• Microbiology and Biotechnology Letters
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• v.38 no.4
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• pp.349-361
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• 2010

In this review, the current knowledge of the carbon metabolism and global carbon regulation in Corynebacterium glutamicum are summarized. C. gluamicum has phosphotransferase system (PTS) for the utilization of sucrose, glucose, and fructose. C. glutamicum does not show any preference for glucose when various sugars or organic acids are present with glucose, and thus cometabolizes glucose with other sugars or organic acids. The molecular mechanism of global carbon regulation such as carbon catabolite repression (CCR) in C. glutamicum is quite different to that in Gram-negative or low-GC Gram-positive bacteria. GlxR (glyoxylate bypass regulator) in C. glutamicum is the cyclic AMP receptor protein (CRP) homologue of E. coli. GlxR has been reported to regulate genes involved in not only glyoxylate bypass, but also central carbon metabolism and CCR including glycolysis, gluconeogenesis, and tricarboxylic acid (TCA) cycle. Therefore, GlxR has been suggested as a global transcriptional regulator for the regulation of diverse physiological processes as well as carbon metabolism. Adenylate cyclase of C. glutamicum is a membrane protein belonging to class III adenylate cyclases, thus it could possibly be a sensor for some external signal, thereby modulating cAMP level in response to environmental stimuli. In addition to GlxR, three additional transcriptional regulators like RamB, RamA, and SugR are also involved in regulating the expression of many genes of carbon metabolism. Finally, recent approaches for constructing new pathways for the utilization of new carbon sources, and strategies for enhancing amino acid production through genetic modification of carbon metabolism or regulatory network are described.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.241-241
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• 2008

Macrofore formation in silicon and other semiconductors using electrochemical etching processes has been, in the last years, a subject of great attention of both theory and practice. Its first reason of concern is new areas of macropore silicone applications arising from microelectromechanical systems processing (MEMS), membrane techniques, solar cells, sensors, photonic crystals, and new technologies like a silicon-on-nothing (SON) technology. Its formation mechanism with a rich variety of controllable microstructures and their many potential applications have been studied extensively recently. Porous silicon is formed by anodic etching of crystalline silicon in hydrofluoric acid. During the etching process holes are required to enable the dissolution of the silicon anode. For p-type silicon, holes are the majority charge carriers, therefore porous silicon can be formed under the action of a positive bias on the silicon anode. For n-type silicon, holes to dissolve silicon is supplied by illuminating n-type silicon with above-band-gap light which allows sufficient generation of holes. To make a desired three-dimensional nano- or micro-structures, pre-structuring the masked surface in KOH solution to form a periodic array of etch pits before electrochemical etching. Due to enhanced electric field, the holes are efficiently collected at the pore tips for etching. The depletion of holes in the space charge region prevents silicon dissolution at the sidewalls, enabling anisotropic etching for the trenches. This is correct theoretical explanation for n-type Si etching. However, there are a few experimental repors in p-type silicon, while a number of theoretical models have been worked out to explain experimental dependence observed. To perform ordered macrofore formaion for p-type silicon, various kinds of mask patterns to make initial KOH etch pits were used. In order to understand the roles played by the kinds of etching solution in the formation of pillar arrays, we have undertaken a systematic study of the solvent effects in mixtures of HF, N-dimethylformamide (DMF), iso-propanol, and mixtures of HF with water on the macrofore structure formation on monocrystalline p-type silicon with a resistivity varying between 10 ~ 0.01 $\Omega$ cm. The etching solution including the iso-propanol produced a best three dimensional pillar structures. The experimental results are discussed on the base of Lehmann's comprehensive model based on SCR width.

• Clean Technology
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• v.20 no.1
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• pp.13-21
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• 2014

Because of the water scarcity caused by the increase of salinity in the underground water, seawater desalination stands out as one of the most promising solution. As there are so much energy costs in operating desalination plants, new hybrid process which is more effective should be researched. A geothermal VMD (vacuum membrane distillation) hybrid process is a competitive alternative for seawater desalination. Because geothermal energy has significant characteristics of high capacity factor to operate the power plant at full capacity for 24 hour per day, it can be a priority heat source of VMD superior to any other renewable energies such as solar and wind power. In this study, we design a geothermal VMD hybrid process, analyze it economically and finally compare the result with a case of conventional VMD process. Geothermal VMD hybrid process generates $23,822,409 of NPV (net present value) more than the conventional VMD process in case of 5% discount rate. The break-even point between these processes is 5.36 year. Sensitivity analysis indicates that steam cost is the most decisive influence variable to the economic outcome.

• Applied Microscopy
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• v.29 no.1
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• pp.43-56
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• 1999

The relationship between intravascular erythroblasts and Kupffer cells in the human fetal liver from 11 to 20 week gestation was studied ultrastructurally. The walls of the developing sinusoids consisted of two cell types devoid of basal lamina, the nonfenestrasted endothelial cells and Kupffer cells. Kupffer cells examined were easily identified by their content of phagosmes and their morphological features, and partially proliferated by mitotic division which was different way of proliferation from adult. Some extruded nuclei of acidophilic erythroblasts were trapped within Kupffer cells which exhibited various stages of intracellular digestion of the nuclei. During high activity of human fetal hepatic erythropoiesis, Kupffer cells were found in association with developing erythrob-lasts, which was similar with erythroblastic islands. The developing erythroblasts were partially surrounded by multilaminated membrane system of the Kupffer cell consisting erythroblastic island, or in contact with Kupffer cell via cytoptasmic processes in the sinu-soidal lumen. The presence of these islands was confirmed by transmission and scanning electron microscopic study. The results demonstrate that Kupffer cells in fetal heaptic erythropoiesis phagocytized expelled nuclei and contributed to erythropoiesis mechanically and physiologically by the hypertrophy and the formation of erythroblastic islands.

• Journal of Life Science
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• v.22 no.3
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• pp.428-436
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• 2012

Protein phosphorylation is a universal mechanism that regulates cellular activities. The brassinosteroid (BR) signal transduction pathway is a relay of phosphorylation and dephosphorylation cascades. It starts with the BR-induced activation of the membrane receptor kinase brassinosteroid insensitive 1 (BRI1), resulting in the dephosphorylation of transcription factors such as BZR1/BES2 and BZR2/BES1 followed by BR-induced gene expression. Brassinosteroid signal transduction research has progressed rapidly by identifying the phosphorylation/dephosphorylation site(s) of the BR-regulated kinase and phosphatase substrates with a simultaneous pursuit of mutant phenotypes. Autophosphorylation, transphosphorylation, and serine/threonine and tyrosine phosphorylation of the receptor protein kinases BRI1 and BRI1-associated kinase (BAK1) have increased the understanding of the regulatory role of those kinases during physiological and developmental processes in plants. The phosphorylation event initiated by BR is also found in the regulation of receptor-mediated endocytosis and the subsequent degradation of the receptor. However, the basic molecular links of the BR signal transduction pathway are not well understood regarding this phosphorylation/dephosphorylation event. This review summarizes the current state of BR signal transduction research to uncover the phosphorylation/dephosphorylation networks and suggests directions for future research on steroid signal transduction to gain a more comprehensive understanding of the process.

• Journal of Life Science
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• v.29 no.2
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• pp.256-264
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• 2019

Lymphotoxin ${\beta}$ receptor ($LT{\beta}R$), a member of the tumor necrosis factor receptor family, plays an important role in lymphoid tissue's architecture and organogenesis. In contrast, MLCK and ROCK play critical roles in the regulation of stress fiber (SF) formation in cells. To determine whether $LT{\beta}R$ stimulation in fibroblastic reticular cells (FRCs) is involved in these signaling pathways, myosin light chain kinase inhibitor-7 (ML-7) was used to inhibit them. ML7-treated FRCs completely blocked SFs and showed retraction and shrinkage processes comparable to those observed in agonistic anti-$LT{\beta}R$ antibody-treated cells. The inhibition of ROCK activity with Y27632-induced changes in actin cytoskeleton organization and cell morphology in FRCs. Actin bundles rearranged into SFs, and phospho-myosin light chain (p-MLC) co-localized in FRCs. We checked the level of Rho-guanosine diphosphate (RhoGDP)/guanosine triphosphate (GTP) exchange activity using FRC lysate. When $LT{\beta}R$ was stimulated with agonistic anti-$LT{\beta}R$ antibodies, Rho-GDP/GTP exchange activity was markedly reduced. Regarding $LT{\beta}R$ signaling with a focus on MLCK inhibition, we showed that the phosphorylation of MLCs was reduced by $LT{\beta}R$ stimulation in FRCs. Cytoskeleton components, such as tubulin, b-actin, and phospho-ezrin proteins acting as membrane-cytoskeleton linkers, were produced in de-phosphorylation, and they reduced expression in agonistic anti-$LT{\beta}R$ antibody-treated FRCs. Collectively, the results suggested that MLCK and ROCK were simultaneously responsible for SF regulation triggered by $LT{\beta}R$ signaling in FRCs.

• Journal of Life Science
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• v.33 no.8
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• pp.651-662
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• 2023

Peroxisomes, known as microbodies, are a class of morphologically similar subcellular organelles commonly found in most eukaryotic cells. They are 0.2~1.8 ㎛ in diameter and are bound by a single membrane. The matrix is usually finely granular, but occasionally crystalline or fibrillary inclusions are observed. They characteristically contain hydrogen peroxide (H₂O₂) generating oxidases and contain the enzyme catalase, thus confining the metabolism of the poisonous H₂O₂ within these organelles. Therefore, the eukaryotic organelles are greatly dynamic both in morphology and metabolism. Plant peroxisomes, in particular, are associated with numerous metabolic processes, including β-oxidation, the glyoxylate cycle and photorespiration. Furthermore, plant peroxisomes are involved in development, along with responses to stresses such as the synthesis of important phytohormones of auxins, salicylic acid and jasmonic acids. In the past few decades substantial progress has been made in the study of peroxisome biogenesis in eukaryotic organisms, mainly in animals and yeasts. Advancement of sophisticated techniques in molecular biology and widening of the range of genomic applications have led to the identification of most peroxisomal genes and proteins (peroxins, PEXs). Furthermore, recent applications of proteome study have produced fundamental information on biogenesis in plant peroxisomes, together with improving our understanding of peroxisomal protein targeting, regulation, and degradation. Nonetheless, despite this progress in peroxisome development, much remains to be explained about how peroxisomes originate from the endoplasmic reticulum (ER), then assemble and divide. Peroxisomes perform dynamic roles in many phases of plant development, and in this review, we focus on the latest progress in furthering our understanding of plant peroxisome functions, biogenesis, and dynamics.

• Journal of Life Science
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• v.34 no.4
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• pp.279-285
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• 2024

The zonula occludens (ZO) protein serves as a scaffolding protein, providing structural support at the junctions between cells and the cytoplasmic surface. It acts as a bridge between integral membrane proteins and the cytoskeleton. Besides its structural role, it also participates in regulating cell growth and proliferation. Recent studies have highlighted the involvement of ZO protein in various diseases, including cancer. Specifically, research has indicated that ZO protein influences the cancer microenvironment surrounding cancer cells, thereby facilitating their growth and development. ZO proteins exert diverse functions in the cancer microenvironment, impacting processes such as angiogenesis, inflammatory responses, the epithelial-mesenchymal transition, and interactions with mesenchymal stem cells. The specific mechanisms vary depending on the type of cancer and environmental conditions. Recent research unveiled several signaling pathways involving ZO protein, which could potentially impede cancer progression in the tumor microenvironment. Consequently, these insights open avenues for novel treatment strategies. While the numerous physiological, structural, and morphological roles of ZO protein have been observed at the cellular and in vivo levels, understanding the signaling mechanisms it operates in vivo and how these mechanisms influence the cancer microenvironment remains a challenge. In this review, we delineate the characteristics and regulatory mechanisms of ZO protein in the context of the cancer microenvironment. Additionally, we propose leveraging the properties of ZO protein to devise defense mechanisms within the cancer cell environment and provide an overview of its in vivo role.

• Tuberculosis and Respiratory Diseases
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• v.87 no.4
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• pp.494-504
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• 2024

Background: Ubiquitin C-terminal hydrolase L1 (UCHL1), which encodes thiol protease that hydrolyzes a peptide bond at the C-terminal glycine residue of ubiquitin, regulates cell differentiation, proliferation, transcriptional regulation, and numerous other biological processes and may be involved in lung cancer progression. UCHL1 is mainly expressed in the brain and plays a tumor-promoting role in a few cancer types; however, there are limited reports regarding its role in lung cancer. Methods: Single-cell RNA (scRNA) sequencing using 10X chromium v3 was performed on a paired normal-appearing and tumor tissue from surgical specimens of a patient who showed unusually rapid progression. To validate clinical implication of the identified biomarkers, immunohistochemical (IHC) analysis was performed on 48 non-small cell lung cancer (NSCLC) tissue specimens, and the correlation with clinical parameters was evaluated. Results: We identified 500 genes overexpressed in tumor tissue compared to those in normal tissue. Among them, UCHL1, brain expressed X-linked 3 (BEX3), and midkine (MDK), which are associated with tumor growth and progression, exhibited a 1.5-fold increase in expression compared to that in normal tissue. IHC analysis of NSCLC tissues showed that only UCHL1 was specifically overexpressed. Additionally, in 48 NSCLC specimens, UCHL1 was specifically upregulated in the cytoplasm and nuclear membrane of tumor cells. Multivariable logistic analysis identified several factors, including smoking, tumor size, and high-grade dysplasia, to be typically associated with UCHL1 overexpression. Survival analyses using The Cancer Genome Atlas (TCGA) datasets revealed that UCHL1 overexpression is substantially associated with poor survival outcomes. Furthermore, a strong association was observed between UCHL1 expression and the clinicopathological features of patients with NSCLC. Conclusion: UCHL1 overexpression was associated with smoking, tumor size, and high-grade dysplasia, which are typically associated with a poor prognosis and survival outcome. These findings suggest that UCHL1 may serve as an effective biomarker of NSCLC.

• Applied Chemistry for Engineering
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• v.35 no.5
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• pp.410-417
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• 2024

Steel mill gases, including coke oven gas (COG), blast furnace gas (BFG), and Linz-Donawitz gas (LDG), are mainly used as fuels within steel plants, resulting in substantial CO₂ emissions. This combustion process accounts for 10% of South Korea's total CO₂ emissions. These off-gases, rich in CO, CH₄, and hydrogen, have the potential to be converted into valuable chemicals through catalytic processes, thereby reducing CO₂ emissions and increasing their economic value. This study investigates the conversion of steel mill gases into methanol, an important platform chemical and cleaner transportation fuel. By using COG and LDG as sources of CO and H₂, respectively, a novel process was developed. In this process, H₂-rich COG from a simple single-step membrane separation and raw LDG are converted into methanol with high selectivity using a Cu-Zn-Al catalyst. The study identified the optimal gas compositions for methanol production through experimental results, demonstrating efficient methanol synthesis from various compositions of LDG, COG, pure hydrogen, and H₂-rich COG. This innovative approach not only aims to reduce specific CO₂ emissions from steel plants but also enhances the economic value of the byproduct gases. Thus, the study provides a sustainable and economically advantageous solution for the steel industry.