Fig. 5: CDR3-based peptide-mimetics exhibit µOR binding and antagonism.
From: Structural basis of μ-opioid receptor targeting by a nanobody antagonist
a CDR3 conformation of NbE when bound to µOR (left), and peptides synthesized based on CDR3NbE. Peptides 1 to 5 are N-acetylated, C-terminal carboxamides, peptide 6 is an unacetylated C-terminal carboxylic acid for improved solubility. Cyclic peptides 7 and 8 are grafted on the β-turn-inducing D-Pro-L-Pro scaffold. b HTRF competition binding assay profiles of naloxone and NbE (both N = 11), peptide 5 (N = 3), and peptide 6 (N = 7). Binding to HEK293 cells stably expressing SNAP-μOR, labeled with SNAP-Lumi4-Tb, and incubated with 3 nM red-labeled naltrexone derivative. Data normalized to cells without red-labeled naltrexone, mean ± SEM. c Chemical structures of cyclic peptides 7 and 8, with the D-Pro-L-Pro motif colored in blue and anticipated hydrogen bonds in pink. d HTRF competition binding assay profiles of naloxone and NbE (same data as in b), and peptides 7 and 8; N = 3, mean ± SEM. e Reversal of DAMGO-driven inhibition of cAMP accumulation. HEK293 cells stably expressing µOR and treated with 2.5 μM FSK and 10 nM DAMGO = 100% µOR signaling, cells only treated with FSK = 0% µOR signaling. All peptide conditions treated with 10 nM DAMGO and pre-incubated with increasing concentrations of peptides 4–8, N = 4, mean ± SEM. f Reversal of DPDPE-driven inhibition of cAMP accumulation. HEK293 cells stably expressing δOR and treated with 2.5 μM FSK and 1 nM DPDPE = 100% δOR signaling, cells only treated with FSK = 0% δOR signaling. All peptide conditions treated with 1 nM DPDPE and pre-incubated with increasing concentrations of peptides 5, 7, and 8, N = 3, mean ± SEM. In all panels, N indicates the number of independent experiments. Source data are provided as a Source Data files.
