Influence of pH on indole-dependent heterodimeric interactions between Anopheles gambiae odorant-binding proteins OBP1 and OBP4.

Insect Odorant Binding Proteins (OBPs) constitute important components of their olfactory apparatus, as they are essential for odor recognition. OBPs undergo conformational changes upon pH change, altering their interactions with odorants. Moreover, they can form heterodimers with novel binding characteristics.

2D finger-printing and molecular docking studies identified potent mosquito repellents targeting odorant binding protein 1.

Personal protection measures against the mosquitoes like the use of repellents constitute valuable tools in the effort to prevent the transmission of vector-borne diseases. Therefore, the discovery of novel repellent molecules which will be effective at lower concentrations and provide a longer duration of protection remains an urgent need. Mosquito Odorant-Binding Proteins (OBPs) involved in the initial steps of the olfactory signal transduction cascade have been recognized not only as passive carriers of odors and pheromones but also as the first molecular filter to discriminate semiochemicals, hence serving as molecular targets for the design of novel pest control agents.

The structure of AgamOBP5 in complex with the natural insect repellents Carvacrol and Thymol: Crystallographic, fluorescence and thermodynamic binding studies.

Among several proteins participating in the olfactory perception process of insects, Odorant Binding Proteins (OBPs) are today considered valid targets for the discovery of compounds that interfere with their host-detection behavior. The 3D structures of Anopheles gambiae mosquito AgamOBP1 in complex with the known synthetic repellents DEET and Icaridin have provided valuable information on the structural characteristics that govern their selective binding. However, no structure of a plant-derived repellent bound to an OBP has been available until now.

A Combined Computational Methodology for the Discovery of Hit Compounds with Putative Insect Repellency Properties.

Mosquitoes and other hematophagous arthropods, the primary vectors of multiple parasites and viruses, are responsible for the transmission of serious diseases to humans. Nowadays, the interest is focused on the development of novel repellents to the existing ones with advanced properties. The present study attempts the discovery of novel hit compounds which may evolve as insect repellents using a combined computational methodology targeting the Odorant Binding Protein 1 (OBP1).

Identification of novel bioinspired synthetic mosquito repellents by combined ligand-based screening and OBP-structure-based molecular docking.

In this work we report a fast and efficient virtual screening protocol for discovery of novel bioinspired synthetic mosquito repellents with lower volatility and, in all likelihood, increased protection time as compared with their plant-derived parental compounds. Our screening protocol comprises two filtering steps. The first filter is based on the shape and chemical similarity to known plant-derived repellents, whereas the second filter is based on the predicted similarity of the ligand's binding mode to the Anopheles gambiae odorant binding protein (AgamOBP1) relative to that of DEET and Icaridin to the same OBP.

The crystal structure of the AgamOBP1•Icaridin complex reveals alternative binding modes and stereo-selective repellent recognition.

Anopheles gambiae Odorant Binding Protein 1 in complex with the most widely used insect repellent DEET, was the first reported crystal structure of an olfactory macromolecule with a repellent, and paved the way for OBP1-structure-based approaches for discovery of new host-seeking disruptors. In this work, we performed STD-NMR experiments to directly monitor and verify the formation of a complex between AgamOBP1 and Icaridin, an efficient DEET alternative. Furthermore, Isothermal Titration Calorimetry experiments provided evidence for two Icaridin-binding sites with different affinities (Kd = 0.

Crystal and solution studies of the "Plus-C" odorant-binding protein 48 from Anopheles gambiae: control of binding specificity through three-dimensional domain swapping.

Much physiological and behavioral evidence has been provided suggesting that insect odorant-binding proteins (OBPs) are indispensable for odorant recognition and thus are appealing targets for structure-based discovery and design of novel host-seeking disruptors. Despite the fact that more than 60 putative OBP-encoding genes have been identified in the malaria vector Anopheles gambiae, the crystal structures of only six of them are known. It is therefore clear that OBP structure determination constitutes the bottleneck for structure-based approaches to mosquito repellent/attractant discovery.

Sourcing the affinity of flavonoids for the glycogen phosphorylase inhibitor site via crystallography, kinetics and QM/MM-PBSA binding studies: comparison of chrysin and flavopiridol.

Flavonoids have been discovered as novel inhibitors of glycogen phosphorylase (GP), a target to control hyperglycemia in type 2 diabetes. To elucidate the mechanism of inhibition, we have determined the crystal structure of the GPb-chrysin complex at 1.9 Å resolution.

Anopheles gambiae odorant binding protein crystal complex with the synthetic repellent DEET: implications for structure-based design of novel mosquito repellents.

Insect odorant binding proteins (OBPs) are the first components of the olfactory system to encounter and bind attractant and repellent odors emanating from various sources for presentation to olfactory receptors, which trigger relevant signal transduction cascades culminating in specific physiological and behavioral responses. For disease vectors, particularly hematophagous mosquitoes, repellents represent important defenses against parasitic diseases because they effect a reduction in the rate of contact between the vectors and humans. OBPs are targets for structure-based rational approaches for the discovery of new repellent or other olfaction inhibitory compounds with desirable features.

Kinetic and crystallographic studies of glucopyranose spirohydantoin and glucopyranosylamine analogs inhibitors of glycogen phosphorylase.

Glycogen phosphorylase (GP) is currently exploited as a target for inhibition of hepatic glycogenolysis under high glucose conditions. Spirohydantoin of glucopyranose and N-acetyl-beta-D-glucopyranosylamine have been identified as the most potent inhibitors of GP that bind at the catalytic site. Four spirohydantoin and three beta-D-glucopyranosylamine analogs have been designed, synthesized and tested for inhibition of GP in kinetic experiments.

Structural basis of the synergistic inhibition of glycogen phosphorylase a by caffeine and a potential antidiabetic drug.

Caffeine, an allosteric inhibitor of glycogen phosphorylase a (GPa), has been shown to act synergistically with the potential antidiabetic drug (-)(S)-3-isopropyl 4-(2-chlorophenyl)-1,4-dihydro-1-ethyl-2-methyl-pyridine-3,5,6-tricarboxylate (W1807). The structure of GPa complexed with caffeine and W1807 has been determined at 100K to 2.3 A resolution, and refined to a crystallographic R value of 0.

Flavopiridol inhibits glycogen phosphorylase by binding at the inhibitor site.

Flavopiridol (L86-8275) ((-)-cis-5, 7-dihydroxy-2-(2-chlorophenyl)-8-[4-(3-hydroxy-1-methyl)-piperidinyl] -4H-benzopyran-4-one), a potential antitumor drug, currently in phase II trials, has been shown to be an inhibitor of muscle glycogen phosphorylase (GP) and to cause glycogen accumulation in A549 non-small cell lung carcinoma cells (Kaiser, A., Nishi, K., Gorin, F.

A new allosteric site in glycogen phosphorylase b as a target for drug interactions.

Background: In muscle and liver, glycogen concentrations are regulated by the coordinated activities of glycogen phosphorylase (GP) and glycogen synthase. GP exists in two forms: the dephosphorylated low-activity form GPb and the phosphorylated high-activity form GPa. In both forms, allosteric effectors can promote equilibrium between a less active T state and a more active R state.

Allosteric inhibition of glycogen phosphorylase a by the potential antidiabetic drug 3-isopropyl 4-(2-chlorophenyl)-1,4-dihydro-1-ethyl-2-methyl-pyridine-3,5,6-tricarbo xylate.

The effect of the potential antidiabetic drug (-)(S)-3-isopropyl 4-(2-chlorophenyl)-1,4-dihydro-1-ethyl-2-methyl-pyridine-3,5,6-tricarbox ylate (W1807) on the catalytic and structural properties of glycogen phosphorylase a has been studied. Glycogen phosphorylase (GP) is an allosteric enzyme whose activity is primarily controlled by reversible phosphorylation of Ser14 of the dephosphorylated enzyme (GPb, less active, predominantly T-state) to form the phosphorylated enzyme (GPa, more active, predominantly R-state). Upon conversion of GPb to GPa, the N-terminal tail (residues 5-22), which carries the Ser14(P), changes its conformation into a distorted 3(10) helix and its contacts from intrasubunit to intersubunit.

Effects of commonly used cryoprotectants on glycogen phosphorylase activity and structure.

The effects of a number of cryoprotectants on the kinetic and structural properties of glycogen phosphorylase b have been investigated. Kinetic studies showed that glycerol, one of the most commonly used cryoprotectants in X-ray crystallographic studies, is a competitive inhibitor with respect to substrate glucose-1-P with an apparent Ki value of 3.8% (v/v).

The structure of glycogen phosphorylase b with an alkyldihydropyridine-dicarboxylic acid compound, a novel and potent inhibitor.

Background: In muscle and liver, glycogen concentrations are regulated by the reciprocal activities of glycogen phosphorylase (GP) and glycogen synthase. An alkyl-dihydropyridine-dicarboxylic acid has been found to be a potent inhibitor of GP, and as such has potential to contribute to the regulation of glycogen metabolism in the non-insulin-dependent diabetes diseased state. The inhibitor has no structural similarity to the natural regulators of GP.

Activator anion binding site in pyridoxal phosphorylase b: the binding of phosphite, phosphate, and fluorophosphate in the crystal.

It has been established that phosphate analogues can activate glycogen phosphorylase reconstituted with pyridoxal in place of the natural cofactor pyridoxal 5'-phosphate (Change YC. McCalmont T, Graves DJ. 1983.