Conformational properties of the proline region of porcine neuropeptide Y by CD and 1H-NMR spectroscopy

✍ Scribed by Shao Song Chu; David Vander Velde; David Shobe; Preeti Balse; Michael B. Doughty

• Publisher: Wiley (John Wiley & Sons)
• Year: 1995
• Tongue: English
• Weight: 912 KB
• Volume: 35
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360350604

✦ Synopsis

We synthesized porcine neuropeptide Y (pNPY) N-terminalfragments by solid-phase synthesis techniques and analyzed them for solution conformational properties by CD and 'H-nmr spectroscopy. The analogues pNPYI-, and pNPYI-,, displayed CD spectra indicative of random structures and showed no evidence for induced a-helical structures in trijluoroethanol (TFE) up to 50%. However, the CD spectra ofpNPY,-, suggested a conformational shift in tetrahydrofuran. Although in aqueous solution the CD spectra o ~P N P Y ~-~, indicated random structures with induction of only a small percentage of a-helix in aqueous TFE, PNPY,-~, displayed 13% ahelical structure in aqueous solution that increased to 40 and 41 % by the addition of TFE and methanol, respectively. The nmr spectra of pNPYI-9 and the proline region ofpNPYI-,, indicated extended structures with all-trans conformers at Pro5 and Pro8 for pNPYI-, and at Pros, Pro& andProl3 forpNPY,-,,; in each case the Tyrl-Pro2 amide bond was in both cis andtrans conformations. However, observed nuclear Overhauser effect correlations and HN exchange experiments indicated an a-helical segment in P N P Y ~-~~ initiated by Pro13 and extendingfrom residues 14 to 25. Thus, the N-terminalpolyproline region ofNPY has no propensity to fold into a regular secondary structure, although Pro13 is a helix initiator, a result consistent with the proposed role of this amino acid in the NPY structural model.