Peptides modifiés avec des acides aminés non-naturels comme outils synthétiques pour étudier des interactions protéine-protéine

Ce travail de thèse s inscrit dans l étude des interactions protéines-protéines, en particulier les interactions hormone-récepteur (hormone parathyroïde: hPTH) et antigène-anticorps (pour la Sclérose en Plaques: SEP). Des acides aminés non-naturels portant sur leur chaîne latérale une fonction alcyne ou azide ont été préparés et introduits dans des séquences peptidiques de la PTH-rP, conduisant ensuite par click chemistry à une bibliothèque de cyclopeptides contenant un noyau triazole. Leur étude conformationnelle a été effectuée pour comprendre les analogies existantes avec le modèle cyclopeptidique lactame. D autre part, pour mieux comprendre le mécanisme moléculaire de la reconnaissance anticorpale de la SEP, 2 synthons acides aminés C-glucosylé et N-ribosylé ont été préparés, et introduits dans la structure ß-hairpin de CSF114, dont le laboratoire a démontré précédemment son rôle en tant que sonde N-glucosylée détectant les anticorps dans le sérum des patients affectés par la SEP.During this PhD thesis our attention was focused on protein-protein interactions, in particular on hormone-receptor (for the parathyroid hormone: hPTH) and antigen-antibody interactions (for Multiple Sclerosis: MS). Amino acids bearing on the side chain azide or alkynyl functions were synthesized and introduced in the PTH-rP peptide sequences, to generate via click chemistry a collection of cyclopeptides containing the triazolyl moiety. A conformational study of these cyclopeptides was performed to compare the collection to the parent lactam model. Moreover, to further investigate the molecular mechanism of an antibody-mediated MS, C-glucosylated and N-ribosilated amino acids were synthesized and introduced in the ß-hairpin structure of CSF114, that was demonstrated in our laboratory an efficient N-glucosylated probe detecting antibodies in the MS patients sera.CERGY PONTOISE-BU Neuville (951272102) / SudocSudocFranceF

A hydrophobic disordered peptide spontaneously anchors a covalently bound RNA hairpin to giant lipidic vesicles

International audienceThe attraction of nucleic acids to lipidic compartments is the first step for carriers of potentially inheritable information to self-organise in functionalised synthetic cells. Confocal fluorescence imaging shows that a synthetic amphiphilic peptidyl RNA molecule spontaneously accumulates at the outer bilayer membranes of phospho- and glycolipidic giant vesicles. Cooperatively attractive interactions of −3.4 to −4.0 kcal mol−1 between a random coil hydrophobic peptide and lipid membranes can thus pilot lipophobic RNA to its compartmentation. The separation of mixed lipid phases in the membranes further enhances the local concentration of anchored RNA

CuI-Catalyzed Azideâ Alkyne Intramoleculari-to-(i+4) Side-Chain-to-Side-Chain Cyclization Promotes the Formation of Helix-Like Secondary Structures

Abstract: A solid-phase assembly of model peptides derived from human parathyroid. hormone-related protein (11-19) containing omega-azido- and omega-yl-alpha-amino acid residues in positions i and i+4 was cyclised in solution by an intramolecular Cu-I-catalyzed azide-alkyne 1,3-dipolar Huisgen cycloaddition These series of heterodetic cyclo-nonapeptides varied in the size of the disubstituted 1,2,3-triazolyl-containing bridge, the location and the orientation of the 1,2,3-triazolyl moiety within the bridge The 1,2,3-triazolyl moiety, presented at either 1,4- or 4,1-orientation, is flanked by side chains containing 1-4 CH2 groups that result in bridges comprised from 4-7 CH2 groups connecting residues 13 and 17 Comprehensive conformational analysis employing CD, NMR and molecular dynamics reveals the conformational propensities of these heterodetic cvclo-nonapeptides Cyclo-nonapeptides containing either the 7 methylene bridge (VII and VIII) or the 4 methylene bridge (II) are unstructured in structure-promoting solvent Cyclo-nonapeptide I in which the 1,4-disubstituted 1,2,3-triazolyl is flanked by 3 and 1 CH2 groups in proximity to the respective residues 13 and 17, is stabilized in a non-canonical structure. All the other heterodetic cyclo-nonapeptides (III-VI) in which the 1,2,3-triazolyl is flanked by a total of 5 or 6 CH2 groups nicely accommodate alpha-helical structures and reproduce very closely the helical structure stabilized by the analogous cyclo-nonapeptide in which Lys(13) and Asp(17) are bridged by the isosteric lactam These studies suggest that the bioorthogonal i-to-(i+4) side-chain-to-side-chain cyclization via the prototypic "click reaction" offers a new and powerful approach for generating stable helix mimetic structures