Opioid receptor random mutagenesis reveals a mechanism for G protein-coupled receptor activation

Nat Struct Biol. 2003 Aug;10(8):629-36. doi: 10.1038/nsb950.


The high resolution structure of rhodopsin has greatly enhanced current understanding of G protein-coupled receptor (GPCR) structure in the off-state, but the activation process remains to be clarified. We investigated molecular mechanisms of delta-opioid receptor activation without a preconceived structural hypothesis. Using random mutagenesis of the entire receptor, we identified 30 activating point mutations. Three-dimensional modeling revealed an activation path originating from the third extracellular loop and propagating through tightly packed helices III, VI and VII down to a VI-VII cytoplasmic switch. N- and C-terminal determinants also influence receptor activity. Findings for this therapeutically important receptor may apply to other GPCRs that respond to diffusible ligands.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Binding Sites
  • Cell Line
  • Humans
  • In Vitro Techniques
  • Models, Molecular
  • Mutagenesis
  • Point Mutation
  • Protein Structure, Tertiary
  • Receptors, G-Protein-Coupled / chemistry*
  • Receptors, G-Protein-Coupled / genetics*
  • Receptors, G-Protein-Coupled / metabolism
  • Receptors, Opioid, delta / chemistry*
  • Receptors, Opioid, delta / genetics*
  • Receptors, Opioid, delta / metabolism
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism


  • Receptors, G-Protein-Coupled
  • Receptors, Opioid, delta
  • Recombinant Proteins

Associated data

  • PDB/1OZC