• Korean Journal of Food Science and Technology
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• v.45 no.6
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• pp.801-804
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• 2013

The glutathione contents of the selected mutants were investigated and found to be 6.1-15.8 mg/g-DCW. The glutathione content positively correlated with the antioxidant activity of the mutant strains ($R^2$=0.488). Furthermore, the glutathione content of the mutant S. cerevisiae Sa-59 was approximately 38% greater than that of the wild type strain and, therefore, this mutant strain was selected for glutathione production. The volumetric glutathione content in a shaking culture was increased by about 70% compared to the static culture. In addition, the specific glutathione content was increased by ~19%. The volumetric glutathione content and specific glutathione content were increased by approximately 16% and 66%, respectively, when 0.04% glutamate, 0.04% cysteine and 0.04% glycine were added. Furthermore, the highest antioxidant activity was 0.52 as absorbance unit at 700 nm.

• Journal of Microbiology and Biotechnology
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• v.13 no.2
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• pp.263-268
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• 2003

Recently, we identified a domain, termed MIRC3-4, for the protein-protein interaction between yeast chitin synthase 3 (CHS3) and chitin synthase 4 (CHS4). In this study, the functional roles of MIRC3-4 were examined at the G1 phase and cytokinesis of the cell cycle by Calcofluor staining and FISH. Some mutations in MIRC3-4 resulted in disappearance of the chitin ring in the early G1 phase, but did not affect chitin synthesis in the cell wall at cytokinesis. The chitin distribution in chs4 mutant cells indicated that CHS4 was involved in the synthesis of chitinring in the G1 phase and in the synthesis of cell wall chitin after cytokinesis, suggesting that Chs4p regulates chitin synthase 3 activity differently in G1 and cytokinesis. Absence of the chitin ring could be caused either by delocalization of Chs3p to the bud-neck or by improper interaction with Chs4p. When mutant cells were immunostained with a Chs3p-specific antibody to discriminate between these two alternatives, the mutated Ch3p was found to localize to the neck in all MIRC3-4 mutants. These results strongly irdicate that Chs4p regulates Chs3p as an activator but not a recruiter.

• Microbiology and Biotechnology Letters
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• v.45 no.1
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• pp.51-56
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• 2017

Cellulosic biomass is a renewable source for biofuel production from non-edible biomass. An optimized pretreatment process is required for the efficient utilization of cellulosic biomass. Among various pretreatment processes, the use of ionic liquids has been reported recently. However, the residual ionic liquid after pretreatment acts as an inhibitor of microbial fermentation. Recently, we isolated mutant Saccharomyces cerevisiae strains resistant to the ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIM][Ac]) by using a directed evolutionary approach. When 3% [EMIM][Ac] was added to a medium containing 80 g/l of glucose, mutants D452-B2 and D452-S3 produced 35.6 g/l and 36.3 g/l of ethanol, respectively, for 18 h while the parental strain (S. cerevisiae D452-2) produced 1.3 g/l of ethanol. Thus, these mutant S. cerevisiae strains might prove advantageous when ionic liquids are used for biofuel production from cellulosic biomass.

• Proceedings of the Microbiological Society of Korea Conference
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• 2000.10a
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• pp.39-45
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• 2000

It hab been proposed that CHS3-mediated chitin synthesis during the vegitative cell cycle is regulated by CHS4. To investigate direct protein-protein interaction between their coding products, we used yeast two hybrid system and found that a domain of Chs3p was responsible for interaction with Chs4p. This domain, termed MIRC3-4 (maximum interacting region of chs3p with chs4p), spans from 647 to 700 residues. It is well conserved among CHS3 homologs of various fungi such as Candida albicans, Emericella nidulans, Neurospora crassa, Magnaporthe grisea, Ustilago maydis, Glomus versiforme, Exophiala dermatitidis, Rhizopus microsporus. A series of mutaion in the MIRC3-4 resulted in no appearance of chitin ring at the early G 1 phase but did not affect chitin synthesis in the cell wall after cytokinesis. Absence of chitin ring could be caused either by delocalization of Chs3p to the septum or by improper interaction with Chs4p. To discriminate those two, not mutually exclusive, alternatives, mutants cells were immunostained with Chs3p-specific antibody. Some exhibited localization of chs3p to the septum, while others failed. These results indicate that simultaneous localization and activation Chs3p by Chs4p is required for chitin ring synthesis.

• Korean Journal of Microbiology
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• v.45 no.4
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• pp.300-305
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• 2009

We constructed the deletion mutants of fission yeast Schizosaccharomyces pombe spNab2 gene that is homologous to poly(A)-binding protein NAB2 in budding yeast Saccharomyces cerevisiae, which plays crucial roles in mRNA 3' end formation and mRNA export from nucleus into the cytoplasm. A null mutant in an $h^+$/ $h^+$ diploid strain was constructed by replacing the spNab2-coding region with an $ura4^+$ gene using one-step gene disruption method. Tetrad analysis showed that the spNab2 is not essential for vegetative growth and mRNA export. However, over-expression of spNab2 cause the severe growth defects and intensive accumulation of poly(A) RNA in the nucleus. Also, the spNab2-GFP fusions were localized mainly in the nucleus. These results suggest that spNab2 is also involved in mRNA export out of the nucleus.

• Molecules and Cells
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• v.39 no.7
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• pp.550-556
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• 2016

During meiosis, exchange of DNA segments occurs between paired homologous chromosomes in order to produce recombinant chromosomes, helping to increase genetic diversity within a species. This genetic exchange process is tightly controlled by the eukaryotic RecA homologs Rad51 and Dmc1, which are involved in strand exchange of meiotic recombination, with Rad51 participating specifically in mitotic recombination. Meiotic recombination requires an interaction between homologous chromosomes to repair programmed double-strand breaks (DSBs). In this study, we investigated the budding yeast meiosis-specific proteins Hop2 and Sae3, which function in the Dmc1-dependent pathway. This pathway mediates the homology searching and strand invasion processes. Mek1 kinase participates in switching meiotic recombination from sister bias to homolog bias after DSB formation. In the absence of Hop2 and Sae3, DSBs were produced normally, but showed defects in the DSB-to-single-end invasion transition mediated by Dmc1 and auxiliary factors, and mutant strains failed to complete proper chromosome segregation. However, in the absence of Mek1 kinase activity, Rad51-dependent recombination progressed via sister bias in the $hop2{\Delta}$ or $sae3{\Delta}$ mutants, even in the presence of Dmc1. Thus, Hop2 and Sae3 actively modulate Dmc1-dependent recombination, effectively progressing homolog bias, a process requiring Mek1 kinase activation.

• Journal of Microbiology and Biotechnology
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• v.28 no.12
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• pp.1982-1991
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• 2018

Ethanol accumulation inhibited the growth of Saccharomyces cerevisiae during wine fermentation. Autophagy and the release of reactive oxygen species (ROS) were also induced under ethanol stress. However, the relation between autophagy and ethanol stress was still unclear. In this study, expression of the autophagy genes ATG1 and ATG8 and the production of ROS under ethanol treatment in yeast were measured. The results showed that ethanol stress very significantly induced expression of the ATG1 and ATG8 genes and the production of hydrogen peroxide ($H_2O_2$) and superoxide anion (${O_2}^{{\cdot}_-}$). Moreover, the atg1 and atg8 mutants aggregated more $H_2O_2$ and ${O_2}^{{\cdot}_-}$ than the wild-type yeast. In addition, inhibitors of the ROS scavenging enzyme induced expression of the ATG1 and ATG8 genes by increasing the levels of $H_2O_2$ and ${O_2}^{{\cdot}_-}$. In contrast, glutathione (GSH) and N-acetylcystine (NAC) decreased ATG1 and ATG8 expression by reducing $H_2O_2$ and ${O_2}^{{\cdot}_-}$ production. Rapamycin and 3-methyladenine also caused an obvious change in autophagy levels and simultaneously altered the release of $H_2O_2$ and ${O_2}^{{\cdot}_-}$. Finally, inhibitors of the mitochondrial electron transport chain (mtETC) increased the production of $H_2O_2$ and ${O_2}^{{\cdot}_-}$ and also promoted expression levels of the ATG1 and ATG8 genes. In conclusion, ethanol stress induced autophagy which was regulated by $H_2O_2$ and ${O_2}^{{\cdot}_-}$ derived from mtETC, and in turn, the autophagy contributed to the elimination $H_2O_2$ and ${O_2}^{{\cdot}_-}$.

• Korean Journal of Microbiology
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• v.35 no.4
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• pp.258-265
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• 1999

Entry into meiosis in the yeast Saccharomyces cerevisiae is regulated by two major factors: the cell type MATa/MAT${\alpha}$ and the nutriational state (starvation) of the cell. The two independent regulations act through IME1and IME2 expression to initiate meiosis. IME2 encodes a meiosis-specific protein kinase, and it enabled MATa/MAT${\alpha}$ diploid cells to undergo meiosis and sporulation. The PCR mutagenesis method was applied for the isolation of thermosensitive ime2 mutants. Among sixty two mutants isolated from the phenotype of defective spore formation under the restrictive temperature, three with the most easily observed temperature-sensitive phenotype (ts ${\cdot}$ime2-11, ts ${\cdot}$ime2-12 and ts ${\cdot}$ime2-13) were selected for further study. To understand the detailed functions of IME2, we examined the defects of these mutants in the early meiotic pathway including the premeiotic DNA replication and exhibited decreased level in meiotic recombination. These results suggest that the IME2 gene plays essential role in meiotic recombination pathway as well as premeiotic DNA replication. As the result of the IME2 overexpression in ${\Delta}$mre4. moreover, it was suggested that the IME2 and MRE4 genes act on the same pathway of initiation step in meiotic recombination.

• Korean Journal of Microbiology
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• v.54 no.4
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• pp.309-319
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• 2018

Previously, six Schizosaccharomyce pombe mutants that induce pheromone even in the presence of nitrogen source were isolated from a bank of temperature sensitive mutants. In this report, one of these mutants, pws6 was further characterized. The pheromone induction in pws6 mutant cells was specific to nutrient: the M-factor pheromone was induced without nitrogen starvation but not without glucose starvation. This result suggests that the pws6 mutant might have a specific defect in the pathway for nitrogen starvation. The pws6 mutant induces P-factor pheromone as well as M-factor without starvation of nitrogen in temperature sensitive mode, suggesting that the pheromone induction phenotype of pws6 mutation is not cell-type specific. From cloning of the $pws6^+$ gene by complementation of the temperature sensitive growth defect, three plasmids containing 8.1 kb, 3.3 kb, and 4.8 kb yeast DNA were recovered. These plasmids complement the growth defect of the pws6 mutant by 100%, 70%, and 10~20%, respectively. The abilities of these plasmids to complement pheromone induction phenotype of pws6 mutant cells were correlated well with the efficiencies of complementation of the growth defect. With comparison of their open reading frames to the complementation efficiencies, it is concluded that the open reading frame, SPBC19C7.06 is responsible for the complementation of temperature sensitive phenotype of the pws6 mutant. This open reading frame, named prs1, contains one long exon with no intron and encodes a putative prolyl tRNA synthetase. The putative Prs1 protein exhibits significant similarities to the prolyl tRNA synthetases of other species.

• BMB Reports
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• v.31 no.4
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• pp.307-327
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• 1998

Cytochrome c peroxidase (CcP) is a yeast mitochondrial enzyme which catalyzes the reduction of hydrogen peroxide to water using two equivalents of ferrocytochrome c. The CcP/cytochrome c system has many features which make it a very useful model for detailed investigation of heme protein structure/function relationships including activation of hydrogen peroxide, protein-protein interactions, and long-range electron transfer. Both CcP and cytochrome c are single heme, single subunit proteins of modest size. High-resolution crystallographic structures of both proteins, of one-to-one complexes of the two proteins, and a number of active-site mutants are available. Site-directed mutagenesis studies indicate that the distal histidine in CcP is primarily responsible for rapid utilization of hydrogen peroxide implying significantly different properties of the distal histidine in the peroxidases compared to the globins. CcP and cytochrome c bind to form a dynamic one-to-one complex. The binding is largely electrostatic in nature with a small, unfavorable enthalpy of binding and a large positive entropy change upon complex formation. The cytochrome c-binding site on CcP has been mapped in solution by measuring the binding affinities between cytochrome c and a number of CcP surface mutations. The binding site for cytochrome c in solution is consistent with the crystallographic structure of the one-to-one complex. Evidence for the involvement of a second, low-affinity cytochrome c-binding site on CcP in long-range electron transfer between the two proteins is reviewed.