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Conformational properties of the proline region of porcine neuropeptide Y by CD and 1 H‐NMR spectroscopy
Author(s) -
Chu Shao Song,
Velde David Vander,
Shobe David,
Balse Preeti,
Doughty Michael B.
Publication year - 1995
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360350604
Subject(s) - chemistry , proline , nuclear magnetic resonance spectroscopy , neuropeptide , spectroscopy , stereochemistry , biochemistry , amino acid , physics , receptor , quantum mechanics
We synthesized porcine neuropeptide Y (pNPY) N‐terminal fragments by solid‐phase synthesis techniques and analyzed them for solution Conformational properties by CD and 1 H‐nmr spectroscopy. The analogues pNPY 1–9 and pNPY 1–14 displayed CD spectra indicative of random structures and showed no evidence for induced α‐helical structures in trifluoroethanol (TFE) up to 50%. However, the CD spectra of pNPY 1‐9 suggested a Conformational shift in tetrahydrofuran. Although in aqueous solution the CD spectra of pNPY 1–21 indicated random structures with induction of only a small percentage of α‐helix in aqueous TFE, pNPY 1‐25 displayed 13% a‐helical structure in aqueous solution that increased to 40 and 41% by the addition of TFE and methanol, respectively. The nmr spectra of pNPY 1‐9 and the proline region of pNPY 1–25 indicated extended structures with all‐trans conformers at Pro5 and Pro8 for pNPY 1–9 and at Pro5, Pro8, and Pro13 for pNPY 1–25 ; in each case the Tyrl‐Pro2 amide bond was in both cis and trans conformations. However, observed nuclear Overhauser effect correlations and UN exchange experiments indicated an α‐helical segment in pNPY 1–25 initiated by Pro 13 and extending from residues 14 to 25. Thus, the N‐terminal polyproline region of NPY has no propensity to fold into a regular secondary structure, although Pro 13 is a helix initiator, a result consistent with the proposed role of this amino acid in the NPY structural model. © 1995 John Wiley & Sons, Inc.