Crystal structures and binding dynamics of Odorant-Binding Protein 3 from two aphid species Megoura viciae and Nasonovia ribisnigri

Aphids use chemical cues to locate hosts and find mates. The vetch aphid Megoura viciae feeds exclusively on the Fabaceae, whereas the currant-lettuce aphid Nasonovia ribisnigri alternates hosts between the Grossulariaceae and Asteraceae. Both species use alarm pheromones to warn of dangers. For N. ribisnigri this pheromone is a single component (E)-β-farnesene but M. viciae uses a mixture of (E)-β-farnesene, (-)-α- pinene, β-pinene, and limonene. Odorant-binding proteins (OBP) are believed to capture and transport such semiochemicals to their receptors. Here, we report the first aphid OBP crystal structures and examine their molecular interactions with the alarm pheromone components. Our study reveals some unique structural features: 1) the lack of internal ligand binding site; 2) a striking groove in the surface of the proteins as a putative binding site; 3) the N-terminus rather than the C-terminus occupies the site closing off the conventional OBP pocket. The results from fluorescent binding assays, molecular docking and dynamics demonstrate that OBP3 from M. viciae can bind to all four alarm pheromone components and the differential ligand binding between these very similar OBP3s from the two aphid species is determined mainly by the direct π-π interactions between ligands and the aromatic residues of OBP3s in the binding pocket

Glucopyranose spirohydantoins: Specific inhibitors of glycogen phosphorylase

A short synthesis of the spirohydantoin of glucopyranose 1β [a potent and specific inhibitor of glycogen phosphorylase], together with its inactive anomer 1α, from a readily available heptonolactone is described; this is the first synthesis of a spirohydantoin of a pyranose in which the pyranose ring is formed after the hydantoin ring

A galactopyranose analogue of hydantocidin

The synthesis of (2R,3R,4S,5R,6S)-3,4,5-trihydroxy-2-hydroxymethyl-7,9-diaza-oxaspiro-[ 4,5]decane-8,10-dione, a galactopyranose analogue of the powerful herbicide hydantocidin, is described. The compound caused no inhibition of the activity of a number of glucosyl or galactosyl transferases, or of α- or β-galactosidases. An azidoester containing a galactopyranosyl moiety may be a useful intermediate for the generation of libraries of compounds of galactose mimics

Triazole carboxylic acids as anionic sugar mimics? Inhibition of glycogen phosphorylase by a D-glucotriazole carboxylate

Triazole-carboxylic acids related to D-glucose and D-galactose may be prepared by intramolecular [1,3]-dipolar cycloadditions of azides to unsaturated esters, followed by bromine oxidation of the resulting triazoline. Such materials may provide a series of anionic mimics of carbohydrates

Glucofuranose analogues of hydantocidin

Epimeric spirohydantoins of glucofuranose, analogues of hydantocidin, are readily prepared from glucoheptonolactone. No rearrangement of spirohydantoins of glucofuranose to pyranose isomers was observed; a novel rearrangement was observed of a glucofuranose spirohydantoin to an isomeric oxazolidinone, (3aR,4'R,5S,6S,6aR)-5-(2',2'-dimethyl-1',3'-dioxolane-4'-yl)-6-hydroxy -3a-N-phenylcarboxamido-tetrahydrofuro[2.3-d]-1,2-oxazolidine-2-one, the structure of which was established by X-ray crystallographic analysis. The X-ray crystal structure of (1'R,2R,3R,4R,5R)-6,8-diaza-3,4-dihydroxy-2-(1',2'-dihydroxyethyl)-1-o xa-8-N-phenyl spiro[4.4]nonane-7,9-dione is reported