3-DIMENSIONAL STRUCTURE OF THE Y1 RECEPTOR AGONIST [LEU(31), PRO(34)]NPY AS DETERMINED BY NMR AND MOLECULAR MODELING

The solution structure of the Y1 receptor agonist, porcine [Leu(31), P ro(34)]NPY, has been investigated by two-dimensional NMR and molecular modeling. A complete assignment of the NMR resonances was achieved an d 201 inter-residue nuclear Overhauser enhancement spectroscopy (NOESY ) connectivities could be identified, comprising several connectivitie s between the N- and C-terminal segments. A molecular model was calcul ated by distance geometry, simulated annealing and conjugate gradients energy minimization using the NOE constraints. The results indicate t hat, like NPY and other peptides of the family, [Leu(31), Pro(34)]NPY adopts a folded hairpin structure with the terminal segments in close proximity. Analysis of the secondary chemical shifts for the CH alpha' s and of the temperature dependence of the NH chemical shifts combined with the NOE constraints indicates a tendency toward helix structure for the segment 18-30 and the presence of turn structure for the C-ter minal segment (residues 31-36). Native NPY and [Leu(31), Pro(34)]NPY h ave most of their structures in common but differ slightly in their C- terminal portion. Based on the structures of NPY and of its specific a gonists, [Leu(31), Pro(34)]NPY and NPY 13-36, conclusions can be drawn about the structural requirements for binding to the Y1 and Y2 recept or subtypes. (C) Munksgaard 1998.