Role of Asp297 of the AT2 receptor in high-affinity binding to different peptide ligands

To determine how ligand-receptor interaction is affected by the charges of the amino acids at position 2 of the ligands and position 297 of the AT2 receptor, we generated the Asp297Lys mutant of AT2 and a ligand SarAsp 2Ile. Asp297Lys mutant lost affinity to Ang II and SarIle however retained partial affinity to 125I-CGP42112A. The SarAsp 2Ile had high affinity to Asp297Lys (IC 503.5nM) and partial affinity to the AT2 (IC 5015nM). Therefore, not only the charge, but also the length of the side arms of the amino acids at position 2 of the ligand and position 297 of the receptor affect their interaction.