Fig. 29.8 Overlay of the crystal structures of the AT1 receptor with the bound octapeptide angiotensin II 29.20 (yellow, inner surface yellow, outside red) and the low molecular weight sartan-like ligand 29.21 (green, inner surface green, outside blue). For crystallization, the receptor was stabilized with an antibody (not shown in the figure). The C-terminal acid function of 29.20 forms a hydrogen bond to Lys 199, and the tetrazole of 29.21 interacts with Arg 167. Structure determination suggests that the binding domains of angiotensin II and the sartans overlap spatially.