• Molecules and Cells
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• v.38 no.2
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• pp.180-186
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• 2015

Escherichia coli AcrAB-TolC is a multidrug efflux pump that expels a wide range of toxic substrates. The dynamic nature of the binding or low affinity between the components has impeded elucidation of how the three components assemble in the functional state. Here, we created fusion proteins composed of AcrB, a transmembrane linker, and two copies of AcrA. The fusion protein exhibited acridine pumping activity, suggesting that the protein reflects the functional structure in vivo. To discern the assembling mode with TolC, the AcrBA fusion protein was incubated with TolC or a chimeric protein containing the TolC aperture tip region. Three-dimensional structures of the complex proteins were determined through transmission electron microscopy. The overall structure exemplifies the adaptor bridging model, wherein the funnel-like AcrA hexamer forms an intermeshing cogwheel interaction with the ${\alpha}$-barrel tip region of TolC, and a direct interaction between AcrB and TolC is not allowed. These observations provide a structural blueprint for understanding multidrug resistance in pathogenic Gram-negative bacteria.

• Molecules and Cells
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• v.27 no.2
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• pp.183-190
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• 2009

The plasma membrane-localized BRASSINOSTEROID-INSENSITIVE1 (BRI1) and BRI1-ASSOCIATED KINASE1 (BAK1) are a well-known receptor pair involved in brassinosteroids (BR) signaling in Arabidposis. The formation of a receptor complex in response to BRs and the subsequent activation of cytoplasmic domain kinase activity share mechanistic characteristics with animal receptor kinases. Here, we demonstrate that BRI1 and BAK1 are BR-dependently phosphorylated, and that phosphorylated forms of the two proteins persist for different lengths of time. Mutations of either protein abolished phosphorylation of the counterpart protein, implying transphosphorylation of the receptor kinases. To investigate the specific amino acids critical for formation of the receptor complex and activation of BAK1 kinase activity, we expressed several versions of BAK1 in yeast and plants. L32E and L46E substitutions resulted in a loss of binding of BAK1 to BRI1, and threonine T455 was essential for the kinase activity of BAK1 in yeast. Transgenic bri1 mutant plants overexpressing BAK1(L46E) displayed reduced apical dominance and seed development. In addition, transgenic wild type plants overexpressing BAK1(T455A) lost the phosphorylation activity normally exhibited in response to BL, leading to semi-dwarfism. These results suggest that BAK1 is a critical component regulating the duration of BR efficacy, even though it cannot directly bind BRs in plants.

• The Korean Journal of Physiology and Pharmacology
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• v.12 no.5
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• pp.225-230
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• 2008

Netrins are secreted molecules and involved in axon guidance, cell migration and tumor development. Recent studies revealed that netrins perform novel functions in such processes as epithelial development and angiogenesis without operating through the classical netrin receptors, DCC (Deleted in Colorectal Cancer) and Unc5h. In the present study, we investigated the roles of netrin-1 and its receptors in cell spreading of human glioblastoma cells, and found that netrin-1 haptotactically enhanced fibronectin-induced cell spreading and focal adhesion formation in U373 glioblastoma cells. Netrin-1 binding to the U373 cell membrane was blocked by an antibody against ${\alpha}v$ integrin subunit, but not by an anti-DCC or anti-Unc5h antibody. In addition, enhancement of the fibronectin response by netrin-1 was abrogated by a function blocking antibody against integrin ${\alpha}v{\beta}3$. Since the ${\alpha}v$ subunit of the integrin family plays an important role in the pathophysiological aspects of cell migration, including tumor angiogenesis and metastasis, our data provide important insight into the molecular mechanism of netrin function.

• Journal of the Korean Magnetic Resonance Society
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• v.21 no.2
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• pp.72-77
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• 2017

${\beta}-catenin$ is a key signaling protein which regulates cell signaling and gene transcription. Abnormal activation of ${\beta}-catenin$ is linked to many cancers, particularly with colorectal cancers. Although many genetic and biological studies on $Wnt/{\beta}-catenin$ have been reported and structures of the complex between ${\beta}-catenin$ and its diverse binding partners have been published, many of them have focused on armadillo repeat domain of ${\beta}-catenin$. Both N- and C-terminal domains have been suggested to regulate interactions of ${\beta}-catenin$ with other molecules, but still little is known about the C-terminal unstructured domain. To investigate the structure of this domain, construct of C-terminus was designed and structural studies were performed using size exclusion chromatography (SEC), circular dichroism (CD), fluorescence and nuclear magnetic resonance (NMR) spectroscopy. We observed that not only the purified full-length construct but the purified C-terminal construct also dimerizes in solution by SEC, suggesting that this domain involves in dimerization of ${\beta}-catenin$. CD and fluorescence data indicate its flexibility and structural formation in the presence of membrane environments.

• Journal of Oriental Neuropsychiatry
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• v.19 no.1
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• pp.43-54
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• 2008

Objective: The aim of this study is to evaluate the anticonvulsive effects of Gamiheichumhwan extract and to explain its action in GABAergic neuromodulation of the rat brain. Method: The extracts of Gamiheichumhwan were investigated for their inhibitory effect on GABA transaminase activity, their influence on brain GABA and glutamate levels, their agonistic activity on GABA/benzodiazepine receptor and anticonvulsive action using in vitro and in vivo assays. Results: 1. The extract inhibited dose-dependently GABA transaminase (GABA-T) activity by 4.6% and 18.9%, respectively at dosages of 250 mg/kg and 500mg/kg mouse (p.o.). 2. Brian GABA level was increased to 72.0% and brain glutamate level was decreased to 9.6% at a dosage of 500 mg/kg mouse (p.o.). 3. The extract suppressed [3H]Ro15-1788 binding to rat cerebral cortical membrane by $81.4{\pm}0.8%$ at a dosage of 3.2 mg, suggesting its agonistic activity on GABA/benzodiazepin receptor. 4. The extract showed anticonvulsive effect by lengthening the onset time of convulsion, shortening the convulsion duration and diminishing the lethality. Conclusion : It is suggested that Gamiheichumhwan can be used to somnipathy and adapted to treatment and prevention of epilepsy or convulsion.

• Biomolecules & Therapeutics
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• v.2 no.4
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• pp.303-309
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• 1994

The analysis of membrane receptors for hormones and neurotransmitters has progressed considerably by pharmacological and biochemical means and more recently through the use of specific antibodies. Two kinds of antibodies could be produced, one is from synthetic peptides and the other from proteins such as purified receptor. Anti-peptide antibodies gave some advantages; epitope is evident and also receptor purification in quantity is not prerequisite. It can be also applied to the study of receptor structure-activity relationship. The purpose of the present study was 1) to produce and characterize a polyclonal antibody against a synthetic $\beta$2-adrenergic receptor peptide(Phe-Gly-Asn-Phe-Trp-Cys-Phe-Trp-Thr-Ser-Ile-Asp-Val-Leu) and 2) to determine the effects of this antibody on the $\beta$-adrenergic receptor ligand interaction. The peptide sequence contains an amino acid residue such as Asp-113 which was identified as one of important component for receptor-ligand interaction in site-directed mutagenesis studies. Production of antibody was performed by immunization of rabbits through popliteal lymph node with the peptide coupled with Keyhole Limpet Hemocyanin (KLH). The titer of antibody against this peptide was 1 : 1000. The anti-peptide antibody was able to detect a 67 kDa protein band in western blot corresponding to the molecular weight of the $\beta$-adrenergic receptor in partially purified receptor fraction derived from guinea pig lung. The antisera inhibited the specific binding of [$^3$H]dihydroalprenolol to $\beta$-adrenergic receptor in a concentration-dependent manner. The results from this study suggest that the peptide sequence selected in the present study is important for the receptor ligand interaction.

• Herbal Formula Science
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• v.29 no.4
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• pp.167-179
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• 2021

Objectives : Oxidative stress is a important cause of liver disease, and regulation of oxidative stress is essential to maintain the normal metabolic function of the liver. Until a recent date, there has been no studies on the hepatoprotective effect of Ikwiseungyang-tang (IWSYT). Therefore, this study aims to demonstrate the hepatoprotective effect of IWSYT and its related molecular mechanisms on arachidonic acid (AA) + iron induced oxidative stress model in HepG2 cells. Methods : To determine the cytoprotective effect of IWSYT against AA + iron-induced oxidative stress, cell viability, apoptosis-related proteins, intracellular reactive oxygen species (ROS), GSH, and mitochondrial membrane potential (MMP) were measured. Nuclear factor erythroid 2-related factor 2 (Nrf2) activation was analyzed by immunoblot analysis. In addition, Nrf2 transcription activation through ARE binding was measured by reporter gene assays, and the expression of the Nrf2 target antioxidant genes were confirmed by immunoblot analysis. Results : IWSYT increased cell viability from cell death induced by AA + Iron, and inhibited apoptosis by regulating apoptosis-related proteins. Furthermore, IWSYT protected cells by inhibiting intracellular ROS production, GSH depletion, and MMP degradation. Nrf2 activation was increased by IWSYT, and Nrf2 target genes were activated by IWSYT too. Conclusions : These results suggest that IWSYT can protect hepatocytes from oxidative stress through Nrf2 activation and can be potentially applied in the prevention and treatment of liver damage.

• ALGAE
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• v.36 no.4
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• pp.315-326
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• 2021

Ion channels are membrane protein complexes mediating passive ion flux across the cell membranes. Every organism has a certain set of ion channels that define its physiology. Dinoflagellates are ecologically important microorganisms characterized by effective physiological adaptability, which backs up their massive proliferations that often result in harmful blooms (red tides). In this study, we used a bioinformatics approach to identify homologs of known ion channels that belong to 36 ion channel families. We demonstrated that the versatility of the dinoflagellate physiology is underpinned by a high diversity of ion channels including homologs of animal and plant proteins, as well as channels unique to protists. The analysis of 27 transcriptomes allowed reconstructing a consensus ion channel repertoire (channelome) of dinoflagellates including the members of 31 ion channel families: inwardly-rectifying potassium channels, two-pore domain potassium channels, voltage-gated potassium channels (K_v), tandem K_v, cyclic nucleotide-binding domain-containing channels (CNBD), tandem CNBD, eukaryotic ionotropic glutamate receptors, large-conductance calcium-activated potassium channels, intermediate/small-conductance calcium-activated potassium channels, eukaryotic single-domain voltage-gated cation channels, transient receptor potential channels, two-pore domain calcium channels, four-domain voltage-gated cation channels, cation and anion Cys-loop receptors, small-conductivity mechanosensitive channels, large-conductivity mechanosensitive channels, voltage-gated proton channels, inositole-1,4,5-trisphosphate receptors, slow anion channels, aluminum-activated malate transporters and quick anion channels, mitochondrial calcium uniporters, voltage-dependent anion channels, vesicular chloride channels, ionotropic purinergic receptors, animal volage-insensitive cation channels, channelrhodopsins, bestrophins, voltage-gated chloride channels H⁺/Cl^- exchangers, plant calcium-permeable mechanosensitive channels, and trimeric intracellular cation channels. Overall, dinoflagellates represent cells able to respond to physical and chemical stimuli utilizing a wide range of G-protein coupled receptors- and Ca²⁺-dependent signaling pathways. The applied approach not only shed light on the ion channel set in dinoflagellates, but also provided the information on possible molecular mechanisms underlying vital cellular processes dependent on the ion transport.

• Journal of Veterinary Science
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• v.22 no.2
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• pp.15.1-15.13
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• 2021

Background: Attenuated Salmonella strain can be used as a vector to transport immunogens to the host antigen-binding sites. Objectives: The study aimed to determine the protective efficacy of attenuated Salmonella strain expressing highly conserved Brucella immunogens in goats. Methods: Goats were vaccinated with Salmonella vector expressing individually lipoprotein outer-membrane protein 19 (Omp19), Brucella lumazine synthase (BLS), proline racemase subunit A (PrpA), Cu/Zn superoxide dismutase (SOD) at 5 × 10⁹ CFU/mL and challenge of all groups was done at 6 weeks after vaccination. Results: Among these vaccines inoculated at 5 × 10⁹ CFU/mL in 1 mL, Omp19 or SOD showed significantly higher serum immunoglobulin G titers at (2, 4, and 6) weeks post-vaccination, compared to the vector control. Interferon-γ production in response to individual antigens was significantly higher in SOD, Omp19, PrpA, and BLS individual groups, compared to that in the vector control (all p < 0.05). Brucella colonization rate at 8 weeks post-challenge showed that most vaccine-treated groups exhibited significantly increased protection by demonstrating reduced numbers of Brucella in tissues collected from vaccinated groups. Real-time polymerase chain reaction revealed that Brucella antigen expression levels were reduced in the spleen, kidney, and parotid lymph node of vaccinated goats, compared to the non-vaccinated goats. Besides, treatment with vaccine expressing individual antigens ameliorated brucellosis-related histopathological lesions. Conclusions: These results delineated that BLS, Omp19, PrpA, and SOD proteins achieved a definite level of protection, indicating that Salmonella Typhimurium successfully delivered Brucella antigens, and that individual vaccines could differentially elicit an antigen-specific immune response.

• Food Engineering Progress
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• v.21 no.1
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• pp.1-11
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• 2017

Dyslipidemia, defined as elevated triglyceride (TG), total- and LDL-C, and/or decreased HDL-C levels, is considered a principal risk factor for cardiovascular disease. The low-density lipoprotein receptor (LDLR) family has been considered a key player in the prevention of dyslipidemia. The LDLR family consists of cytoplasmic membrane proteins and plays an important role not only in ligand-receptor binding and uptake, but also in various cell signaling pathways. Emerging reports state that various functional ingredients dynamically modulate the function of the LDLR family. For instance, oats stimulated the LDLR function in vivo, resulting in decreased body weight and improved serum lipid profiles. The stimulation of LRP6 by functional ingredients in vitro activated the Wnt/${\beta}-catenin$ pathway, subsequently suppressing the intracellular TG via inhibition of SREBP1, $PPAR{\gamma}$, and $C/EBP{\alpha}$. Furthermore, the extract of Cistanchetubulosa enhanced the expression of the mRNA of VLDLR, followed by a reduction in the serum cholesterol level. In addition, fermented soy milk diminished TG and total cholesterol levels while increasing HDL-C levels via activation of LRP1. To summarize, modulating the function of the LDLR family by diverse functional ingredients may be a potent therapeutic remedy for the treatment of dyslipidemia and cardiovascular diseases.