Conformational determinants of agonist versus antagonist properties of [D-Pen2,D-Pen5]enkephalin (DPDPE) analogs at opioid receptors. Comparison of X-ray crystallographic structure, solution 1H NMR data, and molecular dynamic simulations of [L-Ala3]DPDPE and [D-Ala3]DPDPE

Nathan Collins, Judith L. Flippen-Anderson, Ronald C. Haaseth, Jeffery R. Deschamps, Clifford George, K. Kövér, Victor J. Hruby

Research output: Contribution to journalArticle

39 Citations (Scopus)

Abstract

c-[D-Pen2,D-Pen5]enkephalin (DPDPE, 1) is a cyclic, constrained, highly potent, δ opioid receptor selective peptide agonist. Substitution of Gly3 with L-Ala in DPDPE to give [L-Ala3]DPDPE (2) has been shown to produce a peptide with much greater δ receptor binding selectivity than DPDPE itself. However [L-Ala3]DPDPE is only a partial agonist in in vivo antinociception and actually was found to potently antagonize the antinociceptive effects of DPDPE at δ receptors in the brain. In comparison, [D-Ala3]DPDPE (3) is a weak and poorly selective δagonist. In an effort to correlate the biological profiles of these peptides with secondary structure, [L-Ala3]DPDPE and [D-Ala3]-DPDPE were studied by X-ray crystallography and 1H and 13C NMR in DMSO solution. Crystals of both peptides were obtained using vapor diffusion techniques. [L-Ala3]DPDPE crystallizes in the monoclinic space group C2 with cell dimensions a = 36.35(1) Å, b = 19.737(4) Å, c = 28.16(1) Å, β = 129.07(2)°, and V = 15688(9) Å3. The asymmetric unit contains four peptide molecules and approximately 20 water molecules, giving a calculated density of 1.274 g cm-3. The conformation of all four independent [L-Ala3]DPDPE molecules is essentially the same. [D-Ala3]-DPDPE crystallizes in the monoclinic space group P21 with cell dimensions a = 12.271(2) Å, b = 9.600(a) Å, c = 18.750(4) Å, β = 103.56(2)°, and V = 2147.2(7) Å3. The asymmetric unit contains one peptide molecule and 10 molecules of water, giving a calculated density of 1.298 g cm-3. Comparison of these X-ray structures with the crystal structure previously reported for DPDPE indicates that there are differences in the disulfide bond region for all three peptides. ROEs determined about the disulfide regions of 1-3 in solution are indicative of a high degree of conformational interconversion, while heteronuclear coupling constants between the D-Pen2.3 Hα and Cγ,γ + ′ carbons indicate a strong preference for a gauche (+) χ1 angle in 2. The backbone conformations of DPDPE and [D-Ala3]-DPDPE in the X-ray structures are virtually identical, while in [L-Ala3]DPDPE, there is a rotation of approximately 160° about both ψ2 and φ3 compared to DPDPE which has the effect of rotating this amide group approximately 180° relative to DPDPE. The solution NMR data for the peptide backbone conformations of 2 and 3 are mainly consistent with their X-ray structures. However, MD simulation of all three compounds, starting with the geometries of their X-ray structures, indicates that by comparison of observed and predicted ROE intensities an equilibrium between these conformations is likely in solution. The "DPDPE-like" conformation for [L-Ala3]DPDPE is however significantly higher in energy than the X-ray structure reported here and, thus, is predicted to be less populated in solution and in receptor binding. It is concluded that the X-ray structure of DPDPE represents an agonist conformation for this peptide at the δ opioid receptor and that the corresponding X-ray structure of [L-Ala3]DPDPE represents an antagonist conformation due to the differences in conformation between positions 2 and 3. Considerations on the structural implications of this conformational difference on receptor binding are discussed.

Original languageEnglish
Pages (from-to)2143-2152
Number of pages10
JournalJournal of the American Chemical Society
Volume118
Issue number9
Publication statusPublished - 1996

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D-Penicillamine (2,5)-Enkephalin
Opioid Receptors
Molecular Dynamics Simulation
Peptides
Molecular dynamics
Conformations
Nuclear magnetic resonance
X-Rays
X rays
Computer simulation
Molecules
Proton Magnetic Resonance Spectroscopy
X ray crystallography
Amides
Water
Brain
Substitution reactions
Crystal structure
Disulfides
Vapors

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Conformational determinants of agonist versus antagonist properties of [D-Pen2,D-Pen5]enkephalin (DPDPE) analogs at opioid receptors. Comparison of X-ray crystallographic structure, solution 1H NMR data, and molecular dynamic simulations of [L-Ala3]DPDPE and [D-Ala3]DPDPE. / Collins, Nathan; Flippen-Anderson, Judith L.; Haaseth, Ronald C.; Deschamps, Jeffery R.; George, Clifford; Kövér, K.; Hruby, Victor J.

In: Journal of the American Chemical Society, Vol. 118, No. 9, 1996, p. 2143-2152.

Research output: Contribution to journalArticle

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title = "Conformational determinants of agonist versus antagonist properties of [D-Pen2,D-Pen5]enkephalin (DPDPE) analogs at opioid receptors. Comparison of X-ray crystallographic structure, solution 1H NMR data, and molecular dynamic simulations of [L-Ala3]DPDPE and [D-Ala3]DPDPE",
abstract = "c-[D-Pen2,D-Pen5]enkephalin (DPDPE, 1) is a cyclic, constrained, highly potent, δ opioid receptor selective peptide agonist. Substitution of Gly3 with L-Ala in DPDPE to give [L-Ala3]DPDPE (2) has been shown to produce a peptide with much greater δ receptor binding selectivity than DPDPE itself. However [L-Ala3]DPDPE is only a partial agonist in in vivo antinociception and actually was found to potently antagonize the antinociceptive effects of DPDPE at δ receptors in the brain. In comparison, [D-Ala3]DPDPE (3) is a weak and poorly selective δagonist. In an effort to correlate the biological profiles of these peptides with secondary structure, [L-Ala3]DPDPE and [D-Ala3]-DPDPE were studied by X-ray crystallography and 1H and 13C NMR in DMSO solution. Crystals of both peptides were obtained using vapor diffusion techniques. [L-Ala3]DPDPE crystallizes in the monoclinic space group C2 with cell dimensions a = 36.35(1) {\AA}, b = 19.737(4) {\AA}, c = 28.16(1) {\AA}, β = 129.07(2)°, and V = 15688(9) {\AA}3. The asymmetric unit contains four peptide molecules and approximately 20 water molecules, giving a calculated density of 1.274 g cm-3. The conformation of all four independent [L-Ala3]DPDPE molecules is essentially the same. [D-Ala3]-DPDPE crystallizes in the monoclinic space group P21 with cell dimensions a = 12.271(2) {\AA}, b = 9.600(a) {\AA}, c = 18.750(4) {\AA}, β = 103.56(2)°, and V = 2147.2(7) {\AA}3. The asymmetric unit contains one peptide molecule and 10 molecules of water, giving a calculated density of 1.298 g cm-3. Comparison of these X-ray structures with the crystal structure previously reported for DPDPE indicates that there are differences in the disulfide bond region for all three peptides. ROEs determined about the disulfide regions of 1-3 in solution are indicative of a high degree of conformational interconversion, while heteronuclear coupling constants between the D-Pen2.3 Hα and Cγ,γ + ′ carbons indicate a strong preference for a gauche (+) χ1 angle in 2. The backbone conformations of DPDPE and [D-Ala3]-DPDPE in the X-ray structures are virtually identical, while in [L-Ala3]DPDPE, there is a rotation of approximately 160° about both ψ2 and φ3 compared to DPDPE which has the effect of rotating this amide group approximately 180° relative to DPDPE. The solution NMR data for the peptide backbone conformations of 2 and 3 are mainly consistent with their X-ray structures. However, MD simulation of all three compounds, starting with the geometries of their X-ray structures, indicates that by comparison of observed and predicted ROE intensities an equilibrium between these conformations is likely in solution. The {"}DPDPE-like{"} conformation for [L-Ala3]DPDPE is however significantly higher in energy than the X-ray structure reported here and, thus, is predicted to be less populated in solution and in receptor binding. It is concluded that the X-ray structure of DPDPE represents an agonist conformation for this peptide at the δ opioid receptor and that the corresponding X-ray structure of [L-Ala3]DPDPE represents an antagonist conformation due to the differences in conformation between positions 2 and 3. Considerations on the structural implications of this conformational difference on receptor binding are discussed.",
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T1 - Conformational determinants of agonist versus antagonist properties of [D-Pen2,D-Pen5]enkephalin (DPDPE) analogs at opioid receptors. Comparison of X-ray crystallographic structure, solution 1H NMR data, and molecular dynamic simulations of [L-Ala3]DPDPE and [D-Ala3]DPDPE

AU - Collins, Nathan

AU - Flippen-Anderson, Judith L.

AU - Haaseth, Ronald C.

AU - Deschamps, Jeffery R.

AU - George, Clifford

AU - Kövér, K.

AU - Hruby, Victor J.

PY - 1996

Y1 - 1996

N2 - c-[D-Pen2,D-Pen5]enkephalin (DPDPE, 1) is a cyclic, constrained, highly potent, δ opioid receptor selective peptide agonist. Substitution of Gly3 with L-Ala in DPDPE to give [L-Ala3]DPDPE (2) has been shown to produce a peptide with much greater δ receptor binding selectivity than DPDPE itself. However [L-Ala3]DPDPE is only a partial agonist in in vivo antinociception and actually was found to potently antagonize the antinociceptive effects of DPDPE at δ receptors in the brain. In comparison, [D-Ala3]DPDPE (3) is a weak and poorly selective δagonist. In an effort to correlate the biological profiles of these peptides with secondary structure, [L-Ala3]DPDPE and [D-Ala3]-DPDPE were studied by X-ray crystallography and 1H and 13C NMR in DMSO solution. Crystals of both peptides were obtained using vapor diffusion techniques. [L-Ala3]DPDPE crystallizes in the monoclinic space group C2 with cell dimensions a = 36.35(1) Å, b = 19.737(4) Å, c = 28.16(1) Å, β = 129.07(2)°, and V = 15688(9) Å3. The asymmetric unit contains four peptide molecules and approximately 20 water molecules, giving a calculated density of 1.274 g cm-3. The conformation of all four independent [L-Ala3]DPDPE molecules is essentially the same. [D-Ala3]-DPDPE crystallizes in the monoclinic space group P21 with cell dimensions a = 12.271(2) Å, b = 9.600(a) Å, c = 18.750(4) Å, β = 103.56(2)°, and V = 2147.2(7) Å3. The asymmetric unit contains one peptide molecule and 10 molecules of water, giving a calculated density of 1.298 g cm-3. Comparison of these X-ray structures with the crystal structure previously reported for DPDPE indicates that there are differences in the disulfide bond region for all three peptides. ROEs determined about the disulfide regions of 1-3 in solution are indicative of a high degree of conformational interconversion, while heteronuclear coupling constants between the D-Pen2.3 Hα and Cγ,γ + ′ carbons indicate a strong preference for a gauche (+) χ1 angle in 2. The backbone conformations of DPDPE and [D-Ala3]-DPDPE in the X-ray structures are virtually identical, while in [L-Ala3]DPDPE, there is a rotation of approximately 160° about both ψ2 and φ3 compared to DPDPE which has the effect of rotating this amide group approximately 180° relative to DPDPE. The solution NMR data for the peptide backbone conformations of 2 and 3 are mainly consistent with their X-ray structures. However, MD simulation of all three compounds, starting with the geometries of their X-ray structures, indicates that by comparison of observed and predicted ROE intensities an equilibrium between these conformations is likely in solution. The "DPDPE-like" conformation for [L-Ala3]DPDPE is however significantly higher in energy than the X-ray structure reported here and, thus, is predicted to be less populated in solution and in receptor binding. It is concluded that the X-ray structure of DPDPE represents an agonist conformation for this peptide at the δ opioid receptor and that the corresponding X-ray structure of [L-Ala3]DPDPE represents an antagonist conformation due to the differences in conformation between positions 2 and 3. Considerations on the structural implications of this conformational difference on receptor binding are discussed.

AB - c-[D-Pen2,D-Pen5]enkephalin (DPDPE, 1) is a cyclic, constrained, highly potent, δ opioid receptor selective peptide agonist. Substitution of Gly3 with L-Ala in DPDPE to give [L-Ala3]DPDPE (2) has been shown to produce a peptide with much greater δ receptor binding selectivity than DPDPE itself. However [L-Ala3]DPDPE is only a partial agonist in in vivo antinociception and actually was found to potently antagonize the antinociceptive effects of DPDPE at δ receptors in the brain. In comparison, [D-Ala3]DPDPE (3) is a weak and poorly selective δagonist. In an effort to correlate the biological profiles of these peptides with secondary structure, [L-Ala3]DPDPE and [D-Ala3]-DPDPE were studied by X-ray crystallography and 1H and 13C NMR in DMSO solution. Crystals of both peptides were obtained using vapor diffusion techniques. [L-Ala3]DPDPE crystallizes in the monoclinic space group C2 with cell dimensions a = 36.35(1) Å, b = 19.737(4) Å, c = 28.16(1) Å, β = 129.07(2)°, and V = 15688(9) Å3. The asymmetric unit contains four peptide molecules and approximately 20 water molecules, giving a calculated density of 1.274 g cm-3. The conformation of all four independent [L-Ala3]DPDPE molecules is essentially the same. [D-Ala3]-DPDPE crystallizes in the monoclinic space group P21 with cell dimensions a = 12.271(2) Å, b = 9.600(a) Å, c = 18.750(4) Å, β = 103.56(2)°, and V = 2147.2(7) Å3. The asymmetric unit contains one peptide molecule and 10 molecules of water, giving a calculated density of 1.298 g cm-3. Comparison of these X-ray structures with the crystal structure previously reported for DPDPE indicates that there are differences in the disulfide bond region for all three peptides. ROEs determined about the disulfide regions of 1-3 in solution are indicative of a high degree of conformational interconversion, while heteronuclear coupling constants between the D-Pen2.3 Hα and Cγ,γ + ′ carbons indicate a strong preference for a gauche (+) χ1 angle in 2. The backbone conformations of DPDPE and [D-Ala3]-DPDPE in the X-ray structures are virtually identical, while in [L-Ala3]DPDPE, there is a rotation of approximately 160° about both ψ2 and φ3 compared to DPDPE which has the effect of rotating this amide group approximately 180° relative to DPDPE. The solution NMR data for the peptide backbone conformations of 2 and 3 are mainly consistent with their X-ray structures. However, MD simulation of all three compounds, starting with the geometries of their X-ray structures, indicates that by comparison of observed and predicted ROE intensities an equilibrium between these conformations is likely in solution. The "DPDPE-like" conformation for [L-Ala3]DPDPE is however significantly higher in energy than the X-ray structure reported here and, thus, is predicted to be less populated in solution and in receptor binding. It is concluded that the X-ray structure of DPDPE represents an agonist conformation for this peptide at the δ opioid receptor and that the corresponding X-ray structure of [L-Ala3]DPDPE represents an antagonist conformation due to the differences in conformation between positions 2 and 3. Considerations on the structural implications of this conformational difference on receptor binding are discussed.

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