Establishment of the method for screening the potential targets and effective components of huatuo reconstruction pill.

Huatuo reconstruction pill (HTRP) is a traditional Chinese medicine prescription that mainly treats for hemiplegia and postoperation of brain stroke. Existing pharmacological studies have previously shown that HTRP could inhibit in vitro thrombosis, delay platelet adhesion, dilate blood vessels, and improve the microcirculation disturbances. In this paper, we chiefly concerned about the potential targets of HTRP and tried to figure out the active components of it. Computer-aided drug design method was emploied to search for the active components and explain the mechanism between the targets and the small molecules at molecular lever. The potential targets of this compound pharmaceutics were searched through relevant pharmacological studies and three pharmacophore models which involved the platelet activating factor (PAF) receptor, the angiotensin converting enzyme (ACE) and the 5-hydroxytryptamine receptor (5-HT2A) were constructed by Discotech method of Sybyl. Thus, the candidate compounds which agreed with the pharmacophore models were obtained by the virtual screening to the known ingredients of HTRP. Based on that, sequence and structure prediction of the unknown targets were realized by homology modeling which were used for molecular docking with those candidate compounds. Results showed that three compounds, which may prove to be valid to these targets, got higher scores than the existing corresponding inhibitors after molecular docking, including ferulic acid, onjixanthone I and albiflorin. And the three molecules may refer to the singificant substances to the total compounds of HTRP which were effective to the disease.

Impact of resistance mutations on inhibitor binding to HIV-1 integrase.

HIV-1 integrase (IN) is essential for HIV-1 replication, catalyzing two key reaction steps termed 3' processing and strand transfer. Therefore, IN has become an important target for antiviral drug discovery. However, mutants have emerged, such as E92Q/N155H and G140S/Q148H, which confer resistance to raltegravir (RAL), the first IN strand transfer inhibitor (INSTI) approved by the FDA, and to the recently approved elvitegravir (EVG). To gain insights into the molecular mechanisms of ligand binding and drug resistance, we performed molecular dynamics (MD) simulations of homology models of the HIV-1 IN and four relevant mutants complexed with viral DNA and RAL. The results show that the structure and dynamics of the 140s' loop, comprising residues 140 to 149, are strongly influenced by the IN mutations. In the simulation of the G140S/Q148H double mutant, we observe spontaneous dissociation of RAL from the active site, followed by an intrahelical swing-back of the 3'-OH group of nucleotide A17, consistent with the experimental observation that the G140S/Q148H mutant exhibits the highest resistance to RAL compared to other IN mutants. An important hydrogen bond between residues 145 and 148 is present in the wild-type IN but not in the G140S/Q148H mutant, accounting for the structural and dynamical differences of the 140s' loop and ultimately impairing RAL binding in the double mutant. End-point free energy calculations that broadly capture the experimentally known RAL binding profiles elucidate the contributions of the 140s' loop to RAL binding free energies and suggest possible approaches to overcoming drug resistance.

Enhanced stability of thylakoid membrane proteins and antioxidant competence contribute to drought stress resistance in the tasg1 wheat stay-green mutant.

A wheat stay-green mutant, tasg1, was previously generated via mutation breeding of HS2, a common wheat cultivar (Triticum aestivum L.). Compared with wild-type (WT) plants, tasg1 exhibited delayed senescence indicated by the slower degradation of chlorophyll. In this study, the stability of proteins in thylakoid membranes was evaluated in tasg1 under drought stress compared with WT plants in the field as well as in seedlings in the laboratory. Drought stress was imposed by controlling irrigation and sheltering the plants from rain in the field, and by polyethylene glycol (PEG)-6000 in the laboratory. The results indicated that tasg1 plants could maintain higher Hill activity, actual efficiency (ΦPSII), maximal photochemical efficiency of PSII (Fv/Fm), and Ca(2+)-ATPase and Mg(2+)-ATPase activities than the WT plants under drought stress. Furthermore, the abundance of some polypeptides in thylakoid membranes of tasg1 was greater than that in the WT under drought stress. Expression levels of TaLhcb4 and TaLhcb6 were higher in tasg1 compared with the WT. Under drought stress, the accumulation of superoxide radical (O2·(-)) and hydrogen peroxide (H2O2) was lower in tasg1 compared with the WT not only at the senescence stage but also at the seedling stages. These results suggest greater functional stability of thylakoid membrane proteins in tasg1 compared with the WT, and the higher antioxidant competence of tasg1 may play an important role in the enhanced drought tolerance of tasg1.

Virtual screening for natural product inhibitors of HIV-1 integrase.

Since there is no human homolog of this enzyme, HIV-1 integrase (IN) represents a rational and important target for treating HIV infection and preventing AIDS. The 3D structure of full-length HIV-1 IN, either separately or in complex with its inhibitors, has been lacking. Thus, scarce information about the interactions between the HIV-1 IN and its inhibitors can be referenced. To more rationally design potent HIV-1 IN inhibitors, we have previously constructed a model of the full-length HIV-1 IN tetramer and a model of the protein-viral DNA complex, as well as the pharmacophore model of HIV-1 IN strand transfer inhibitors (INSTIs). In this paper, the pharmacophore model of INSTIs was used as a 3D query to screen the Traditional Chinese Medicine Database (TCMD). The hit compounds were further filtered by Lipinski's Rule of Five and docking study to refine the retrieved hits. Finally, 9 suitable ligands with similar structures belonging to the thioglycosides were selected. Subsequent molecular dynamics simulation showed that these compounds had interactions with HIV-1 IN binding site and their possible function as IN inhibitors was discussed.

Agaritine and its derivatives are potential inhibitors against HIV proteases.

Agaritine, or beta-N-[gamma-L(+)-glutamyl]-4-hydroxymethylphenylhydrazine, is a Chinese herbal medicine, known having the antiviral and anticancer function. However, so far no reports whatsoever have been made for its potential as an anti-HIV agent. It was observed by docking experiments for more than 9,000 compounds extracted from various Chinese medicines that the compound agaritine distinguished itself from all the others in binding to the HIV protease with the most favorable free energy. Based on this, a series of derivatives were generated by modifying agaritine. It has been observed thru an extensive docking study that some of agaritine derivatives had markedly stronger binding interaction with the HIV protease than agaritine, suggesting that these derivatives might be good candidates for developing drugs for AIDS therapy.

Molecular insights of SAH enzyme catalysis and implication for inhibitor design.

Biological transmethylation reaction is a key step in the duplication of virus life cycle, in which S-adenosylmethionine plays as the methyl donor. The product of this reactions, S-adenosylhomocysteine (AdoHcy) inhibits the transmethylation process. AdoHcy is hydrolysed to adenosine and L-homocysteine by the action of S-adenosylhomocysteine hydrolase (SAH). Thus the virus life cycle should be cut off once the action of SAH is inhibited. Our study was focussed on the discovery of potential inhibitor against SAH. We performed a similarity search in Traditional Chinese Medicine Database and retrieved 17 hits with high similarity. After that we virtually docked the 17 compounds as well as the natural substrates to the hydrolase using Autodock 3.0.1 software. Then we discussed about the mechanism of the inhibition reaction, followed by proposing the potential inhibitors by comparing best docked solutions and possible modification for the best inhibitors.

[Screening of new HIV inhibitors based on the database of traditional Chinese medicine].

AIM: To report the preliminary result of the HIV inhibitor screening based on cheminformatics tools and the traditional Chinese medicine database. METHODS: Database search was carried out with saquinavir molecule as a template, further screening was made with docking. Detailed studies using molecular dynamics simulation of 50 ps and 200 ps were made with respect to a potential leading compound, leucovorin. RESULTS: The leucovorin molecule distinguished from other molecules as a potential drug candidate and is subject to extensive studies. The bonding profile and energy were calculated with MD simulations. CONCLUSION: Our results could be very helpful when we modify leucovorin or design new inhibitors against HIV.