rana pipiens and Xenopus laevis) and 80% identity with other vertebrate rhodopsins. The isoelectric point calculated from the sequence was about 8.2, which is intermediate between rhodopsins and the cone visual pigments of higher vertebrates. The cloned cDNA was expressed in cultured mammalian cells. The difference absorbance maximum before and after photobleaching was about 500 nm, the same as that observed in the retina, demonstrating that the cloned cDNA does indeed encode functional rhodopsin.