Time course of spectral changes during rhodopsin decay and regeneration at pH 7.5 and 33 °C without NADPH (A), with 70 μm NADPH (B), and with both Gtα -HAA-peptide (100 μm) and NADPH (70 μm) (C). Disk membranes (4.3 μm rhodopsin) were fully bleached at pH 6.0 and adjusted immediately to pH 7.5. After addition of equimolar 11-cis-retinal, the absorption was set to zero. The difference spectra were taken at 0.25, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 10, 12, 14, and 15 min, respectively.