• Preventive Nutrition and Food Science
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• v.9 no.2
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• pp.187-189
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• 2004

To isolate a mutant strain which overproduces tryptophan, mutants of Candida rugosa were screened after EMS (ethyl methane sulfonate) mutagenesis. Fluorotryptophan, a tryptophan analogue, was used for selection of a tryptophan-overproducing mutant after mutagenesis. Among 50 mutants, several candidates were selected based on intracellular tryptophan content. Amino acid analysis results showed that C3 was the best strain because it had the highest amount of tryptophan among the mutants.

• Preventive Nutrition and Food Science
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• v.2 no.2
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• pp.155-161
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• 1997

The mutagenic and antimutagenic activities of juices from 20 common edible wild herbs found in Korea were investigated using the spore-rec assay and Ames test. The juices of Hemerocallis fulva and Capsella bursapastoris exhibited a little induction or inhibition of mutagenesis in the presence of selected metal ions, but juices of most edible wild herbs did not affect on the mutagenesis in the spore-rec assay. In the other hand, all of the juices strongly inhibited the mutagenesis induced by benzo[a]pyrene, 2-amino-fluorene, and 3-amino-1,4-dimethyl-5H-pyridol tested on Salmonella typhimurium TA98 or TA100 in the presence of S-9 mix. The antimutagenic effects increased as the concentration of the mutagens increase. The results suggest that concentration of samples or types of various mutagen interact to affect the antimutagenic potential of the juices in the TA98 and TA100 strain.

• Journal of the Korean Chemical Society
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• v.64 no.4
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• pp.225-230
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• 2020

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3515-3516
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• 2010

• Proceedings of the Korean Society of Life Science Conference
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• 2007.10a
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• pp.107.1-107.1
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• 2007

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• Biotechnology and Bioprocess Engineering:BBE
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• v.7 no.5
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• pp.311-315
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• 2002

By the in vitro combinatorial mutagenesis, which is a sequential reaction of PCR mutagenesis and in vitro coupled transcription/translation with Escherichia coli S30 extract, S65 and E222 of green fluorescent protein of Aequarea victoria were comprehensively changed to all possible combinations of amino acids, thus totally 400 mutant (including a wild type) proteins were simultaneously produced and their fluorescent properties were analyzed. Although a few mutations had been reported so far at the 222nd position, replacement E222 to all other19 amino acids gave fluorescent signal to the mutants by changing Ser 65 to Ala together. Among the mutants, replacement to G, A, S, Q, H and C gave relatively high fluorescence. The in vitro combinatorial mutagenesis, therefore, has been proved valuable for comprehensive structure-function studies of proteins.

• Journal of Microbiology
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• v.37 no.3
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• pp.154-158
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• 1999

The arginine residue at position 243 (Arg 243) of the yeast transcription factor, Gcn4p, is invariably conserved among bZIP transcription factors. Using site-directed oligonucleotide saturation mutagenesis involving two-step polymerase chain reaction (PCR) amplification, random mutations were successfully introduced at the codon of 243 in the basic domain of Gcn4p. This mutant library was transformed ito Gcn4p defective yeast strain and selected for the transcriptionally active colonies. All colonies which were transcriptionally active had arginines in the codon 243. In this study, the strand preference by Taq polymerase during mutagenesis was also tested. Oligonucleotides were specially designed to test whether or not the polymerase was preferred using the strand as a template. A population of randomly mutated products were cloned into an appropriate vector and characterized by DNA sequencing analysis. Saturation mutagenesis which was performed efficiently by this method revealed a strong bias in terms of strand preference of Taq polymerase by an approximate ratio of 3 to 1 in this study.

• Biomedical Science Letters
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• v.14 no.2
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• pp.119-122
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• 2008

The baculovirus/insect cell expression system is of great value in the study of structure-function relationships in mammalian glucose-transport proteins by site-directed mutagenesis and for the large-scale production of these proteins for mechanistic and biochemical studies. In order to exploit this, the effects of substitution at the highly conserved residue glutamine 282 of the human erythrocyte-type glucose transporter have been examined by in vitro site-directed mutagenesis. The modified human transport protein has been expressed in Spodoptera frugiperda 21 cells by using the recombinant baculovirus AcNPV-GTL. To assess the functional integrity of the expressed transporter, measurements of the transport inhibitor cytochalasin B binding were performed, involving the membranes prepared from 4 days post infection with no virus, with wild-type virus or AcNPV-GTL virus. Data obtained showed that there was little or no D-glucose-inhibitable binding in cells infected with the wild type or no virus. Only the recombinant virus infected cells exhibited specific binding, which is inhibitable by D- but not by L-glucose. However, there was a notable reduction in the affinity for the potent inhibitor cytochalasin B when binding measurements of AcNPV-GTL were compared with those of AcNPV-GT, which has no substitution. It is thus suggested that although the modified and unmodified human transporters differed slightly in their affinity for cytochalasin B, the glutamine substitution did not interfere the heterologous expression of the human transporter in the insect cells.

• BMB Reports
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• v.37 no.1
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• pp.122-132
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• 2004

The rapid development and characterization of the mouse genome sequence, coupled with comparative sequence analysis of human, has been paralleled by a reinforced enthusiasm for mouse functional genomics. The way to uncover the in vivo function of genes is to analyze the phenotypes of the mutant animals. From this standpoint, the mouse is a suitable and valuable model organism in the studies of functional genomics. Therefore, there have been enormous efforts to enrich the list of the mutant mice. Such a trend emphasizes the random mutagenesis, including ENU mutagenesis and gene-trap mutagenesis, to obtain a large stock of mutant mice. However, since various mutant alleles are needed to precisely characterize the role of a gene in vivo, mutations should be designed. The simplicity and utility of transgenic technology can satisfy this demand. The combination of RNA interference with transgenic technology will provide more opportunities for researchers. Nevertheless, gene targeting can solely define the in vivo function of a gene without a doubt. Thus, transgenesis and gene targeting will be the major strategies in the field of functional genomics.

• Journal of Microbiology and Biotechnology
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• v.18 no.8
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• pp.1401-1407
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• 2008

The roles of conserved amino acid residues (Va1329-Ala330-Asn331-Glu332), constituting an extra sugar-binding space (ESBS) of Thermus maltogenic amylase (ThMA), were investigated by combinatorial saturation mutagenesis. Various ThMA mutants were firstly screened on the basis of starch hydrolyzing activity and their enzymatic properties were characterized in detail. Most of the ThMA variants showed remarkable decreases in their hydrolyzing activity, but their specificity against various substrates could be altered by mutagenesis. Unexpectedly, mutant H-16 (Gly-Leu-Val-Tyr) showed almost identical hydrolyzing and transglycosylation activities to wild type, whereas K-33 (Ser-Gly-Asp-Glu) showed an extremely low transglycosylation activity. Interestingly, K-33 produced glucose, maltose, and acarviosine from acarbose, whereas ThMA hydrolyzed acarbose to only glucose and acarviosine-glucose. These results propose that the substrate specificity, hydrolysis pattern, and transglycosylation activity of ThMA can be modulated by combinatorial mutations near the ESBS.