Identification of a contact site for residue 19 of parathyroid hormone (PTH) and PTH-related protein analogs in transmembrane domain two of the type 1 PTH receptor

Mol Endocrinol. 2003 Dec;17(12):2647-58. doi: 10.1210/me.2003-0275. Epub 2003 Aug 28.


Recent functional studies have suggested that position 19 in PTH interacts with the portion of the PTH-1 receptor (P1R) that contains the extracellular loops and seven transmembrance helices (TMs) (the J domain). We tested this hypothesis using the photoaffinity cross-linking approach. A PTHrP(1-36) analog and a conformationally constrained PTH(1-21) analog, each containing para-benzoyl-l-phenylalanine (Bpa) at position 19, each cross-linked efficiently to the P1R expressed in COS-7 cells, and digestive mapping analysis localized the cross-linked site to the interval (Leu232-Lys240) at the extracellular end of TM2. Point mutation analysis identified Ala234, Val235, and Lys240 as determinants of cross-linking efficiency, and the Lys240-->Ala mutation selectively impaired the binding of PTH(1-21) and PTH(1-19) analogs, relative to that of PTH(1-15) analogs. The findings support the hypothesis that residue 19 of the receptor-bound ligand contacts, or is close to, the P1R J domain-specifically, Lys240 at the extracellular end of TM2. The findings also support a molecular model in which the 1-21 region of PTH binds to the extracellular face of the P1R J domain as an alpha-helix.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Substitution
  • Animals
  • Binding Sites
  • COS Cells
  • Chlorocebus aethiops
  • Humans
  • Models, Molecular
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Parathyroid Hormone / chemistry*
  • Parathyroid Hormone-Related Protein / chemistry*
  • Peptide Fragments / chemistry
  • Protein Conformation
  • Rats
  • Receptor, Parathyroid Hormone, Type 1
  • Receptors, Parathyroid Hormone / chemistry*
  • Receptors, Parathyroid Hormone / genetics
  • Receptors, Parathyroid Hormone / metabolism
  • Transfection


  • PTH1R protein, human
  • Parathyroid Hormone
  • Parathyroid Hormone-Related Protein
  • Peptide Fragments
  • Receptor, Parathyroid Hormone, Type 1
  • Receptors, Parathyroid Hormone