Residue 19 of the parathyroid hormone: structural consequences

Biochemistry. 2002 Nov 5;41(44):13217-23. doi: 10.1021/bi0261600.

Abstract

Residue 19 of the parathyroid hormone (PTH) has been shown to play an important role in both binding to and activation of the PTH receptor; specifically, Arg(19)-containing analogues have improved biological function over similar Glu(19) peptides [Shimizu et al. (2002) Biochemistry 41, 13224-13233]. Additionally the juxtamembrane portion of the receptor is involved in the different biological responses. Here, we determine the conformational preferences of PTH analogues to provide a structural basis for their biological actions. On the basis of circular dichroism results, the Arg(19) --> Glu(19) mutations within the context of both PTH(1-20) and PTH(1-34) analogues lead to increases in helix content, ranging from a 8-15% increase. High-resolution structures as determined by (1)H NMR and NOE-restrained molecular dynamics simulations clearly illustrate the difference between Arg(19) and Glu(19)-PTH(1-20), particularly with the extent and stability of the C-terminal helix. The Arg(19)-containing analogue has a well defined, stable alpha-helix from Ser(4)-Arg(19), while the Glu(19) analogue is less ordered at the C-terminus. On the basis of these observations, we propose that position 19 of PTH(1-20) must be alpha-helical for optimal interaction with the juxtamembrane portion of the receptor. This mode of binding extends the current view of PTH binding (indeed ligand binding for all class B GPCRs), which invokes a bihelical ligand with the C-terminus of the ligand interacting with the N-terminus of the receptor (responsible for binding) and the N-terminus of the ligand interacting with the seven-helical bundle (leading to receptor activation).

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Substitution / genetics
  • Arginine / chemistry
  • Arginine / genetics
  • Circular Dichroism
  • Computer Simulation
  • Glutamic Acid / chemistry
  • Glutamic Acid / genetics
  • Ligands
  • Molecular Sequence Data
  • Nuclear Magnetic Resonance, Biomolecular
  • Parathyroid Hormone / chemistry*
  • Parathyroid Hormone / genetics
  • Parathyroid Hormone / metabolism
  • Parathyroid Hormone / physiology
  • Peptide Fragments / chemical synthesis
  • Peptide Fragments / genetics
  • Peptide Fragments / physiology
  • Receptors, Parathyroid Hormone / chemistry

Substances

  • Ligands
  • Parathyroid Hormone
  • Peptide Fragments
  • Receptors, Parathyroid Hormone
  • Glutamic Acid
  • Arginine