• Journal of the Korean Magnetic Resonance Society
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• v.9 no.2
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• pp.110-121
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• 2005

E.coli methionyl tRNA synthetase consist of 676 amino acids and plays a key role in initiation of protein synthesis. The native form of this enzyme is a homodimer, but the monomeric enzyme truncated approximately C-terminal 120 amino acids retains the full enzymatic activities. X-ray crystal structure of the active monomeric enzyme shows that it has two domains. The N-terminal domain is thought to be a binding site for acceptor stem of tRNA, ATP, and methionine. The C-terminal domain is mainly a-helical and makes an interaction with the anticodon of $tRNA^{Met}$. Especially it is suggested that the region of helix-loop-helix including the tryptophan residue at the position 461 may be the essential for the interaction with anticodon of $tRNA^{Met}$. In this work the structure and function of E. coli methionyl-tRNA synthetase was studied by spectroscopic method (NMR, CD, Fluorescence). The importance of tryptophan residue at the position 461 was investigated by fluorescence spectroscopy. Tryptophan 461 is expected to be an essential site for the interaction between E. coli methionyl-tRNA synthetase and E. coli $tRNA^{Met}$. Proton and heteonuclear 2-dimensional NMR spectroscopy were also used to elucidate the protein-tRNA interaction.

• Journal of Life Science
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• v.14 no.5
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• pp.752-760
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• 2004

The function of the [4Fe-4S] cluster containing iron (Fe-) protein in nitrogenase catalysis is to serve as the nucleotide-dependent electron donor to the MoFe protein which contains the sites for substrate binding and reduction. The ability of the Fe protein to function in this manner is dependent on its ability to adopt the appropriate conformation for productive interaction with the MoFe protein and on its ability to change redox potentials to provide the driving force required for electron transfer. The MgADP-bound (or off) conformational state of the nitrogenase Fe protein structure described reveals mechanisms for long-range communication from the nucleotide-binding sites to control affinity of association with the MoFe protein component. Two pathways, termed switches I and II, appear to be integral to this nucleotide signal transduction mechanism. In addition, the structure of the MgADP bound Fe protein provides the basis for the changes in the biophysical properties of the [4Fe-4S] observed when Fe protein binds nucleotides. The structures of the nitrogenase Fe protein with defined amino acid substitutions in the nucleotide dependent signal transduction pathways of the Switch I and Switch II have been determined by X-ray diffraction methods. These two pathways have been also implicated by site directed mutagenesis studies, structural analysis and analogies to other proteins that utilize similar nucleotide dependent signal transduction pathways. We have examined the validity of the assignment of these pathways in linking the signals generated by MgATP binding and hydrolysis to macromolecular complex formation and intermolecular electron transfer. The results provide a structural basis for the observed biophysical and biochemical properties of the Fe protein variants and interactions within the nitrogenase Fe protein-MoFe protein complex.

• BMB Reports
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• v.53 no.3
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• pp.142-147
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• 2020

Lipid accumulation in white adipose tissue is the key contributor to the obesity and orchestrates numerous metabolic health problems such as type 2 diabetes, hypertension, atherosclerosis, and cancer. Nonetheless, the prevention and treatment of obesity are still inadequate. Recently, scientists found that brown adipose tissue (BAT) in adult humans has functions that are diametrically opposite to those of white adipose tissue and that BAT holds promise for a new strategy to counteract obesity. In this study, we evaluated the potential of sinapic acid (SA) to promote the thermogenic program and lipolysis in BAT. SA treatment of brown adipocytes induced the expression of brown-adipocyte activation-related genes such as Ucp1, Pgc-1α, and Prdm16. Furthermore, structural analysis and western blot revealed that SA upregulates protein kinase A (PKA) phosphorylation with competitive inhibition by a pan-PKA inhibitor, H89. SA binds to the adenosine triphosphate (ATP) site on the PKA catalytic subunit where H89 binds specifically. PKA-cat-α1 gene-silencing experiments confirmed that SA activates the thermogenic program via a mechanism involving PKA and cyclic AMP response element-binding protein (CREB) signaling. Moreover, SA treatment promoted lipolysis via a PKA/p38-mediated pathway. Our findings may allow us to open a new avenue of strategies against obesity and need further investigation.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.1
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• pp.179-184
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• 2014

Chemoresistance of breast cancer to doxorubicin is mediated mainly through activation of NF-kB and over expression of HER2. Curcumin and its analogues (PGV-0 and PGV-1) exert cytotoxic effects on T47D breast cancer cells. Suppression of NF-kB activation is suggested to contribute to this activity. The present study aimed to explore the effects of curcumin, PGV-0, and PGV-1 singly and in combination with doxorubicin on MCF-7/Dox cells featuring over-expression of HER2. In MTT assays, curcumin, PGV-0, and PGV-1 showed cytotoxicity effects against MCF-7/Dox with IC50 values of $80{\mu}M$, $21{\mu}M$, and $82{\mu}M$ respectively. These compounds increased MCF-7/Dox sensitivity to doxorubicin. Cell cycle distribution analysis exhibited that the combination of curcumin and its analogues with Dox increased sub G-1 cell populations. Curcumin and PGV-1 but not PGV-0 decreased localization of p65 into the nucleus induced by Dox, indicating that activation of NF-kB was inhibited. Molecular docking of curcumin, PGV-0, and PGV-1 demonstrated high affinity to HER2 at ATP binding site. This interaction were directly comparable with those of ATP and lapatinib. These findings suggested that curcumin, PGV-0 and PGV-1 enhance the Dox cytotoxicity to MCF-7 cells through inhibition of HER2 activity and NF-kB activation.

• Journal of Life Science
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• v.33 no.11
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• pp.876-886
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• 2023

In some cases of head and neck cancers (HNC), surgical interventions may result in the loss of organs and/or changes to their functions, thereby significantly affecting the patient's quality of life. As a result, the surgical treatment of HNC patients is often limited to specific cases, and alternative treatment modalities, such as chemotherapy, are considered. However, serious adverse effects caused by chemotherapy, such as severe nausea and vomiting, necessitate the need for the development of adjunctive methods to minimize patient suffering. Chuanxiong, Ligusticum chuanxiong (L. chuanxiong), is a natural herb used in Eastern medicine to treat cerebrovascular disorders and headaches. This study aimed to predict the effect and potential of L. chuanxiong as an auxiliary anticancer drug through network-based pharmacology and molecular docking analysis. The study results showed that 40 out of 41 genes of L. chuanxiong shared common targets of HNC and their proteins could be used to target HNC cells to prevent cancer progression. The results of the functional enrichment analysis confirmed that L. chuanxiong is associated with the neuroactive-ligand metabolism and neurotransmitter pathways, indicating its potential medicinal value as an adjuvant in HNC treatment. Lastly, our findings demonstrated that the active ingredient of L. chuanxiong, (Z)-Ligustilide, has the ATP binding site of heat shock protein 90, a protein known to promote the activation of cancer cells. These results suggest that L. chuanxiong is a promising candidate for developing auxiliary anticancer drugs, and further research could potentially lead to the discovery of newer and safer anti-cancer agents.