Conformational analysis of a novel cyclic enkephalin analogue using NMR and EDMC calculations (original) (raw)
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Conformational sampling of bioactive conformers: a low-temperature NMR study of15N-Leu–enkephalin
Journal of Peptide Science, 1998
Conformational studies of enkephalins are hampered by their high flexibility which leads to mixtures of quasi-isoenergetic conformers in solution and makes NOEs very difficult to detect in NMR spectra. In order to improve the quality of the NMR data, Leu -enkephalin was synthesized with 15 N-labelled uniformly on all amide nitrogens and examined in a viscous solvent medium at low temperature. HMQC NOESY spectra of the labelled Leu-enkephalin in a DMSO d6 /H 2 O) mixture at 275 K do show numerous NOEs, but these are not consistent with a single conformer and are only sufficient to describe the conformational state as a mixture of several conformers. Here a different approach to the structure -activity relationships of enkephalins is presented: it is possible to analyse the NMR data in terms of limiting canonical structures (i.e. iand k-turns) and finally to select only those consistent with the requirements of l selective agonists and antagonists. This strategy results in the prediction of a family of conformers that may be useful in the design of new l selective opioid peptides.
Conformational studies of diastereomeric cyclic enkephalins by1H-NMR and computer simulations
Biopolymers, 1987
We report the solid-phase synthesis and conformational analysis of a 14-membered, cyclic enkephalin analog, H-Tyr-~$-~-A,bu-Gly-Phe-~-Leu-] (where A,bu represents a,ydiaminobutyric acid). The results from the guinea pig ileum (GPI) and mouse vas deferens (MVD) assays show that the analog, though active, has little seledivity for the p or 8 opioid receptors. Conformational analysis is carried out using 'H-nmr and computer simulations, including molecular dynamics and energy minimizations. The results obtained here are compared with the findings of our studies carried out on the p-receptor-selective diastereomer, Chem. SOC. 101,400&4013]. This comparison allows for insight into the regiospecificity of these cyclic enkephalin analogs. H-Tyr-~[-D-A,b~-Gly-Phe-Leu-] [N. M d , M. H m , and M. Goodman (1985) J. Am.
International Journal of Peptide and Protein Research, 2009
Conformational features of a series of cyclic, penicillamine-containing enkephalin analogs, all of which display selectivity for the delta opioid receptor, were studied by 'H n.m.r. in aqueous solution. Comparison of chemical shifts, coupling constants, and temperature dependence of amide proton chemical shifts suggests different conformational features among the analogs, some of which can be related to the different primary sequences of these peptides. The observation that some of the analogs display disparate individual conformational features while exhibiting similar opioid potency and receptor selectivity suggests that such analogs may share a similar overall topography or at the least maintain the same relative orientations of key portions of the molecule.
International Journal of Peptide and Protein Research, 2009
The solution structures of a series of conformationally restricted pentapeptides with a sequence H-Tyr1-Cys2-Gly3 Phe4-Cys5-OH cyclic (2-5) disulfide, where the cysteines possess either the D or L configuration, were examined by a combined approach including NMR measurements as well as MD calculations. It turned out that at least one low energy conformer of H-Tyr1-Cys2-Gly3-Phe4-Cys5-OH cyclic (2-5) disulfide (DCDCE), as well as one conformer out of the group of calculated conformers for H-Tyr1-D-Cys2-Gly3-Phe4-Cys5-OH cyclic (2-5) disulfide (DCLCE), satisfies the NMR data obtained in this study, whereas for the derivative H-Tyrl-Cys2-Gly3-Phe4-Cys5-OH cyclic (2-5) disulfide, which contains solely L-Cys (LCLCE), there is no single structure compatible with the NMR data. © Munksgaard 1996.
Computer modeling of the solution conformation of cyclic enkephalins
Letters in Peptide Science, 1998
The probable conformations of two cyclic enkephalin analogs, DNS-cyclo[D-Dab-Gly-Trp-Leu] (I) and DNScyclo[D-Dab-Gly-Trp-D-Leu] (II) (DNS = dansyl), were determined by combining the results of NOE, vicinal coupling constant and fluorescence energy transfer measurements with theoretical calculations. The common feature of the conformations for both peptides is the presence of a/~-turn at residues 2 and 3.
The conformation of enkephalin bound to its receptor: an “elusive goal†becoming reality
Frontiers in Molecular Biosciences, 2014
The availability of solid state structures of opioid receptors has prompted us to reconsider a crucial question concerning bioactive peptides: can their conformation be studied without any knowledge of the structure of their receptors? The possibility of giving a meaningful answer to this query rests ultimately on the ease of dealing with the flexibility of bioactive peptides, and amongst them one of the most flexible bioactive peptides, enkephalin. All solution studies of enkephalin hint at an inextricable mixture of quasi isoenergetic conformers. In this study we refer to the only NMR work that yielded inter-residue NOEs, performed at very low temperature. In the present work, we have used the simplest possible docking methods to check the consistency of the main conformers of enkephalin with the steric requirements of the active site of the receptor, as provided by the crystal structure of its complex with naltrindole, a rigid antagonist. We show that the conformers found in the equilibrium mixture at low temperature are indeed compatible with a good fit to the receptor active site. The possible uncertainties linked to the different behavior of agonists and antagonists do not diminish the relevance of the finding.
N -(ureidoethyl)amides of cyclic enkephalin analogs
Journal of Peptide Science, 2009
Novel N-(ureidoethyl)amides of cyclic enkephalin analogs have been synthesized. The p-nitrophenyl carbamate of 1-Boc-1,2-diaminoethane was coupled with 4-methylbenzhydrylamine (MBHA) resin. The Boc group was removed by treatment with HCl/dioxane, and the peptide chain was assembled using Boc strategy. For deprotection of amino function, HCl/dioxane was used. D-Lys or D-Orn were incorporated in position 2, and the side chains of Lys, Orn, Dab, or Dap in position 5 were protected with Fmoc group. Side chain protection was removed by treatment with 55% piperidine in DMF, and cyclization was achieved by treatment with bis-(4-nitrophenyl)carbonate to form a urea bridge. The peptide was cleaved from the resin by treatment with 45% TFA in DCM. The peptides were tested in the guinea-pig ileum (GPI) and mouse vas deferens (MVD) assays. Divers opioid activities were observed, depending on the size of the ring. In comparison with [Leu5]enkephalin, all peptides were more active in the GPI assay (between 125 and 12 times), and some of them were also more potent in the MVD assay. The conformational propensities of each peptide were determined using the EDMC method in conjunction with NMR experiments. This approach allows treating the dynamical behavior of small peptides properly. The results were compared with those obtained previously for corresponding nonsubstituted amides and are in agreement with the biologically active conformation proposed by us earlier. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd.
Solution Conformation of the Synthetic Bovine Proenkephalin-A209-237 by 1H NMR Spectroscopy
Journal of Biological Chemistry, 1998
Proenkephalin-A has been described to generate enkephalins, opoid peptides, and several derived peptides, which display various biological effects, including antinociception and immunological enhancement. Recently, we have isolated from bovine chromaffin granules a new antibacterial peptide, named enkelytin, which corresponds to the bisphosphorylated form of PEAP 209 -237 (Goumon, Y., Strub, J. M., Moniatte, M., Nullans, G., Poteur, L., Hubert, P., Van Dorsselaer, A., Aunis, D., and Metz-Boutigue, M. H. (1996) Eur. J. Biochem. 235, 516 -525). In this paper, the three-dimensional solution structure of synthetic PEAP 209 -237 was investigated by NMR.