The TM6-TM7 interface in β
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 β2ARINV (left) C6.47 forms a hydrogen bond with N7.45 and eventually with the backbone of 6.43; in β2ARAGO (right) the hydrogen bond between 6.47 and N7.45 is broken and C6.47 interacts only with the backbone of 6.43. C) sRHOINV features Q6.43 bridging S6.47 and S7.45. D) In RHOINV (left) C6.47 is interacting with T7.44 g+; in RHOAGO the hydrogen bond between Cys 6.47 and T7.44 has broken. Color code is as follows: TM6 (blue), TM7 (pale red).