Local Conformation Around Position 12 of the (1–34) Fragment of Parathyroid Hormone Probed by Substitution with Aib Residues

Parathyroid hormone (PTH) controls the homeostasis of calcium ions in the blood. Its N-terminal 1–34 fragment is sufficient to reproduce all the physiological functions elicited by the intact hormone. The biologically relevant conformation of PTH(l-34) is thought to include two critical points of flexibility around residue 12 and residue 19 [1]. These two hinges are believed to connect two α-helical regions at either end of the molecule. In order to assess the relationship between biological activity and local conformation around Gly12, we prepared and studied several PTH(1–34) analogs containing Aib residues: [Aib11], [Aib12], [Aib11,12] or [Aib12,13].