FIGURE 5.

TrIQ studies detect that opsin with a constitutively activating mutation induces movement of TM6 toward TM5. A, a bimane label at position 244^6.27 (on TM6) and a tryptophan at position 231^5.66 (on TM5) are expected to show more TrIQ in the active form (and thus decreased fluorescence intensity), based on the respective crystal structures (Protein Data Bank codes 1GZM, 3CAP, and 3PQR). B-E, the emission spectra show ligand-free-labeled opsins in the absence (black) and presence of a Trp at position 231^5.66 (red). B, M257Y/244B-opsin in DDM; C, 244B-opsin in DDM; D, M257Y/244B-opsin in nanodiscs; E, 244B-opsin in nanodiscs. The ratio values of fluorescence intensity in the absence and presence of 231W (F_w/F_o) are also indicated. The experiments were carried out at 10 °C.