Figure 4.

Spectral comparison of Rh7, parapinopsin, and Opn5m. (A) Spectral changes from all-trans- to 11-cis-retinal bound forms of lamprey parapinopsin (curve 1), chicken Opn5m (curve 2) and Drosophila Rh7-Cap (curve 3). Spectra were normalized to be ~1.0 at the negative maximum. (B) The calculated absorption spectra of three UV light-sensitive opsins (11-cis-retinal bound forms, curves 1–3) and their active states (all-trans-retinal bound forms, curves 4–6). Difference spectra of parapinopsin and Opn5m (curves 1 and 2 of (A)) were fitted with a template spectrum of bovine rhodopsin meta-I modeled by the Lamb and Govardovskii method^{22, 23} to calculate absorption spectra of all-trans-retinal bound forms (curves 4 and 5, respectively). Difference spectrum of Rh7 (curve 3 of (A)) was fitted with a template spectrum of squid retinochrome modeled by the Lamb and Govardovskii method to calculate the absorption spectrum of the all-trans-retinal bound form (curve 6). It should be noted that we calculated absorption spectra of three pigments by using the spectrum of squid retinochrome as a template; however, the base lines of spectra were not steady except for that of Rh7 (Fig. S3). Spectra of 11-cis-retinal bound forms of parapinopsin, Opn5m and Rh7 were determined by subtracting the difference spectra in (A) from the calculated spectra of all-trans-retinal bound forms (curves 1, 2 and 3, respectively).