FIGURE 5.
Meta II decay and Gt activation assays of purified WT (black line) and P23H (gray line) isorhodopsin in detergent. A, Meta II decay of isorhodopsin is shown by the time course of changes in Trp fluorescence at 330 nm. Decay rates (τ) of WT isorhodopsin and P23H Meta II isorhodopsin are listed in the insets of A. B, results of a Gt activation assay of isorhodopsin are shown by the time course of Trp fluorescence at 345 nm due to guanylyl nucleotide exchange. The pseudo-first order kinetic rate (k) of Gt activation (derived from the function A(t) = Amax(1 − exp−kt)), where Amax is the maximal Gt fluorescence change, and A(t) is the relative fluorescence change at time (t) for WT isorhodopsin shown in the inset of B. Purified P23H isorhodopsin in detergent did not activate Gt.