Polyoxometalate HIV-1 protease inhibitors. A new mode of protease inhibition

Molecular simulation study of the binding mechanism of [α-PTi2W10O40]7- for its promising broad-spectrum inhibitory activity to FluV-A neuraminidase

Polyoxometalate (POM) has promising antiviral activities. It shows broad-spectrum inhibiting ability, high efficiency, and low toxicity. Experimental assays show that titanium containing polyoxotungstates have anti-influenza-virus activity. In this paper, the binding mechanisms of five isomers of di-Ti-substituted polyoxotungstate, [α-1,2-PTi₂W₁₀O₄₀]^7- (α-1,2), [α-1,6-PTi₂W₁₀O₄₀]^7- (α-1,6), [α-1,5-PTi₂W₁₀O₄₀]^7- (α-1,5), [α-1,4-PTi₂W₁₀O₄₀]^7- (α-1,4) and [α-1,11-PTi₂W₁₀O₄₀]^7- (α-1,11), to five subtypes of influenza virus A neuraminidase (FluV-A NA) were investigated in the context of aqueous solution by using molecular docking and molecular dynamics studies. The results show that the isomer α-1,2 is superior to other isomers as a potential inhibitor to neuraminidase. The positively charged arginine residues around the active site of NA could be induced by negatively charged POM to adapt themselves and could form salt bridge interactions and hydrogen bond interactions with POM. The binding free energies of POM/NA complexes range from -5.36 to -8.31 kcal mol^-1. The electrostatic interactions are found to be the driving force during the binding process of POM to NA. The conformational analysis shows that POM tends to bind primarily with N1 and N8 at the edge of the active pocket, which causes the conformational change of the pincers structure comprising residue 347 and loop 150. Whereas, the active pockets of N2, N9 and N4 are found to be more spacious, which allows POM to enter into the active pockets directly and anchor there firmly. This study shows that negatively charged ligand as POM could induce the reorganization of the active site of NA and highlights POM as a promising inhibitor to NA despite the ever increasing mutants of NA.

Electronic Supplementary Material

Supplementary material is available for this article at 10.1007/s11434-010-3271-8 and is accessible for authorized users.

Current and Novel Inhibitors of HIV Protease

The design, development and clinical success of HIV protease inhibitors represent one of the most remarkable achievements of molecular medicine. This review describes all nine currently available FDA-approved protease inhibitors, discusses their pharmacokinetic properties, off-target activities, side-effects, and resistance profiles. The compounds in the various stages of clinical development are also introduced, as well as alternative approaches, aiming at other functional domains of HIV PR. The potential of these novel compounds to open new way to the rational drug design of human viruses is critically assessed.

A multitechnique study of europium decatungstate and human serum albumin molecular interaction

Polyoxometalates (POMs) show promising biological activities, but the mechanism of these potential therapeutic effects remains to be elucidated at a molecular level. As a step in this direction, the interaction between the Eu-containing decatungstate [EuW(10)O(36)](9-) and human serum albumin (HSA) has been studied by several techniques. Fluorescence/luminescence analysis showed the existence of a strong interaction between the POM and HSA. This interaction has key effects both on luminescence of the POM and on the behaviours of HSA. An enhancement of the POM luminescence is observed upon interaction. The presence of increasing concentrations of the POM results in the progressive quenching of the fluorescence of the single tryptophan of HSA. Circular dichroism led to the conclusion that the binding of the POM did not alter the secondary structure of HSA. Isothermal titration calorimetry revealed an enthalpy-driven binding reaction between HSA and the POM, resulting in the formation of a 1:1 complex. The present work is meaningful in finding novel solid state bio-image or fluorescence/luminescence labelling agents.

Preparation and characterization of polyoxometalate-modified poly(vinyl alcohol)/polyethyleneimine hybrids as a chemical and biological self-detoxifying material

Nanohybrid membranes based on the Keggin-type polyoxometalate (POM) H5PV2Mo10O40 and a poly(vinyl alcohol)/polyethyleneimine (PVA/PEI) blend were prepared as a chemical and biological protective material. The objective of the study was to develop and evaluate permeable membranes (PVA/PEI) impregnated with reactive nanoparticulates (POM) that can protect against simulants of chemical and biological warfare agents. The physical properties of the PVA/PEI-POM hybrids were examined using SEM, TEM, TGA, and UV-Vis spectroscopy, the results of which indicated that the POM was incorporated in the PVA/PEI matrix after impregnation. The redox properties against 2-chloroethyl-ethyl sulfide (CEES) were investigated based on significant color changes and UV absorption in the POM upon reduction by CEES. The antibacterial effects of the PVA/PEI-POM hybrids were assessed by the zone of inhibition, minimum inhibitory concentration (MIC), and plate-counting methods. The results of this study showed that PVA/PEI-POM hybrids that act against simulants of chemical and biological weapons while retaining their ability to transmit moisture vapor could be obtained.

Polyoxometalates as effective inhibitors for sialyl- and sulfotransferases

Sialylated and/or sulfated carbohydrate chains in glycoproteins and glycolipids play important roles in infection by microorganisms and diseases including cancer. Inhibitors of sialyl/sulfotransferases, responsible for the biosynthesis of these carbohydrate chains, could be medical agents against such infections and diseases. Polyoxometalates (PMs) are inorganic polyanionic molecules that have been shown to exhibit activity against tumors and infectious microorganisms; however, the effects of PMs on carbohydrate biosynthesis have never been investigated. Here, we found that some types of PMs can inhibit the enzymatic activities of specific sialyl/sulfotransferases. Several tungstate-type PMs inhibited Gal: alpha2,3-sialyltransferase-I (ST3Gal-I) activity at sub-nanomolar levels. The half-inhibitory concentration of the best inhibitors was 0.2 nM and the inhibition was non-competitive for both donor and acceptor substrates (Ki values approximately 0.5 nM). By certain vanadate-type PMs, ST3Gal-I and Gal 3-O-sulfotransferase-2 (Gal3ST-2) were specifically inhibited at nanomolar levels. The inhibitory effect of a tungstate-type PM on ST3Gal-I was reversible and electrostatic. A ST3Gal-I mutant protein which was converted (335)Arg residue in the C-terminal region to Glu, was rather insensitive to the PM, suggesting that specific C-terminal basic amino acid of ST3Gal-I is involved in the binding to PMs. Collectively, PMs are novel inhibitors of specific sialyl/sulfotransferases.

Preparation and antibacterial efficacy of bamboo charcoal/polyoxometalate biological protective material

Nanocomposites based on Keggin-type polyoxometalate H₅PV₂Mo₁₀O₄₀ (POM) and porous bamboo charcoal (BC) were prepared by activation and immobilization processes. The physical properties of the BC/POM composites were examined using FTIR, UV-Vis spectroscope, ³¹P MAS-NMR, SEM and TEM. These techniques indicated that the POM was intact on the surface of the BC matrix after impregnation. The POM particle size was found to be less than 150 nm based on TEM. The antibacterial effects of the BC/POM composites were assessed from the zone of inhibition, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and plate-counting method, and an excellent antibacterial performance was discovered.

Identification of polyoxometalates as nanomolar noncompetitive inhibitors of protein kinase CK2

Protein kinase CK2 is a multifunctional kinase of medical importance that is dysregulated in many cancers. In this study, polyoxometalates were identified as original CK2 inhibitors. [P2Mo18O62](6-) has the most potent activity. It inhibits the kinase in the nanomolar range by targeting key structural elements located outside the ATP- and peptide substrate-binding sites. Several polyoxometalate derivatives exhibit strong inhibitory efficiency, with IC50 values < or = 10 nM. Furthermore, these inorganic compounds show a striking specificity for CK2 when tested in a panel of 29 kinases. Therefore, polyoxometalates are effective CK2 inhibitors in terms of both efficiency and selectivity and represent nonclassical kinase inhibitors that interact with CK2 in a unique way. This binding mode may provide an exploitable mechanism for developing potent drugs with desirable properties, such as enhanced selectivity relative to ATP-mimetic inhibitors.

Solution kinetics measurements suggest HIV-1 protease has two binding sites for darunavir and amprenavir

Darunavir, a potent antiviral drug, showed an unusual second binding site on the HIV-1 protease dimer surface of the V32I drug resistant mutant and normal binding in the active site cavity. Kinetic analysis for wild type and mutant protease showed mixed-type competitive-uncompetitive inhibition for darunavir and the chemically related amprenavir, while saquinavir showed competitive inhibition. The inhibition model is consistent with the observed second binding site for darunavir and helps to explain its antiviral potency.

Structural characterization and reactivity of gamma-octamolybdate functionalized by proline

The reaction of molybdate and dl-proline at pH 3.4 results in the formation of a Na(4)[Mo(8)O(26)(proO)(2)] x 22H(2)O complex (pro=proline) in which two proline ligands are attached to molybdenum(VI) ions via monodentate coordination of the carboxylate groups. The structure of the complex was determined by single crystal X-ray diffraction and by combination of (1)H, (13)C and (95)Mo NMR spectroscopy techniques in solution. The structure of the complex is strongly dependent on the pH. At native pH 3.4 the octamolybdate-type structure seems to be present in solution, but the increase of pH to 5.8 resulted in a rearrangement of the structure to a heptamolybdate-type structure. At physiological pH, the polyoxometalate framework was completely dissociated into the monomeric MoO(4)(2-) unit. The reactivity of the Na(4)[Mo(8)O(26)(proO)(2)] x 22H(2)O towards the hydrolysis of ATP was tested at different pH values. While in solution at pH 3.4 the hydrolysis proceeded to yield AMP (adenosine monophosphate) and ADP (adenosine diphosphate) in nearly equal amounts, reaction mixture at pH 5.8 gave ADP as the only product of hydrolysis after 24h of reaction. At neutral pH, the hydrolysis of ATP was slower, but it proceeded to yield 75% of ADP after 48 h of reaction.