Side chain cyclization based on serine residues: synthesis, structure, and activity of a novel cyclic analogue of the parathyroid hormone fragment 1-11

J Med Chem. 2010 Nov 25;53(22):8072-9. doi: 10.1021/jm1008264. Epub 2010 Oct 28.


The N-terminal region of the parathyroid hormone (PTH) is sufficient to activate the G-protein-coupled PTH receptor 1 (PTHR1). The shortest PTH analogue displaying nanomolar potency is the undecapeptide H-Aib-Val-Aib-Glu-Ile-Gln-Leu-Nle-His-Gln-Har-NH(2) that contains two helix-stabilizing residues (Aib(1,3)). To increase the helical character and proteolytic stability of this linear peptide, we replaced Gln(6,10) with (a) Lys(6) and Glu(10) to introduce a lactam bridge and (b) Ser(6,10) to form a diester bridge upon cross-linking with adipic acid. These cyclopeptides were, respectively, 468-fold less and 12-fold more potent agonists than the linear analogue. Despite their different potencies, all three analogues adopted similar α-helix structures, as shown by NMR and molecular dynamics studies. However, the diester bridge could better mimic the orientation and chemical properties of the side chains of Gln(6) and Gln(10) in the linear PTH analogue than the lactam moiety. This is apparently important for efficient receptor activation and provides further insights into the receptor-bound ligand conformation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Circular Dichroism
  • Humans
  • Lactams / chemical synthesis
  • Lactams / chemistry
  • Lactams / pharmacology
  • Lactones / chemical synthesis
  • Lactones / chemistry
  • Lactones / pharmacology
  • Magnetic Resonance Spectroscopy
  • Models, Molecular
  • Molecular Dynamics Simulation
  • Parathyroid Hormone / chemical synthesis*
  • Parathyroid Hormone / chemistry
  • Parathyroid Hormone / pharmacology
  • Peptide Fragments / chemical synthesis*
  • Peptide Fragments / chemistry
  • Peptide Fragments / pharmacology
  • Peptides, Cyclic / chemical synthesis*
  • Peptides, Cyclic / chemistry
  • Peptides, Cyclic / pharmacology
  • Protein Structure, Secondary
  • Receptor, Parathyroid Hormone, Type 1 / agonists*
  • Structure-Activity Relationship


  • Lactams
  • Lactones
  • Parathyroid Hormone
  • Peptide Fragments
  • Peptides, Cyclic
  • Receptor, Parathyroid Hormone, Type 1
  • parathyroid hormone (1-11)