TM I–VII: transmembrane α-helical fragments, ECD: extracellular domain (ligand binding domain), EC I–III: extracellular coils, IC I–III: intracellular coils. Fragments removed by alternative splicing are shown by dotted lines. Fragments of ECD and EC III taking part in ligand binding are shown in yellow. Fragment of IC III responsible for G-protein binding shown in blue. Thick red dotted line: disulfide bonds, pink structures: glycosylation sides, orange balls: phosphorylation sides.