Structure-activity relationships of a series of analogues of the RFamide-related peptide 26RFa

J Med Chem. 2011 Jul 14;54(13):4806-14. doi: 10.1021/jm200418c. Epub 2011 Jun 9.


26RFa is a new member of the RFamide peptide family that has been identified as the endogenous ligand of the orphan GPCR GPR103. As the C-terminal heptapeptide (26RFa((20-26))) mimics the action of the native peptide on food intake and gonadotropin secretion in rodents, we have synthesized a series of analogues of 26RFa((20-26)) and measured their potency to induce [Ca(2+)](i) mobilization in Gα(16)-hGPR103-transfected CHO cells. Systematic replacement of each residue by an alanine (Ala scan) and its D-enantiomer (D scan) showed that the last three C-terminal residues were very sensitive to the substitutions while position 23 tolerated rather well both modifications. Most importantly, replacement of Ser(23) by a norvaline led to an analogue, [Nva(23)]26RFa((20-26)), that was 3-fold more potent than the native heptapeptide. These new pharmacological data, by providing the first information regarding the structure-activity relationships of 26RFa analogues, should prove useful for the rational design of potent GPR103 receptor ligands with potential therapeutic application.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • CHO Cells
  • Calcium / metabolism
  • Cricetinae
  • Cricetulus
  • GTP-Binding Protein beta Subunits / metabolism
  • Ligands
  • Neuropeptides / chemical synthesis
  • Neuropeptides / chemistry*
  • Neuropeptides / pharmacology
  • Receptors, G-Protein-Coupled / agonists
  • Receptors, G-Protein-Coupled / antagonists & inhibitors
  • Receptors, G-Protein-Coupled / metabolism*
  • Stereoisomerism
  • Structure-Activity Relationship
  • Transfection


  • GTP-Binding Protein beta Subunits
  • Ligands
  • Neuropeptides
  • QRFPR protein, human
  • Receptors, G-Protein-Coupled
  • prepro-26RFa protein, human
  • arginylphenylalaninamide
  • Calcium