Probing the functional conformation of neuropeptide Y through the design and study of cyclic analogues.
The functional importance of the PP-fold conformation in neuropeptide Y (NPY) was investigated. NPY and N alpha-Ac-NPY(10-36), and corresponding cyclic analogues cyclo18,22-[Lys18,Asp22]-NPY and N alpha-Ac-cyclo18,22-[Lys18,Asp22]-NPY(10-36), were synthesized. Strategies for synthesis of the cyclic analogues included the use of the Kaiser oxime resin and a segment condensation approach. Circular dichroism studies in phosphate buffer, pH 5.0, indicated self-association of all four peptides at low micromolar concentrations. Monomeric N alpha-Ac-NPY(10-36) showed only 13% alpha-helix, compared to 32% alpha-helix for monomeric NPY, demonstrating a helix-stabilizing effect of residues 1-9 that is consistent with the PP fold. The [Lys18,Lys22] lactam bridge stabilized the helical conformation in N alpha-Ac-NPY(10-36)(51% alpha-helix), but was helix destabilizing in NPY (21% alpha-helix). In rat brain receptor binding assays, the cyclic and linear N alpha-Ac-NPY(10-36) analogues were equipotent (IC50 = 13 nM for 125I-BH-NPY displacement), although the cyclic analogue was twice as potent in rat vas deferens assays. NPY was more potent than its cyclic analogue in the brain receptor binding assays (IC50 = 0.07 and 0.25 nM, respectively), but these peptides were equipotent in the vas deferens assays. These results support a functional role for the PP fold in NPY and correlate with the solution conformations of the monomeric peptides.
Bouvier
M
M
Laboratory of Bioorganic Chemistry and Biochemistry, Rockefeller University, New York, New York 10021.
Taylor
J W
JW
D000818:Animals; D002942:Circular Dichroism; D008297:Male; D009478:Neuropeptide Y / Q000031:analogs & derivatives*; D009479:Neuropeptides / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013329:Structure-Activity Relationship
D009478:Neuropeptide Y; D009479:Neuropeptides