Binding specificity of the ectodomain of the parathyroid hormone receptor

The parathyroid hormone (PTH)1 receptor is a member of the class B G protein-coupled receptor (GPCR) family and regulates bone and mineral metabolism of vertebrates. A truncated highly active parathyroid hormone fragment PTH (1-34) exerts stimulatory effects on the receptor and is used for treatment of osteoporosis. To study the interacting amino acids of the natural peptide ligand PTH (1-84) with the ectodomain of its receptor we used peptide micro arrays on solid cellulose membranes. The amino acids Arg20 and Trp23 within the identified core binding stretch PTH (20-26) were found to be most important for affinity to the ectodomain of PTH1R. Isothermal titration calorimetry and NMR spectroscopy allowed peptide binding studies in solution and verified peptide positions required for high affinity. With this combination of biochemical and biophysical methods we extend former findings on this essential interaction and can now provide a strategy to screen for optimized therapeutic peptides.

Graphical AbstractDownload full-size imageResearch Highlights► Pin point GPCR ECD-binding competent stretch of parathyroid hormone PTH (1-84). ► Narrow this stretch down to a core peptide region: PTH (20-26). ► Identify single residues crucial for binding: Arg20, Trp23. ► Determine binding affinities of peptide variants in solution by ITC. ► Measure dynamic interaction in the PTH-nPTH1R complex by NMR at residue resolution.