Fig. 4: Binding modes of formyl peptides at FPR1 and FPR2.

a–c Interactions between FPR2 and the formyl peptides. Only the receptor in the fM5–FPR2–G_i2 (a, b) or fM9–FPR2–G_i2 structure (c) is shown in cartoon representation for clarity. a Interactions between FPR2 and the residues Y/L2 and I4 in fM5 and fM9. b Interactions between FPR2 and the residues F3 and I5/I6 in fM5 and fM9. c Interactions between FPR2 and the residues N5 and L7 in fM9. Polar interactions are shown as red dashed lines. d Interactions between FPR1 and the residues L2 and F3 in fMLF. The peptide fM5 and FPR2 residues L81^2.60 and F257^6.51 in the fM5–FPR2–G_i2 structure are also shown for comparison. The red arrow indicates the movement of fMLF relative to fM5. e, f Surfaces of the FPRs are colored according to their electrostatic potential from red (negative) to blue (positive), showing different charge distributions at the entrance to the ligand-binding pocket in the two receptors. e The peptide fMLF and the receptor residues R84^2.63, K85^2.64, G89, and G280^7.32 in the fMLF–FPR1–G_i1 structure are shown as sticks. f The receptor residues S84^2.63, M85^2.64, E89, and D281^7.32 in the fM9–FPR2–G_i2 structure are shown as sticks. The peptide fMLF in the fMLF–FPR1–G_i1 structure is also shown. The green “x” indicates that the negatively charged C terminus of fMLF repels the acidic residues E89 and D281^7.32 in FPR2.