Figure 1: Structure of bR in dark-state determined by SFX.

In side view (a) and perpendicular to the membrane (b). The retinal is shown as yellow sticks and the Lys216 side chain covalently binding retinal as blue sticks. Continuous 2Fo−Fc electron density map around retinal and lysine is shown in magenta. Helices A–G are defined based on the header of pdb entry 1QHJ (TM A: 6–32; TM B: 37–58; TM C: 80–100; TM D: 105–127; TM E: 131–160; TM F:165–191; and TM G: 201–224).