Structure-activity relationships of peptides incorporating a bioactive reverse-turn heterocycle at the melanocortin receptors: identification of a 5800-fold mouse melanocortin-3 receptor (mMC3R) selective antagonist/partial agonist versus the mouse melanocortin-4 receptor (mMC4R)

J Med Chem. 2013 Apr 11;56(7):2747-63. doi: 10.1021/jm301253y. Epub 2013 Mar 25.


The melanocortin-3 (MC3) and melanocortin-4 (MC4) receptors regulate energy homeostasis, food intake, and associated physiological conditions. The melanocortin-4 receptor (MC4R) has been studied extensively. Less is known about specific physiological roles of the melanocortin-3 receptor (MC3R). A major obstacle to this lack of knowledge is attributed to a limited number of identified MC3R selective ligands. We previously reported a spatial scanning approach of a 10-membered thioether-heterocycle ring incorporated into a chimeric peptide template that identified a lead nM MC4R ligand. Upon the basis of those results, 17 compounds were designed and synthesized that focused upon modification in the pharmacophore domain. Notable results include the identification of a 0.13 nM potent 5800-fold mMC3R selective antagonist/slight partial agonist versus a 760 nM mMC4R full agonist (ligand 11). Biophysical experiments (two-dimensional (1)H NMR and computer-assisted molecular modeling) of this ligand resulted in the identification of an inverse γ-turn secondary structure in the ligand pharmacophore domain.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Mice
  • Nuclear Magnetic Resonance, Biomolecular
  • Peptides / chemistry*
  • Peptides / pharmacology*
  • Receptors, Melanocortin / agonists
  • Receptors, Melanocortin / antagonists & inhibitors
  • Receptors, Melanocortin / chemistry*
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
  • Structure-Activity Relationship


  • Peptides
  • Receptors, Melanocortin