Side chain modifications change the binding and agonist properties of endomorphin 2

Biochem Biophys Res Commun. 2002 Jan 11;290(1):153-61. doi: 10.1006/bbrc.2001.6136.

Abstract

Side chain modifications were introduced to endomorphin 2 (E2) to improve its binding properties and biological activity. A number of C-terminal modifications decreased the binding affinity to the mu-opioid receptor and the intrinsic activity in rat brain membranes. The exception was E2-ol, which showed increased binding affinity to MOR and higher potency in stimulating [(35)S]GTPgammaS binding. N-methylation of Phe(3) (MePhe(3)) attenuated the binding affinity and produced a rightward shift of [(35)S]GTPgammaS binding curves. All derivatives had lower intrinsic activity than E2. Some of the modified peptides partially inhibited, while YPF-benzyl-allyl-amide fully inhibited, the E2 or [d-Ala(2),MePhe(4),Gly(5)ol]enkephalin stimulated [(35)S]GTPgammaS binding. Marked differences were found between the results obtained using tritiated E2, tritiated naloxone, and [(35)S]GTPgammaS binding, indicating the possible involvement of multiple binding sites. The data presented demonstrate that the C-terminal amide group has an essential role in the regulation of the binding and the agonist/antagonist properties of E2.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding Sites
  • Brain / metabolism
  • Cell Membrane / metabolism
  • Dose-Response Relationship, Drug
  • Inhibitory Concentration 50
  • Kinetics
  • Ligands
  • Models, Chemical
  • Mutagenesis, Site-Directed
  • Naloxone / pharmacology
  • Oligopeptides / chemistry*
  • Oligopeptides / metabolism*
  • Peptides / chemistry
  • Protein Binding
  • Protein Conformation
  • Protein Structure, Tertiary
  • Rats
  • Rats, Wistar
  • Receptors, Opioid, mu / chemistry

Substances

  • Ligands
  • Oligopeptides
  • Peptides
  • Receptors, Opioid, mu
  • Naloxone
  • endomorphin 2