FIGURE 1.

Effect of 11-cis-retinol and -retinal on opsin activation and pigment regeneration in salamander red rods. A, transducin activation by expressed salamander red rod opsin (open circles), with 11-cis-retinol (filled circles) and with 11-cis-retinal (triangles). Each sample was assayed in triplicate and averaged; error bars reflect mean ± S.E. and often were smaller than the symbol size. At 5.5 min, samples with 11-cis-retinal and 11-cis-retinol were illuminated with light for 12 s as described under “Experimental Procedures” and illustrated in the figure with the vertical line. B, absorption spectra of isolated salamander red rods measured microspectrophotometrically in native state (gray circles, n = 28), measured ∼130 min following a complete (>90%) bleach (black filled circles, n = 3), measured 130–190 min after treatment with 11-cis-retinol following a complete bleach (open circles, n = 4), and measured 140–200 min after treatment with 11-cis-retinal following a complete bleach (triangles, n = 9). Retinoids were suspended in lipid vesicles or ethanolic solution. Continuous curves fitted to the data are sums of templates for A1 and/or A2 visual pigments (see “Experimental Procedures”).