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Polyketide metabolism‐associated proteins in Mycobacterium tuberculosis play an essential role in the survival of the bacterium, which makes them potential drug targets for the treatment of tuberculosis (TB). The novel ribonuclease protein Rv1546 is predicted to be a member of the steroidogenic acute regulatory protein‐related lipid‐transfer (START) domain superfamily, which comprises bacterial polyketide aromatase/cyclases (ARO/CYCs). Here, we determined the crystal structure of Rv1546 in a V‐shaped dimer. The Rv1546 monomer consists of four α‐helices and seven antiparallel β‐strands. Interestingly, in the dimeric state, Rv1546 forms a helix‐grip fold, which is present in START domain proteins, via three‐dimensional domain swapping. Structural analysis revealed that the conformational change of the C‐terminal α‐helix of Rv1546 might contribute to the unique dimer structure. Site‐directed mutagenesis followed by in vitro ribonuclease activity assays was performed to identify catalytic sites of the protein. This experiment suggested that surface residues R63, K84, K88, and R113 are important in the ribonuclease function of Rv1546. In summary, this study presents the structural and functional characterization of Rv1546 and supplies new perspectives for exploiting Rv1546 as a novel drug target for TB treatment. PDB Code(s): 8H0H and 8H2D; [ABSTRACT FROM AUTHOR]

Rationale: The production of bottled water requires a forensic discriminant technique that enables the identification of the brands or accidents caused by intended contaminants. The bottled water poisoning crimes have drawn much attention, and such crimes may recur in the future. The water is colorless and odorless, and thus it is difficult to detect contaminated water through visual observation. Thus, bottled water can be easily exploited for poisoning, and a method for tracing their origin is currently required. Methods: In this study, a total of 27 brands of bottled water samples were analyzed to determine stable oxygen isotopes, strontium isotopes, major and trace elements. The geographical origin of the water was traced based on the climatic and geographical characteristics of the location from where water was sourced, which was assumed to be reflected in the bottled water. Furthermore, we investigated whether this method can be applied to identify bottled water products. Results: The results demonstrated that the characteristics of the bottled water, including the oxygen stable isotope ratios, reflect the latitude and altitude of bottled water source in South Korea, from the high‐latitude region to the coastal regions. In addition, the results indicated that excellent discrimination was achieved using strontium isotopes to identify source areas with different types of bedrock, complex underlying lithologies, and ocean areas in South Korea. A statistical method based on discriminant analysis was applied to measure trace elements, and the results effectively reflected the characteristics of water–rock interactions (cross‐validated classification probability: ≥92%). Conclusions: These data suggest that the geographical characteristics of the source area are well reflected in commercial bottled water in South Korea. The proposed analytical methods can be utilized to trace the geographical origin of different bottled water samples and identify bottled water products used in poisoning crimes. [ABSTRACT FROM AUTHOR]

Toxin–antitoxin (TA) systems regulate key cellular functions in bacteria. Here, we report a unique structure of the Streptococcus pneumoniae HigBA system and a novel antimicrobial agent that activates HigB toxin, which results in mRNA degradation as an antibacterial strategy. In this study, protein structure‐based peptides were designed and successfully penetrated the S. pneumoniae cell membrane and exerted bactericidal activity. This result represents the time during which inhibitors triggered S. pneumoniae cell death via the TA system. This discovery is a remarkable milestone in the treatment of antibiotic‐resistant S. pneumoniae, and the mechanism of bactericidal activity is completely different from those of current antibiotics. Furthermore, we found that the HigBA complex shows a crossed‐scissor interface with two intermolecular β‐sheets at both the N and C termini of the HigA antitoxin. Our biochemical and structural studies provided valuable information regarding the transcriptional regulation mechanisms associated with the structural variability of HigAs. Our in vivo study also revealed the potential catalytic residues of HigB and their functional relationships. An inhibition study with peptides additionally proved that peptide binding may allosterically inhibit HigB activity. Overall, our results provide insights into the molecular basis of HigBA TA systems in S. pneumoniae, which can be applied for the development of new antibacterial strategies. Databases: Structural data are available in the PDB database under the accession number 6AF4. [ABSTRACT FROM AUTHOR]

Transcriptional regulator proteins are closely involved in essential survival strategies in bacteria. AcrR is a one‐component allosteric repressor of the genes associated with lipid transport and antibiotic resistance. When fatty acid ligands bind to the C‐terminal ligand‐binding cavity of AcrR, a conformational change in the N‐terminal operator‐binding region of AcrR is triggered, which releases the repressed DNA and initiates transcription. This paper focuses on the structural transition mechanism of AcrR of Mycobacterium tuberculosis upon DNA and ligand binding. AcrR loses its structural integrity upon ligand‐mediated structural alteration and bends toward the promoter DNA in a more compact form, initiating a rotational motion. Our functional characterization of AcrR and description of the ligand‐ and DNA‐recognition mechanism may facilitate the discovery of new therapies for tuberculosis. [ABSTRACT FROM AUTHOR]

The tumor suppressor phosphatase and tensin homologue (PTEN) has phosphatase activity, with phosphatidylinositol (3,4,5)-trisphosphate (PIP3), a product of phosphatidylinositol 3-kinase (PI3K), as one of the principal substrates. PTEN is a negative regulator of the Akt pathway, which plays a fundamental role in controlling cell growth, survival, and proliferation. Loss of PTEN function has been observed in many different types of cancer. Functional inactivation of PTEN as a consequence of germ-line mutations or promoter hypermethylation predisposes individuals to malignancies. PTEN undergoes posttranslational modifications, such as oxidation, acetylation, phosphorylation, SUMOylation, and ubiquitination, which influence its catalytic activity, interactions with other proteins, and subcellular localization. Cellular redox status is crucial for posttranslational modification of PTEN and its functional consequences. Oxidative stress and inflammation are major causes of loss of PTEN function. Pharmacologic or nutritional restoration of PTEN function is considered a reliable strategy in the management of PTEN-defective cancer. In this review, we highlight natural compounds, such as curcumin, indol-3 carbinol, and omega-3 fatty acids, that have the potential to restore or potentiate PTEN expression/activity, thereby suppressing cancer cell proliferation, survival, and resistance to chemotherapeutic agents. [ABSTRACT FROM AUTHOR]

Background Recent studies have shown that Helicobacter pylori ( H. pylori) activates signal transducer and activator of transcription 3 (STAT3) that plays an important role in gastric carcinogenesis. However, the molecular mechanism underlying H. pylori-mediated STAT3 activation is still not fully understood. In this study, we investigated H. pylori-induced activation of STAT3 signaling in AGS human gastric cancer cells and the underlying mechanism. Materials and Methods AGS cells were cocultured with H. pylori, and STAT3 activation was assessed by Western blot analysis, electrophoretic mobility shift assay and immunocytochemistry. To demonstrate the involvement of reactive oxygen species (ROS) in H. pylori-activated STAT3 signaling, the antioxidant N-acetylcysteine was utilized. The expression and production of interleukin-6 (IL-6) were measured by reverse-transcription polymerase chain reaction and enzyme-linked immunosorbent assay (ELISA), respectively. The interaction between IL-6 and IL-6 receptor (IL-6R) was determined by the immunoprecipitation assay. Results H. pylori activates STAT3 as evidenced by increases in phosphorylation on Tyr705, nuclear localization, DNA binding and transcriptional activity of this transcription factor. The nuclear translocation of STAT3 was also observed in H. pylori-inoculated mouse stomach. In the subsequent study, we found that H. pylori-induced STAT3 phosphorylation was dependent on IL-6. Notably, the increased IL-6 expression and the IL-6 and IL-6R binding were mediated by ROS produced as a consequence of H. pylori infection. Conclusions H. pylori-induced STAT3 activation is mediated, at least in part, through ROS-induced upregulation of IL-6 expression. These findings provide a novel molecular mechanism responsible for H. pylori-induced gastritis and gastric carcinogenesis. [ABSTRACT FROM AUTHOR]

To improve the antimicrobial activity of the hydrocarbon-stapled amphipathic heptapeptide helix identified from our previous study, we prepared a series of its dimeric analogs using several different linkers. All of these dimers showed a significant increase in antimicrobial activity although their hemolytic activity was also largely increased. One particular analog bearing a proline linker displayed notably low hemolytic activity compared to others, indicating that the conformational characteristics of the linker play a key role in disassociating undesirable hemolytic activity from antimicrobial activity in this series of antimicrobial peptides. We believe that this analog can serve as a stepping stone for further development of novel antimicrobial agents to combat antibiotic-resistance. [ABSTRACT FROM AUTHOR]

In our previous study, we showcased the potential of an all-hydrocarbon stapled heptapeptide as a privileged scaffold for the design of artificial antimicrobial peptides. We demonstrated that the amphipathic helicity and the subtle balance between hydrophobicity and hydrophilicity are important structural features for the antimicrobial activities of this class of antimicrobial agents. In this study, we show that elimination of the N-acetyl cap can further improve the pharmacological properties of the most potent stapled heptapeptides. The structure-activity relationships newly established in this study would serve as a critical asset for the further development of a new class of antimicrobial agents to combat the rising problem of antibiotic resistance. [ABSTRACT FROM AUTHOR]

HU, one of the major nucleoid-associated proteins, interacts with the minor groove of DNA in a nonspecific manner to induce DNA bending or to stabilize bent DNA. In this study, crystal structures are reported for both free HU from Staphylococcus aureus Mu50 (SHU) and SHU bound to 21-mer dsDNA. The structures, in combination with electrophoretic mobility shift assays (EMSAs), isothermal titration calorimetry (ITC) measurements and molecular-dynamics (MD) simulations, elucidate the overall and residue-specific changes in SHU upon recognizing and binding to DNA. Firstly, structural comparison showed the flexible nature of the β-sheets of the DNA-binding domain and that the β-arms bend inwards upon complex formation, whereas the other portions are nearly unaltered. Secondly, it was found that the disruption and formation of salt bridges accompanies DNA binding. Thirdly, residue-specific free-energy analyses using the MM-PBSA method with MD simulation data suggested that the successive basic residues in the β-arms play a central role in recognizing and binding to DNA, which was confirmed by the EMSA and ITC analyses. Moreover, residue Arg55 resides in the hinge region of the flexible β-arms, exhibiting a remarkable role in their flexible nature. Fourthly, EMSAs with various DNAs revealed that SHU prefers deformable DNA. Taken together, these data suggest residue-specific roles in local shape and base readouts, which are primarily mediated by the flexible β-arms consisting of residues 50-80. [ABSTRACT FROM AUTHOR]

Activated microglia produces diverse neurotoxic factors such as nitric oxide (NO) and tumor necrosis factor-α that serve as apoptotic inducers resulting in various neurodegenerative diseases. The inhibition of microglia-derived NO production by inducible nitric oxide synthase (iNOS) has been reported to be beneficial in retarding neurodegenerative disorders. Three active lignans have been isolated from the flower buds of Magnolia fargesii by the bioassay-guided fractionation using lipopolysaccharide (LPS)-activated BV-2 microglial cell culture system. The structures of them were identified as kobusin (1), aschantin (2) and fargesin (3) by the analyses of spectroscopic data. They inhibited the production of NO by activated microglia. Their IC50 values were 21.8 ± 3.7, 14.8 ± 2.5 and 10.4 ± 2.8 μg/mL, respectively. They suppressed LPS-induced NF-κB activation and the expression of iNOS protein and mRNA. Furthermore, they showed scavenging activity of neurotoxic peroxynitrite that can be produced by NO and superoxide anion. These results imply that lignans from Magnolia fargesii might be beneficial for the treatment of neuro-inflammatory diseases through the inhibition of iNOS expression and peroxynitrite scavenging potential. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Extracts of Artemisia plants possess anti-inflammatory and antioxidative activities. Eupatilin (5,7-dihydroxy-3′,4′,6-tri-methoxy-flavone), a pharmacologically active flavone derived from Artemisia asiatica, was shown to inhibit phorbol ester-induced cyclooxygenase-2 expression and NF-κB activation in mouse skin, and also to induce cell cycle arrest in ras-transformed human mammary epithelial (MCF10A- ras) cells. In this article, we examined the ability of jaceosidin (4′,5,7-trihydroxy-3′,6-dimethoxyflavone) isolated from Artemisia argyi to inhibit the proliferation of MCF10A- ras cells. Jaceosidin reduced the viability of MCF10A- ras cells to a greater extent than eupatilin. Jaceosidin treatment resulted in increased intracellular accumulation of reactive oxygen species (ROS) in MCF10A- ras cells, which was blocked by the antioxidant N-acetylcysteine (NAC). NAC attenuated jaceosidin-induced cytotoxicity. To better assess the proapoptotic effects of jaceosidin, we analyzed the treated cells by the flow cytometry. MCF10A- ras cells treated with jaceosidin (100 μM) exhibited the increased proportion of hypodiploid or apoptotic cells (48.72% as composed to 7.78% in control cells). Jaceosidin treatment also increased the ratio of proapoptotic Bax to the antiapoptotic Bcl-2 and induced the cleavage of caspase-3 and poly(ADP-ribose)polymerase (PARP). Moreover, jaceosidin elevated the expression of p53 and p21, while the compound inhibited the activation of ERK1/2 that is an important component of cell survival signaling. [ABSTRACT FROM AUTHOR]

The article presents a case study of a 37-year-old man who was presented the emergency department with an incident of near-drowning. The patient has underwent laboratory and physical examinations and was noted with mild pre-tibial pitting oedema, haemoglobin and creatine phosphokinase. His hypoxic injury revealed acute kidney injury and Ischaemic acute tubular necrosis.