Functional characterization of visual and nonvisual pigments of American chameleon (Anolis carolinensis)

Using only 11-cis 3, 4-dehydroretinal as a chromophore in the pure-cone retina, American chameleon (Anolis carolinensis) detects a wide range of color from ultraviolet (UV) to infrared. We previously characterized its visual opsin genes sws1Ac, sws2Ac, rh1Ac, rh2Ac, and LwsAc that encode SWS1Ac, SWS2Ac, RH1Ac, RH2Ac, and LWSAc opsins, respectively, and the pineal gland-specific opsin (PAc) gene. Here we present the light absorption profiles of the visual pigments obtained by expressing these opsins and reconstituting them with 11-cis retinal using the COS1 cell cDNA expression system. The purified SWS1Ac, SWS2Ac, RH1Ac, RH2Ac, LWSAc, and PAc pigments have the wavelengths of maximal absorption at 358, 437, 491, 495, 560, and 482 nm, respectively. SWS1Ac is the first vertebrate UV opsin whose spectral sensitivity has been directly evaluated. RH1 pigments, orthologous to the rod pigments of other vertebrates, are sensitive to hydroxylamine in the dark, exhibiting a cone pigment-like characteristic, probably reflecting their adaptation to the pure cone retina. Interestingly, the blue-sensitive SWS2Ac pigment shows an exceptionally low level of sensitivity to hydroxylamine, possessing a rod pigment-like characteristic.