FIGURE 1.

Top, two views of the superposition of the three-dimensional models of the N-terminal domain of glucagon receptor constructed using the GIPR and GLP-1R crystal structures. The models built with GIPR and GLP-1R are represented by a purple and green ribbon, respectively. The three disulfide bridges, Asp⁶³, Lys⁹⁸, and Arg¹¹⁶ are depicted as sticks and colored according to the following color scheme (cyan, carbon; red, oxygen; blue, nitrogen; yellow, sulfur). A salt bridge is formed between Asp⁶³ and Arg¹¹⁶. Similar interactions are observed in the respective x-ray structure templates. Bottom, multiple sequence alignment of the human N-terminal domains of the glucagon, GIP, and GLP-1 receptors used to generate the three-dimensional models of the glucagon receptor. Sequence identity is highlighted in gray.