Figure 6.

Removal of all-trans-retinol by IRBP in purified bovine ROS membranes. Rhodopsin (spectrum 0, concentration 10 μm) in purified ROS membranes was bleached for 5 min with >495 nm light in the presence of different concentrations of IRBP (0, 2, and 5 μm) and with or without NADPH (100 μm). After 30 min at 37 °C, in the presence of NADPH the released all-trans-retinal had been quantitatively converted to all-trans-retinol (spectra 1–3), whereas in the absence of NADPH it remained unconverted (spectra 4–6). In the absence of IRBP, both all-trans-retinol and all-trans-retinal remained in the membranes (spectra 1 and 4). 2 μm (spectrum 2) and 5 μm (spectrum 3) IRBP removed all-trans-retinol but had no effect on all-trans-retinal (spectra 5 and 6). To obtain the spectra, ROS membranes were solubilized in 1% Ammonyx LO at the end of incubation.