Figure 2

The TM6-TM7 interface in β ₂ AR^INV structure. A) Hydrophobic residues (white surface) and free carbonyl groups (red) surrounding C6.47 (grey surface). B-D) Hydrogen bond network at the TM6 and TM7 interface (indicated by dotted lines). B) In β₂AR^INV (left) C6.47 forms a hydrogen bond with N7.45 and eventually with the backbone of 6.43; in β₂AR^AGO (right) the hydrogen bond between 6.47 and N7.45 is broken and C6.47 interacts only with the backbone of 6.43. C) sRHO^INV features Q6.43 bridging S6.47 and S7.45. D) In RHO^INV (left) C6.47 is interacting with T7.44 g+; in RHO^AGO the hydrogen bond between Cys 6.47 and T7.44 has broken. Color code is as follows: TM6 (blue), TM7 (pale red).