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1.
Eur J Med Chem ; 187: 111941, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31821989

RESUMO

Threonyl-tRNA synthetase (ThrRS) is a key member of the aminoacyl-tRNA synthetase (aaRS) family that plays essential roles in protein biosynthesis, and ThrRS inhibitors have potential in the therapy of multiple diseases, such as microbial infections and cancers. Based on a unique tRNA-amino acid dual-site inhibitory mechanism identified recently with the herb-derived prolyl-tRNA synthetase (ProRS) inhibitor halofuginone (HF), a series of compounds have been designed and synthesized by employing a fragment-based target hopping approach to simultaneously target the tRNAThr and l-threonine binding pockets of ThrRS. Among them, compound 30d showed an IC50 value of 1.4 µM against Salmonella enterica ThrRS (SeThrRS) and MIC values of 16-32 µg/mL against the tested bacterial strains. The cocrystal structure of SeThrRS in complex with 30d was determined at high resolution, revealing that 30d simultaneously occupies both binding pockets for the nucleotide A76 of tRNAThr and l-threonine in an ATP-independent manner, a novel mechanism compared to all other reported ThrRS inhibitors. Our study provides a new class of ThrRS inhibitors, and more importantly, it presents the first experimental evidence that the tRNA-amino acid dual-site inhibitory mechanism could apply to other aaRSs beyond ProRS, thus providing great opportunities for designing new mechanistic inhibitors for aaRS-based therapeutics.

2.
Biochem Biophys Res Commun ; 508(3): 882-888, 2019 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-30538042

RESUMO

Gambogenic acid (GNA), an active ingredient isolated from Gamboge, which possesses diverse antitumor effects in vivo and vitro. Here we were mainly designed to understand the role of GNA in drug resistance in HepG2/Adr cells. The alteration of cytotoxic drugs IC50 was examined using the MTT method. Cell apoptosis and uptake of P-glycoprotein (P-gp) substrates were measured under a flow cytometry and fluorescence microscope, respectively. Moreover, the ATPase activity, the expression of P-gp and P-gp-related proteins were also investigated. Results of the MTT method indicated that GNA increased the chemosensitivity of doxorubicin (DOX) and paclitaxel (PTX) in the HepG2/Adr cells and promoted the cell apoptosis in the presence of DOX. Meanwhile, it was also increased the retention of P-gp substrates DOX and Rhodamine 123 (Rho-123) while did not affect the ATPase activity. Furthermore, the down-regulation of P-gp expression could be contributed to multidrug resistance (MDR) upon a reversal concentration of 0.8 µg/mL GNA. Mechanistically, the expression of P-gp was reduced by GNA may result from the inhibition of the NF-kB and MAPK pathway. Collectively, GNA could be a potential inhibitor to reverse P-gp-mediated MDR in liver cancer therapy.


Assuntos
Membro 1 da Subfamília B de Cassetes de Ligação de ATP/metabolismo , Protocolos de Quimioterapia Combinada Antineoplásica/farmacologia , Neoplasias Hepáticas/metabolismo , Xantenos/farmacologia , Membro 1 da Subfamília B de Cassetes de Ligação de ATP/genética , Adenosina Trifosfatases/metabolismo , Apoptose , Doxorrubicina/metabolismo , Resistência a Múltiplos Medicamentos , Resistencia a Medicamentos Antineoplásicos , Células Hep G2 , Humanos , Neoplasias Hepáticas/enzimologia , Neoplasias Hepáticas/genética , Proteínas Quinases Ativadas por Mitógeno/metabolismo , NF-kappa B/metabolismo , Rodamina 123/análise
3.
Medchemcomm ; 9(10): 1619-1629, 2018 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-30429968

RESUMO

Discovery of new drug binding sites on well-established targets is of great interest as it facilitates the design of new mechanistic inhibitors to overcome the acquired drug resistance. Small chemical fragments can easily enter and bind to the cavities on the protein surface. Thus, they can be used to probe new druggable pockets in proteins. DNA gyrase plays indispensable roles in DNA replication, and both its GyrA and GyrB subunits are clinically validated antibacterial targets. New mechanistic GyrB inhibitors are urgently desired since the withdrawal of novobiocin from the market by the FDA due to its reduced efficiency and other reasons. Here, a fragment library was screened against the E. coli GyrB ATPase domain by combining affinity- and bioactivity-based approaches. The following X-ray crystallographic efforts were made to determine the cocrystal structures of GyrB with ten fragment hits, and three different binding modes were disclosed. Fortunately, a hydrophobic pocket which is previously unknown was identified by two fragments. Fragments that bind to this pocket were shown to inhibit the ATPase activity as well as the DNA topological transition activity of DNA gyrase in vitro. A set of fragment analogs were screened to explore the binding capacity of this pocket and identify the better starting fragments for lead development. Phylogenetic analysis revealed that this pocket is conserved in most Gram-negative and also many Gram-positive human pathogenic bacteria, implying a broad-spectrum antibacterial potential and a lower risk of mutation. Thus, the novel druggable pocket and the starting fragments provide a novel basis for designing new GyrB-targeting therapeutics.

4.
J Phys Chem B ; 109(18): 8774-8, 2005 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-16852041

RESUMO

Size-controllable tin oxide nanoparticles are prepared by heating ethylene glycol solutions containing SnCl(2) at atmospheric pressure. The particles were characterized by means of transmission electron microscopic (TEM), X-ray diffraction (XRD) studies. TEM micrographs show that the obtained material are spherical nanoparticles, the size and size distribution of which depends on the initial experimental conditions of pH value, reaction time, water concentration, and tin precursor concentration. The XRD pattern result shows that the obtained powder is SnO(2) with tetragonal crystalline structure. On the basis of UV/vis and FTIR characterization, the formation mechanism of SnO(2) nanoparticles is deduced. Moreover, the SnO(2) nanoparticles were employed to synthesize carbon-supported PtSnO(2) catalyst, and it exhibits surprisingly high promoting catalytic activity for ethanol electrooxidation.

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