The Importance of Ligand-Receptor Conformational Pairs in Stabilization: Spotlight on the N/OFQ G Protein-Coupled Receptor

Structure. 2015 Dec 1;23(12):2291-2299. doi: 10.1016/j.str.2015.07.024. Epub 2015 Oct 29.


Understanding the mechanism by which ligands affect receptor conformational equilibria is key in accelerating membrane protein structural biology. In the case of G protein-coupled receptors (GPCRs), we currently pursue a brute-force approach for identifying ligands that stabilize receptors and facilitate crystallogenesis. The nociceptin/orphanin FQ peptide receptor (NOP) is a member of the opioid receptor subfamily of GPCRs for which many structurally diverse ligands are available for screening. We observed that antagonist potency is correlated with a ligand's ability to induce receptor stability (Tm) and crystallogenesis. Using this screening strategy, we solved two structures of NOP in complex with top candidate ligands SB-612111 and C-35. Docking studies indicate that while potent, stabilizing antagonists strongly favor a single binding orientation, less potent ligands can adopt multiple binding modes, contributing to their low Tm values. These results suggest a mechanism for ligand-aided crystallogenesis whereby potent antagonists stabilize a single ligand-receptor conformational pair.

Keywords: BRET; G protein-coupled receptor; GPCR; N/OFQ; NOP; Nociceptin/orphanin FQ peptide receptor; ORL-1; lipidic cubic phase; membrane protein; opioid receptor; receptor-ligand conformational pair.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Binding Sites
  • Cycloheptanes / pharmacology
  • HEK293 Cells
  • Humans
  • Ligands
  • Molecular Docking Simulation
  • Molecular Sequence Data
  • Nociceptin Receptor
  • Piperidines / pharmacology
  • Protein Binding
  • Receptors, Opioid / chemistry*
  • Receptors, Opioid / metabolism


  • Cycloheptanes
  • Ligands
  • Piperidines
  • Receptors, Opioid
  • cis-1-methyl-7-((4-(2,6-dichlorophenyl)piperidin-1-yl)methyl)-6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ol
  • Nociceptin Receptor
  • OPRL1 protein, human

Associated data

  • PDB/5DHG
  • PDB/5DHH