Papers by Laurence Miguet
Journal of Receptors and Signal Transduction, 2006
Phenylthiocarbamide tastes intensely bitter to some individuals, but others find it completely ta... more Phenylthiocarbamide tastes intensely bitter to some individuals, but others find it completely tasteless. Recently, it was suggested that phenylthiocarbamide elicits bitter taste by interacting with a human G protein-coupled receptor (hTAS2R38) encoded by the PTC gene. The phenylthiocarbamide nontaster trait was linked to three single nucleotide polymorphisms occurring in the PTC gene. Using the crystal structure of bovine rhodopsin as template, we generated the 3D structure of hTAS2R38 bitter taste receptor. We were able to map on the receptor structure the amino acids affected by the genetic polymorphisms and to propose molecular functions for two of them that explained the emergence of the nontaster trait. We used molecular docking simulations to find that phenylthiocarbamide exhibited a higher affinity for the target receptor than the structurally similar molecule 6-n-propylthiouracil, in line with recent experimental studies. A 3D model was constructed for the hTAS2R16 bitter taste receptor as well, by applying the same protocol. We found that the recently published experimental ligand binding affinity data for this receptor correlated well with the binding scores obtained from our molecular docking calculations.
Journal of Medicinal Chemistry, 2009
Penicillin binding proteins (PBPs) are involved in the biosynthesis of the peptidoglycan layer co... more Penicillin binding proteins (PBPs) are involved in the biosynthesis of the peptidoglycan layer constitutive of the bacterial envelope. They have been targeted for more than half a century by extensively derived molecular scaffolds of penicillins and cephalosporins. Streptococcus pneumoniae resists the antibiotic pressure by inducing highly mutated PBPs that can no longer bind the β-lactam containing agents. To find inhibitors of PBP2x from Streptococcus pneumoniae (spPBP2x) with novel chemical scaffold so as to circumvent the resistance problems, a hierarchical virtual screening procedure was performed on the NCI database containing approximately 260000 compounds. The calculations involved ligand-based pharmacophore mapping studies and molecular docking simulations in a homology model of spPBP2x from the highly resistant strain 5204. A total of 160 hits were found, and 55 were available for experimental tests. Three compounds harboring two novel chemical scaffolds were identified as inhibitors of the resistant strain 5204-spPBP2x at the micromolar range. a Abbreviations: spPBP2x, penicillin Binding Protein 2x from Streptococcus pneumoniae; R6-PBP2x, 5204-PBP2x, sp328-PBP2x, PBP2x of Streptococcus pneumonia from respectively from the sensitive R6 strain and the resistant 5204 and 328 strains; NAG, N-acetylglucosamine; NAM, N-acetylmuramic acid; ASPRE, active-site penicillin recognizing enzymes; RA, residual activity; BSA, bovine serum albumin; S2d, Nbenzoyl-D-alanyl-thioglycolate; LTV, lactivicin; PLTV, phenoxyacetyllactivicin; CPH, common pharmacophore hypotheses.
Journal of Computer-Aided Molecular Design, 2006
Human 11b-hydroxysteroid dehydrogenase type 1 (11bHSD1) catalyzes the interconversion of cortison... more Human 11b-hydroxysteroid dehydrogenase type 1 (11bHSD1) catalyzes the interconversion of cortisone into active cortisol. 11bHSD1 inhibition is a tempting target for the treatment of a host of human disorders that might benefit from blockade of glucocorticoid action, such as obesity, metabolic syndrome, and diabetes type 2. Here, we report an in silico screening study aimed at identifying new selective inhibitors of human 11bHSD1 enzyme. In the first step, homology modeling was employed to build the 3D structure of 11bHSD1. Further, molecular docking was used to validate the predicted model by showing that it was able to discriminate between known 11bHSD1 inhibitors or substrates and non-inhibitors. The homology model was found to reproduce closely the crystal structure that became publicly available in the final stages of this work. Finally, we carried out structure-based virtual screening experiments on both the homology model and the crystallographic structure with a database of 114Õ000 natural molecules. Among these, 15 molecules were consistently selected as inhibitors based on both the model and crystal structures of the enzyme, implying a good quality for the homology model. Among these putative 11bHSD1 inhibitors, two were flavonone derivatives that have already been shown to be potent inhibitors of the enzyme.
Journal of Biological Chemistry, 2008
Codakine is an abundant 14-kDa mannose-binding C-type lectin isolated from the gills of the sea b... more Codakine is an abundant 14-kDa mannose-binding C-type lectin isolated from the gills of the sea bivalve Codakia orbicularis. Binding studies using inhibition of hemagglutination indicated specificity for mannose and fucose monosaccharides. Further experiments using a glycan array demonstrated, however, a very fine specificity for N-linked biantennary complex-type glycans. An unusually high affinity was measured by titration microcalorimetry performed with a biantennary Asn-linked nonasaccharide. The crystal structure of the native lectin at 1.3 Å resolution revealed a new type of disulfide-bridged homodimer. Each monomer displays three intramolecular disulfide bridges and contains only one calcium ion located in the canonical binding site that is occupied by a glycerol molecule. The structure of the complex between Asn-linked nonasaccharide and codakine has been solved at 1.7 Å resolution. All residues could be located in the electron density map, except for the capping 1-4-linked galactosides. The ␣1-6-linked mannose binds to calcium by coordinating the O3 and O4 hydroxyl groups. The GlcNAc moiety of the ␣1,6 arm engages in several hydrogen bonds with the protein, whereas the Glc-NAc on the other antenna is stacked against Trp 108 , forming an extended binding site. This is the first structural report for a bivalve lectin.
Drug Metabolism and Disposition, 2007
The exporter ABCC2 (cMOAT, MRP2) is a membrane-bound protein on the apical side of enterocytes an... more The exporter ABCC2 (cMOAT, MRP2) is a membrane-bound protein on the apical side of enterocytes and hepatic biliary vessels that transports leukotriene C(4), glutathione, some conjugated bile salts, drugs, xenobiotics, and phytonutrients. The latter class includes quercetin, a bioactive flavonoid found in foods such as onions, apples, tea, and wine. There is no available three-dimensional (3D) structure of ABCC2. We have predicted the 3D structure by in silico modeling, showing that 3-[[3-[2-(7-chloroquinolin-2-yl)vinyl]phenyl]-(2-dimethylcarbamoylethylsulfanyl)methylsulfanyl] propionic acid (MK571) binds most tightly to the putative binding site, and then tested the computational prediction experimentally by measuring interaction with all quercetin monoglucuronides occurring in vivo (quercetin substituted with glucuronic acid at the 3-, 3'-, 4'-, and 7-hydroxyl groups). The 4'-O-beta-D-glucuronide is predicted in silico to interact most strongly and the 3-O-beta-D-glucuronide most weakly, and this prediction is supported experimentally using binding and competition assays on ABCC2-overexpressing baculovirus-infected Sf9 cells. To test the transport in situ, we examined the effect of two ABCC2 inhibitors, MK571 and cyclosporin A, on the transport into the media of quercetin glucuronides produced intracellularly by Caco2 cells. The inhibitors reduced the amount of all quercetin glucuronides in the media. The results show that the molecular model of ABCC2 agrees well with experimentally determined ABCC2-ligand interactions and, importantly, that the interaction of ABCC2 with quercetin glucuronides is dependent on the position and nature of substitution.
Biochemical Pharmacology, 2009
Journal of Cheminformatics, 2009
Background: Detailed experimental three dimensional structures of carbohydrates are often difficu... more Background: Detailed experimental three dimensional structures of carbohydrates are often difficult to acquire. Molecular modelling and computational conformation prediction are therefore commonly used tools for three dimensional structure studies. Modelling procedures generally require significant training and computing resources, which is often impractical for most experimental chemists and biologists. Shape has been developed to improve the availability of modelling in this field.
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Papers by Laurence Miguet