CONFORMATION OF PARATHYROID-HORMONE ANTAGONISTS BY CD, NMR, AND MOLECULAR-DYNAMICS SIMULATIONS

The conformation of two highly potent parathyroid hormone (PTH) antago nists was investigated in water /2,2, 2-trifluoroethanol mixtures. The two peptides are derived from the sequence (7-34) of PTH and of PTH-r elated protein (PTHrP) and have a D-Trp replacing Gly in position 12. In the analogue derived from PTHrP, Lys(11) was replaced by Leu to rem ove the residual agonist activity. The study was conducted by CD and t wo-dimensional proton magnetic resonance spectroscopy and the nuclear Overhauser effects found weve utilized in restrained distance geometry and molecular dynam ics simulations. Both peptides adopt a helical C- terminal conformation, which seems move stable in the case of the PTHr P analogue. A type II' beta-turn centered around D-Trp(12) and Lys(13) is present in both structures. (C) 1995 John Wiley & Sons, Inc.