Strongly altered receptor binding properties in PP and NPY chimeras are accompanied by changes in structure and membrane binding.
Neuropeptide Y (NPY) and the pancreatic polypeptide (PP) are members of the neuropeptide Y family of hormones. They bind to the Y receptors with very different affinities: Whereas PP is highly selective for the Y(4) receptor, NPY displays highest affinites for Y(1), Y(2), and Y(5) receptor subtypes. Introducing the NPY segment 19-23 into PP leads to an increase in affinity at the Y(1) and Y(2) receptor subtypes whereas the exchange of this segment from PP into NPY leads to a large decrease in affinity at all receptor subtypes. PP displays a very stable structure in solution, with the N terminus being back-folded onto the C-terminal alpha-helix (the so-called PP-fold). The helix of NPY is less stable and the N terminus is freely diffusing in solution. The exchange of this segment, however, does not alter the PP-fold propensities of the chimeric peptides in solution. The structures of the phospholipid micelle-bound peptides serving to mimic the membrane-bound species display segregation into a more flexible N-terminal region and a well-defined alpha-helical region. The introduction of the [19-23]-pNPY segment into hPP leads to an N-terminal extension of the alpha-helix, now starting at Pro(14) instead of Met(17). In contrast, a truncated helix is observed in [(19)(-)(23)hPP]-pNPY, starting at Leu(17) instead of Ala(14). All peptides display moderate binding affinities to neutral membranes (K(assoc) in the range of 1.7 to 6.8 x 10(4) mol(-)(1) as determined by surface plasmon resonance) with the differences in binding being most probably related to the exchange of Arg-19 (pNPY) by Glu-23 (hPP). Differences in receptor binding properties between the chimeras and their parental peptides are therefore most likely due to changes in the conformation of the micelle-bound peptides.
Lerch
Mirjam
M
Institute of Pharmaceutical Sciences, ETH Zurich, Switzerland. mirjam@dbb.su.se
Kamimori
Hiroshi
H
Folkers
Gerd
G
Aguilar
Marie-Isabel
MI
Beck-Sickinger
Annette G
AG
Zerbe
Oliver
O
D000818:Animals; D002417:Cattle; D002462:Cell Membrane / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D020128:Inhibitory Concentration 50; D008958:Models, Molecular; D009478:Neuropeptide Y / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D019906:Nuclear Magnetic Resonance, Biomolecular; D010191:Pancreatic Polypeptide / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017476:Receptors, Neuropeptide Y / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012996:Solutions; D013552:Swine
D009478:Neuropeptide Y; D010446:Peptide Fragments; D017476:Receptors, Neuropeptide Y; D011993:Recombinant Fusion Proteins; D012996:Solutions; D010191:Pancreatic Polypeptide