Fig. 3.

Bioactive domains and key functional determinants of PTH(1–34) receptor ligands. (A) Shown is the sequence of the bioactive (1–34) segment of parathyroid hormone in linear format with residues in the amino-terminal portion that are critical for signaling shown in blue and those in the C-terminal domain that are critical for binding shown in red. (B) The PTH(1–34) ligand is presented in three-dimensional ribbon format to display the two-helical-domain structure typically observed in solution-phase NMR studies, with the side chains shown of the key binding and signaling residues. The structure was generated using the solution-phase NMR-derived coordinate file PDB ID 1HPH deposited in the Protein Data Bank (Marx et al., 1995).