1 The Beckman Research Institute of the City of Hope, Duarte, California, 91010-0269; 2 Durham Veterans Affairs and Duke University Medical Centers, Durham, North Carolina, 27705; 3 CURE Digestive Diseases Research Center, Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles 90073; and 4 Digestive Diseases Division, UCLA School of Medicine, Los Angeles, California 90095
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ABSTRACT |
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We synthesized PYY-(1-36) (nonselective between Y1 and Y2 receptor subtype agonists), [Pro34]PYY (selective for Y1), and PYY-(3-36) (selective for Y2) to determine whether solution conformation plays a role in receptor subtype selectivity. The three peptides exhibited the expected specificities in displacing labeled PYY-(1-36) from cells transfected with Y1 receptors (dissociation constants = 0.42, 0.21, and 1,050 nM, respectively) and from cells transfected with Y2 receptors (dissociation constants = 0.03, 710, and 0.11 nM, respectively) for PYY-(1-36), [Pro34]PYY, and PYY-(3-36). Sedimentation equilibrium analyses revealed that the three PYY analogs were 80-90% monomer at the concentrations used for the subsequent circular dichroism (CD) and 1H-nuclear magnetic resonance (NMR) studies. CD analysis measured helicities for PYY-(1-36), [Pro34]PYY, and PYY-(3-36) of 42%, 31%, and 24%, suggesting distinct differences in secondary structure. The backbone 1H-NMR resonances of the three peptides further substantiated marked conformational differences. These patterns support the hypothesis that Y1 and Y2 receptor subtype binding affinities depend on the secondary and tertiary solution state structures of PYY and its analogs.
peptide YY; Y1 receptor; Y2 receptor; circular dichroism; nuclear magnetic resonance; three-dimensional structure
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INTRODUCTION |
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THE PANCREATIC POLYPEPTIDE family is comprised of three naturally occurring bioactive peptides, pancreatic polypeptide (PP), neuropeptide Y (NPY), and peptide YY (PYY), that are found in the gut and brain. PYY is released from endocrine L cells of the distal digestive tract by indirect stimulation from the proximal gut through neural and humoral pathways and by direct stimulation of L cells by luminal contents (7, 16). Two endogenous forms of PYY, PYY-(1-36) and PYY-(3-36), are released into the circulation by a meal (15). Proposed gastrointestinal actions of PYY are inhibition of gastric secretion, inhibition of pancreatic secretion, inhibition of intestinal secretion, and inhibition of gastrointestinal motility (1, 4, 8, 26, 27, 29).
PYY binds and activates at least three receptor subtypes
(Y1, Y2, and Y5) in rats and
humans, and it may interact with a postulated fourth subtype, the
peripheral Y2-like receptor. Here we use the nomenclature
for Y receptors suggested by the International Union of Pharmacology
(5). These Y receptor subtypes display different patterns of
affinity and activation for the two endogenous ligands PYY and
PYY-(3-36) and for the two synthetic analogs
[Pro34]PYY and [D-Trp32]PYY. In
general, the Y1 receptor subtype has high affinity for PYY
and [Pro34]PYY, the Y2 has high
affinity for PYY and PYY-(3-36), and the Y5 subtype binds PYY, PYY-(3-36),
[Pro34]PYY, and [D-Trp32]PYY
with high affinity. Figure 1 shows the
primary structures of the agonists used in our studies. These different
patterns of receptor selectivity could be caused by differences in
primary structure, differences in tertiary structure due to altered
conformations of the ligands in solution, or both.
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Early descriptions of the structure of avian PP were derived from analysis of X-ray crystallography data (6), which led to modeling of potential structures of mammalian PP, NPY, and PYY by computer analysis (14). The solution structures of PP and of NPY have been studied by circular dichroism (CD) and nuclear magnetic resonance (NMR) (11, 12, 19, 23, 24, 28). All analyses of PP have consistently found evidence for a folded structure (the "PP fold") stabilized by hydrophobic interactions among residues in the NH2- and COOH-terminal portions. A similar structure has been assumed to exist for NPY and PYY because of their high sequence homologies to PP.
Such results have led to hypotheses that this stable structure of PP family peptides is critical for binding and activation of PP/NPY/PYY-specific receptors and that receptor selectivity depends in part on differences in solution structure produced by amino acid deletions or substitutions in naturally occurring or synthetic Y receptor agonists. The purpose of this study was to determine whether removing amino acids from the NH2 terminus of PYY [to form PYY-(3-36)] or substitution of glutamine at position 34 with a proline (to form [Pro34]PYY) causes secondary and tertiary structure changes in the peptide that could contribute to Y receptor selectivity.
In previous work, models of the conformation of NPY were confounded by
the presence of molecular dimerization under the solution conditions
used to generate CD and NMR data, requiring cautious interpretation of
results when attempting to extend the structure model to receptor
binding. Thus, although the proposed role of stable solution structure
of Y receptor agonists in binding, activation, and receptor subtype
selectivity is an attractive possibility that could be a model for
understanding the contribution of tertiary structure to bioactivity of
peptide ligands, it is supported only by indirect evidence. The PP fold
that has been used as a model for PYY and NPY tertiary structure is
based on conformations that have been determined for the tertiary
structures of avian and bovine PP (6, 19).
Modeling based on the PP fold (rather than on directly determined NPY
structures) was necessary for NPY because three groups found that the
peptide formed a head-to-toe dimer between amphipathic -helices
formed from residues 13-36 (the NH2-terminal residues were
flexible in solution) (11, 24, 28). However, Darbon et al. (12) reported a
monomeric NPY structure with a tertiary fold similar to the PP
fold. The solution structures of the monomeric forms of
these peptides are important because NPY and PYY occur as monomers
under physiological concentrations, i.e., <1 nM, in the circulation.
Only limited structural studies have been performed on PYY and on NPY and PYY agonists. Analyses of the secondary structures of PYY and its analogs by CD have revealed that two analogs with NH2-terminal changes had greater helicity and more potent bioactivity, suggesting that tertiary structure could influence activity (22). Furthermore, other studies showed that NPY helicity decreased as NH2-terminal amino acids were removed (17) and that helical content could be disrupted by single D-amino acid substitutions for natural L-forms (18) or by substitution of alanine for natural amino acids (3).
In this study, we demonstrate with CD and one-dimensional (1-D) NMR spectra that altering the primary structure of PYY significantly changes the secondary and tertiary structure of these analogs. These findings are consistent with the proposed role of three-dimensional (3-D) conformation in determining receptor subtype selectivity.
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METHODS |
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Peptides. Porcine PYY-(1-36), PYY-(3-36), and [Pro34]PYY-(1-36) were synthesized in the UCLA Peptide Synthesis Facility using 9-fluorenylmethyloxycarbonyl (FMOC) strategy on an Advanced Chem Tech 396 Peptide Synthesizer. The peptides were cleaved from the resin, protecting groups were removed, and the peptides were then purified to >90% as evaluated by high-performance capillary electrophoresis.
Analytical ultracentrifugation. The sedimentation equilibrium analyses for PYY analogs were performed at UCLA in the laboratory of Prof. V. Shumaker on a Beckman Optima XLA analytical ultracentrifuge. Three samples of each peptide at 0.1, 0.7, and 2 mM (in 150 mM KCl, pH 5.0, at 21°C) were centrifuged at 40,000 and 32,000 rpm using a 12-mm six-channel cell until equilibrium was established. Approximate molecular weights were determined by assuming a single species and fitting the absorbance at 290 nm vs. radius data by nonlinear regression analysis. A molecular weight higher than the calculated peptide mass indicates self-association and can be fit to a monomer-dimer (or higher order) model.
CD and NMR. The CD experiments were performed on a Jasco J-600 spectropolarimeter (Easton, MD). A 0.1-mm cell was used with micromolar concentrations of peptide, and ellipticity was measured over a wavelength range of 180-300 nm. The 1-D NMR studies were conducted on a Varian Unity Plus 500 MHz spectrometer (Varian Associates, Palo Alto, CA). Typically, 128 transients were coadded with a sweep width of 6,000 Hz, an acquisition time of 0.5 s, and a presaturation delay of 1.5 s. Both the presaturation of water and acquisition of data were performed using the transmitter channel. The NMR data were processed with zero filling to 65,536 points and 1 Hz of line broadening using the Varian NMR software.
Radioligand binding. F-12, DMEM, and BSA were purchased from Sigma (St. Louis, MO), fetal bovine serum from Atlanta Biologicals (Atlanta, GA), and geneticin from Calbiochem (La Jolla, CA). CHO-A1 cells containing Y1 receptors (21) were grown in F-12 medium containing 10% fetal bovine serum, 1% streptomycin and penicillin, and 500 µg/ml geneticin; Ngp37 cells containing Y2 receptors (gift of Dr. Anil Rustgi) were grown in DMEM containing 10% fetal bovine serum and 1% streptomycin and penicillin. Both lines were maintained at 37°C and 5% CO2. For binding studies, cells were seeded (50,000 cells/well) in 12-well plates and grown to 90% confluence. Cells were washed once with 1 ml of DMEM containing 25 mM HEPES (pH 7.4) and 10 mM NaHCO3 and were then incubated with the same buffer containing 100 pM 125I-PYY (for description of radiolabel preparation, see Ref. 20) and various concentrations of unlabeled PYY forms. After 1 h at 37°C, plates were washed 4 times with 1 ml ice-cold PBS and the cells were dissolved in 1 ml 0.5 N NaOH. Radioactivity in the lysates was counted in a gamma counter. Saturation binding curves were analyzed at equilibrium to determine concentrations of PYY peptides that inhibited 50% of saturable 125I-PYY binding (IC50). Radioligand equilibrium binding data were fit by nonlinear least-squares regression analysis (LIGAND) to estimate the dissociation constant (Kd) for PYY and the IC50 for the PYY analogs. The inhibition constant (Ki) estimates were calculated with the Cheng and Prusoff equation (10).
Molecular modeling. Model building, molecular dynamics (MD), and energy minimization were performed with Molecular Simulations Insight and Discover modules (MSI, San Diego, CA) on a Silicon Graphics Indigo R4000 UNIX workstation (Mountain View, CA). The MSI cvff force field was used. PYY-(1-36) was assembled stepwise from the NH2 terminus using the primary sequence. The residues 15-36 were then made to adopt a helical conformation, and the backbone dihedral angles around residues 12-14 were adjusted to bring the NH2- and COOH-terminal residues in close proximity (a PP fold). For [Pro34]PYY, the PYY-(1-36) model was used and Glu34 was substituted with a proline residue. For PYY-(3-36), the two NH2-terminal residues were deleted and the backbone dihedral angles of residues 12-14 were adjusted so the NH2 and COOH termini were not in close proximity. These models were then molecule energy minimized via the steepest descent method for 200 iterations, and 1,000 steps of MD at 300 K (1 fs/step) were performed. After the MD was complete, the molecule was again energy minimized for 200 iterations. A distance-dependent dielectric was used to simulate the presence of water, and the charge state of the basic and acidic groups on the peptide were those found at pH 7. The resulting structure was fit with a ribbon representation of the backbone residues to more easily identify structural alterations.
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RESULTS |
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Analytical ultracentrifugation.
Sedimentation equilibrium analyses were performed for PYY,
[Pro34]PYY, and PYY-(3-36).
Monomer-dimer Kd (K = [monomer][monomer]/[dimer]) were found as follows:
PYY, (2.2 ± 0.3) × 102 M;
[Pro34]PYY, (5.7 ± 0.2) × 10
3
M; and PYY-(3-36), (2.0 ± 0.3) × 10
2 M at 21°C, pH 6, and 0.15 M NaCl. Thus all three
forms are present as 80-90% monomers at 1 mM aqueous solution
concentrations. Because the NMR and CD studies of PYY and PYY analogs
described below were performed under similar solution conditions, the
major contributor to spectra was the monomeric form.
CD data.
The CD molecular ellipticities at particular wavelengths can be used to
calculate the percentage of the total number of residues of a peptide
in helical, -sheet, and random coil conformations (9).
The specific sequence of residues involved in these secondary structures cannot be established by this method. Peptide amino acids
arranged in these conformations differentially absorb right- and
left-handed circularly polarized light (expressed as ellipticity) at
characteristic wavelengths (e.g., an
-helix has a
positive peak at +195 nm and negative peaks at
208 and
222 nm). If
more than one conformation is present, the spectrum represents a
concentration-weighted average of the various bands.
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NMR data.
1-D 1H-NMR data were used to verify that PYY,
[Pro34]PYY, and PYY-(3-36) have altered
secondary and tertiary structure. The dispersion of the NMR amide
proton chemical shifts provides information about the chemical
environment of probe nuclei. For example, the amide protons of the
various amino acid types in a random coil conformation (i.e., flexible in solution) have chemical shift values in
the 8.09-8.44 parts per million (ppm) range (30). In
the presence of secondary and tertiary structure, these protons show a
much wider range of chemical shift values. Differences in the line widths and patterns of the amide protons between peptides with nearly
identical sequences also indicate an altered tertiary structure for
these protons (Fig. 3). In this work, the
1H-NMR spectra of the three PYY peptides display different
patterns and a nonrandom-coil-like chemical shift range (7.16-8.72
ppm). The altered amide proton resonance patterns and the range of
amide proton chemical shifts are consistent with the differing
secondary and tertiary structure in PYY, [Pro34]PYY, and
PYY-(3-36) observed in the CD data.
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Binding of PYY analogs to Y1 and Y2
receptors.
The data (Fig. 4A) for
Y1 binding show equivalent displacement of
125I-PYY by PYY and [Pro34]PYY, whereas
PYY-(3-36) was <0.1% as effective as PYY for
displacing label from these receptors. Scatchard analysis yielded a
Kd for PYY of 0.42 nM and
Ki values (calculated from the IC50
values with the Cheng and Prusoff equation) of 0.21 nM for
[Pro34]PYY and 1,050 nM for PYY-(3-36).
For Y2 receptor binding, the data (Fig. 4B) show
nearly equivalent binding for PYY and PYY-(3-36), whereas [Pro34]PYY was <0.01% as efficient in
displacing label. Scatchard analysis indicated a
Kd of 0.03 nM for PYY and
Ki values for [Pro34]PYY of 710 nM
and for PYY-(3-36) of 0.11 nM.
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DISCUSSION |
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The current study provides the first comprehensive analysis of the solution characteristics of PYY, including aggregation, secondary and tertiary structure, and their relationship to receptor binding properties. It is also the first to provide comparative analyses of these factors for PYY itself, the naturally occurring Y2 selective agonist PYY-(3-36), and the synthetic Y1 selective agonist [Pro34]PYY. Our results indicate that there are clear differences in the solution structures of these forms of PYY and in their selectivity for Y1 and Y2 receptors. This provides strong support for the hypothesis that stable tertiary structures of Y receptor agonists in solution are important determinants of their selectivity.
Previous studies on the structure of the related peptide NPY have been hampered by formation of aggregates at the micromolar to millimolar peptide concentrations required for NMR and CD studies. Three NMR studies have shown that NPY exists as a dimer under such conditions (11, 24, 28), a structure unlikely to occur in more physiological settings. Dimer formation thus limits the usefulness of these NPY structure analyses for any attempt to correlate 3-D conformation with biological functions. For PYY and its analogs, our sedimentation equilibrium data indicate that these peptides exist predominantly as monomers under the conditions used in the NMR and CD experiments of this study.
Our receptor binding data confirmed that PYY is a potent agonist at both Y1 and Y2 receptors, whereas [Pro34]PYY and PYY-(3-36) exhibited significantly different binding affinities at these subtypes: the Y1/Y2 selectivity ratio (the ratio of binding affinities at the Y1 and Y2 receptor) was 14 for PYY, 0.0003 for [Pro34]PYY, and 9,500 for PYY-(3-36). These marked differences in selectivity ratios could be caused by altered primary structure (e.g., substitution of proline for Glu34 or deletion of two amino acids) on specific residue-to-residue interactions between ligand and receptor. They could also be caused by changes in secondary and tertiary conformation of the ligand that modify spatial interactions with receptor subtypes. Further studies with analogs designed to have altered structure but minimal alteration in primary structure could substantiate this concept.
We found that the different receptor binding affinities of PYY,
[Pro34]PYY, and PYY-(3-36) were
accompanied by three different percent helicities calculated from CD
data. We found no evidence for the presence of other secondary
structural features (such as -sheets) in any of the PYY forms. It
has been reported that PYY and the Y2-selective agonist
PYY-(13-36) also differ in helical content and
activation of Y2 receptors (22). This group
found the same value for helical content of PYY as reported here and
nearly the same values for the Y2-specific agonist
PYY-(13-36) as we did for
PYY-(3-36). PYY-(3-36) and
PYY-(13-36) are both highly specific Y2
agonists, although they differ markedly in potency. The similarities in
structure (i.e., helicity) of PYY-(3-36) and
PYY-(13-36) suggest an important relationship between
peptide structure and receptor selectivity. Our results also show that
the Y1-selective analog [Pro34]PYY has a
helical content that differs from both PYY and
PYY-(3-36). This finding is also consistent with a
recent report that NPY differs in helicity from
[Pro34]NPY (25).
Further evidence for different tertiary structures in the PYY forms we studied is found in the NMR data. NMR chemical shifts are very sensitive to local changes in secondary and tertiary structure. Although these chemical shifts cannot be reliably translated into tertiary structure, they do provide a qualitative measure of structural alterations. The primary structure of PYY, [Pro34]PYY, and PYY-(3-36) are very similar. If their 3-D conformations were the same, only small changes in the pattern of aromatic and amide proton signals would occur. We observed marked changes in the pattern of these signals (Fig. 3), consistent with significant changes in the tertiary structure of the peptides.
It cannot be directly established from our data whether the observed
differences in secondary and tertiary structures of PYY forms are
responsible for Y receptor subtype selectivity. However, such a
mechanism for the three PYY peptides analyzed here is consistent with
the NMR and CD spectra and receptor binding data. A plausible model to
explain our findings (on the basis of the PP fold structure) is shown
in Fig. 5. In this model, we postulate
that the three analogs exist in three different tertiary structures
produced by their slightly altered primary structures. For PYY, the
structural element that confers its ability to bind to Y1
is the juxtaposition of its NH2 and COOH termini; for
Y2 binding, the selective element is the COOH-terminal
helix. PYY contains both of these structural elements and binds
potently to both receptor subtypes. The proline in
[Pro34]PYY disrupts the COOH-terminal helix, thereby
diminishing the binding to Y2 receptor subtype. The removal
of the NH2-terminal dipeptide from PYY to form
PYY-(3-36) eliminates the juxtaposition of the two
termini, thus reducing binding to the Y1 receptor subtype. This model is supported by similar proposals by others for
Y1- and Y2-selective NPY analogs
(2, 13).
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In summary, a model for the 3-D conformation of PYY and its receptor subtype selective analogs has been generated from direct structural studies of monomeric peptides in solution. This model provides a concrete picture of how subtle changes in the primary amino acid sequences in PYY may result in dramatic alterations in tertiary structure that lead to receptor subtype selectivity.
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ACKNOWLEDGEMENTS |
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This research was supported by CURE Digestive Diseases Research Center Grant DK-41301 and utilized the Peptide Biochemistry and Molecular Probes Core. The research was also supported by the Medical Research Service of the Veterans Health Service and by National Institute of Diabetes and Digestive and Kidney Diseases Grant DK-33850.
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FOOTNOTES |
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Address for reprint requests and other correspondence: J. Reeve, Jr., CURE Digestive Diseases Research Center, Rm. 115, Bld. 115, Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, CA 90073 (E-mail: jreeve{at}ucla.edu).
The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.
Received 5 May 1999; accepted in final form 1 February 2000.
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REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
1.
Adrian, TE,
Savage AP,
Sagor GR,
Allen JM,
Bacarese-Hamilton AJ,
Tatemoto K,
Polak JM,
and
Bloom SR.
Effect of peptide YY on gastric, pancreatic and biliary functions in humans.
Gastroenterology
89:
494-499,
1985[ISI][Medline].
2.
Beck-Sickinger, AG,
and
Jung G.
Structural-activity relationships of neuropeptide Y analogues with respect to Y1 and Y2 receptors.
Biopolymers
37:
123-142,
1995[ISI][Medline].
3.
Beck-Sickinger, AG,
Wieland HA,
Wittneben H,
Willim K,
Rudolf K,
and
Jung G.
Complete L-alanine scan of neuropeptide Y reveals ligand binding to Y1 and Y2 receptors with distinguished conformations.
Eur J Biochem
225:
947-958,
1994[Abstract].
4.
Bilchik, AJ,
Hines OJ,
Adrian TE,
McFadden DW,
Berger JJ,
Zinner MJ,
and
Ashley SW.
Peptide YY is a physiological regulator of water and electrolyte absorption in the canine small bowl in-vivo.
Gastroenterology
105:
1441-1448,
1993[ISI][Medline].
5.
Blomqvist, AG,
and
Herzog H.
Y-receptor subtypeshow many more?
Trends Neurosci
20:
294-298,
1997[ISI][Medline].
6.
Blundell, TL,
Pitts JE,
Tickle SP,
and
Wu CW.
X-ray analysis (1.4 A resolution) of avian pancreatic polypeptide: small globular protein hormone.
Proc Natl Acad Sci USA
78:
4175-4179,
1981[Abstract].
7.
Bottcher, G,
Alumets J,
Hakanson R,
and
Sundler F.
Co-existence of glicentin and peptide YY in colorectal L-cells in cat and man. An electron microscope study.
Regul Pept
13:
283-291,
1986[ISI][Medline].
8.
Chen, CH,
and
Rogers RC.
Central inhibitory action of peptide YY on gastric motility in rats.
Am J Physiol Regulatory Integrative Comp Physiol
269:
R787-R792,
1995
9.
Chen, Y,
Tsang TY,
and
Chau KH.
Determination of the helix and b forms of proteins in aqueous solution by circular dichroism.
Biochemistry
13:
3350-3359,
1974[ISI][Medline].
10.
Cheng, Y,
and
Prusoff WH.
Relationships between the inhibition constant (KI) and the concentrations of inhibitor which causes 50 percent inhibition (IC50) of an enzymatic reaction.
Biochem Pharmacol
22:
3099-3108,
1973[ISI][Medline].
11.
Cowley, DJ,
Hoflack JM,
Pelton JT,
and
Saudek V.
Structure of neuropeptide Y dimer in solution.
Eur J Biochem
205:
1099-1106,
1992[Abstract].
12.
Darbon, H,
Bernassau J,
Deleuz C,
Chenu J,
Roussel A,
and
Cambillau C.
Solution conformation of human neuropeptide Y by 1H nuclear magnetic resonance and restrained molecular dynamics.
Eur J Biochem
209:
765-771,
1992[Abstract].
13.
Fuhlendorff, J,
Johansen NL,
Melberg SG,
Thogersen H,
and
Schwartz TW.
The antiparallel pancreatic polypeptide fold in the binding of neuropeptide Y to Y1 and Y2 receptors.
J Biol Chem
265:
11706-11712,
1990
14.
Glover, ID,
Barlow DJ,
Pitts JE,
Wood SP,
Tickle IJ,
Blundell TL,
Tatemoto K,
Kimmel JR,
Wollmer A,
Strassburger W,
and
Zhang Y.
Conformational studies on the pancreatic polypeptide hormone family.
Eur J Biochem
142:
379-385,
1984[Abstract].
15.
Grandt, D,
Schimiczek M,
Beglinger C,
Layer P,
Goebell H,
Eysselein VE,
and
Reeve JR, Jr.
Two molecular forms of peptide YY (PYY) are abundant in human blood: characterization of a radioimmunoassay recognizing PYY 1-36 and PYY 3-36.
Regul Pept
51:
151-159,
1994[ISI][Medline].
16.
Greeley, GHJ,
Jeng YJ,
Gomez G,
Hashimoto FI,
Hill K,
Kern K,
Kurosky T,
Chuo HF,
and
Thompson JC.
Evidence for regulation of peptide-YY release by the proximal gut.
Endocrinology
124:
1438-1443,
1989[Abstract].
17.
Hu, L,
Balse P,
and
Doughty MB.
Neuropeptide Y N-terminal deletion fragments: correlation between solution structure and receptor binding activity at Y1 receptors in rat brain cortex.
J Med Chem
37:
3622-3629,
1994[ISI][Medline].
18.
Kirby, DA,
Boublik JH,
and
Rivier JE.
Neuropeptide Y: Y1 and Y2 affinities of the complete series of analogues with single D-residue substitutions.
J Med Chem
36:
3802-3808,
1993[ISI][Medline].
19.
Li, X,
Sutcliffe MJ,
Schwartz TW,
and
Dobson CM.
Sequence-specific 1H-NMR assignments and solution structure of bovine pancreatic polypeptide.
Biochemistry
31:
1245-1253,
1992[ISI][Medline].
20.
Mannon, PJ,
Mervin SJ,
and
Sheriff-Carter KD.
Characterization of a Y1-preferring NPY/PYY receptor in HT-29 cells.
Am J Physiol Gastrointest Liver Physiol
267:
G901-G907,
1994
21.
Mannon, PJ,
and
Raymond JR.
The neuropeptide Y/peptide YY Y1 receptor is coupled to MAP kinase via PKC and Ras in CHO cells.
Biochem Biophys Res Commun
246:
91-94,
1998[ISI][Medline].
22.
Minakata, H,
and
Iwashita T.
Synthesis of analogues of peptide YY with modified N-terminal regions: relationships of amphiphilic secondary structures and activity in rat vas deferens.
Biopolymers
29:
61-67,
1990[ISI][Medline].
23.
Minakata, H,
Taylor JW,
Walker MW,
Miller RJ,
and
Kaiser ET.
Characterization of amphiphilic secondary structures in neuropeptide Y through design, synthesis, and study of model peptides.
J Biol Chem
264:
7907-7913,
1989
24.
Monks, SA,
Karagianis G,
Howlett GJ,
and
Norton RS.
Solution structure of human neuropeptide Y.
J Biomol NMR
8:
379-390,
1996[ISI][Medline].
25.
Nordmann, A,
Blommers MJJ,
Fretz H,
Arvinte T,
and
Drake AF.
Aspects of the molecular structure and dynamics of neuropeptide Y.
Eur J Biochem
261:
216-226,
1999
26.
Pappas, TN,
Debas HT,
and
Taylor, II
Enterogastrone-like effect of peptide YY is vagally mediated in the dog.
J Clin Invest
77:
49-53,
1986[ISI][Medline].
27.
Putnam, WS,
Liddle RA,
and
Williams JA.
Inhibitory regulation of rat exocrine pancreas by peptide YY and pancreatic polypeptide.
Am J Physiol Gastrointest Liver Physiol
256:
G698-G703,
1989
28.
Saudek, V,
and
Pelton JT.
Sequence-specific 1H NMR assignment and secondary structure of neuropeptide Y in aqueous solution.
Biochemistry
29:
4509-4515,
1990[ISI][Medline].
29.
Whang, EE,
Hines OJ,
Reeve JR, Jr,
Grandt D,
Moser JA,
Bilchik AJ,
Zinner MJ,
McFadden DW,
and
Ashley SW.
Antisecretory mechanisms of peptide YY in rat distal colon.
Dig Dis Sci
42:
1121-1127,
1997[ISI][Medline].
30.
Wuthrich, K.
NMR of Proteins and Nucleic Acids. New York: Wiley, 1986.