The neuropeptide Y monomer in solution is not folded in the pancreatic-polypeptide fold.
Fluorescence-labelled analogs of NPY, a 36-amino acid peptide amide, were synthesized by solid-phase peptide synthesis and used for fluorescence-resonance energy transfer studies to investigate the conformation. Energy-transfer efficiency measurements in different media at the concentration of 10 microM are in agreement with a model of the NPY structure proposed by NMR studies (performed at millimolar concentration) in which the C-terminal part of the molecule adopts an alpha-helical conformation while the N-terminal part is flexible. According to this model, the alpha-helix is stabilized by intermolecular hydrophobic interactions because of the formation of dimers. The decrease of the peptide concentration causes a shift of the dimerization equilibrium toward the monomeric form. Energy-transfer efficiency measurements performed at lower concentrations do not support the hypothesis of the folding back of the N-terminal tail onto the C-terminal alpha-helix to yield the so-called "PP-fold" conformation. This structure is observed in the crystal structure of avian pancreatic polypeptide, a member of the NPY peptide hormone family, and it has been considered to be the bioactive one. Our results complete the structural characterization of NPY in solution at concentration ranges in which NMR experiments are not feasible. Furthermore, these results open the way to study the conformation of the receptor-bound ligand.
Bettio
Andrea
A
Institute of Biochemistry, University of Leipzig, Talstrasse 33, D-04103 Leipzig, Germany.
Dinger
Michaela C
MC
Beck-Sickinger
Annette G
AG
D000595:Amino Acid Sequence; D000818:Animals; D002942:Circular Dichroism; D019791:Guanidine / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D009478:Neuropeptide Y / Q000737:chemistry* / Q000378:metabolism; D011138:Polytetrafluoroethylene / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D012996:Solutions; D013050:Spectrometry, Fluorescence; D013552:Swine
D009478:Neuropeptide Y; D012996:Solutions; D011138:Polytetrafluoroethylene; D019791:Guanidine