• Journal of Radiation Protection and Research
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• v.22 no.1
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• pp.15-21
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• 1997

In vitro somatic mutation induced by ${\gamma}$-radiation and pentachlorophenol(PCP) which is representative of chemical pollutant was measured at the hypoxanthine-guanine phosphoribosyl transferase(hprt) locus in human T- lymphocytes by a cell cloning assay. Mutant cells were selected by their ability to form a clone in the presence of purine analogue 6-thioguanine. The mutant frequencies by ${\gamma}$-irradiation to a dose of 1.0 Gy, 2.0 Gy and 3.0 Gy were 40%, 400% and 750% higher than those in controls. Significant changes were not observed in mutant frequencies in the 0.2 Gy and 0.5 Gy irradiated groups. When the doses of PCP were 15 ppm, 25 ppm and 50 ppm, the mutant frequencies increased by 30%, 90% and 520%, respectively. No changes were observed in the 10 ppm treated group. Similar types of dose-response relationship were shown in the two different mutagens. Reverse transcriptase/polymerase chain reaction technique(RT/PCR) was needed for the mutation spectrum to discriminate combined exposure to radiation and chemicals.

• Korean Journal of Microbiology
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• v.45 no.3
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• pp.268-274
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• 2009

A photosynthetic cyanobacterium Arthrospira platensis, well known for health food supplement, was studied as a target species for atmospheric $CO_2$ removal as well as biomass production. Although the biomass of A. platensis was massively produced in many countries, the recovery cost of its biomass is still high. The purpose of this study was to develop the A. platensis mutant strains which have enhanced growth rate and floatation activity to reduce the recovery cost. A. platensis KCTC AG20590 was treated with 0.24% ethyl methanesulfonate (EMS) for 20 min at room temperature. The mutant strain A. platensis M20CJK3 was finally selected by its morphological and physiological features. The morphology of the mutant A. platensis M20CJK3 was changed from loose-coiled form to tight-coiled form showing short pitch. The growth and $CO_2$ uptake rate of A. platensis M20CJK3 were improved about 15% and 17% compared with A. platensis KCTC AG20590, respectively. The floatation activity of A. platensis M20CJK3 was enhanced in 2-fold compared with that of A. platensis KCTC AG20590. Soluble proteins extracted from two strains were analyzed by two dimensional electrophoresis (2-DE) and MALDI-TOF MS/MS. Among 15 protein spots induced in 2-DE analysis, two spots were the proteins related to photosynthesis and electron transfer system of the other cyanobacteria. As a consequence, it seems that the tight-coiled mutant A. platensis M20CJK3 has an advantage of high growth rate and floatation activity which are beneficial for the mass cultivation and recovery.

• Journal of Life Science
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• v.22 no.7
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• pp.863-870
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• 2012

Rhodopsin, a dim light photoreceptor, has been regarded as one of the model systems for the structural and functional study of G protein-coupled receptors (GPCRs). Constitutively active mutant GPCRs leading to the activation of heterotrimeric GDP/GTP-binding protein signaling in the absence of ligand binding are of interest for the study of the activation mechanism in GPCRs. The present study focused on the opsin mutant E134Q/M257Y, which showed a moderate level of constitutive activity and the formation of two distinct rhodopsin chromophores with absorption maxima of 500 nm and 380 nm, depending on the presence of an inverse agonist, 11-cis-retinal, and an agonist, all-trans-retinal, respectively. Reconstitution of the mutant rhodopsin upon incubation with different ratios of 11-cis-retinal and the all-trans-retinal, as well as upon sequential binding of the two retinals, indicated its preferential binding to 11-cis-retinal. The thermal stability of the 11-cis-retinal-bound form of the E134Q/M257Y mutant was lower than that of the mutants containing a single replacement but higher than that of the all-trans-retinal-bound forms. The mutant also showed a lower stability in its opsin state as compared with that of the wild-type opsin but had little effects on the binding affinity to 11-cis-retinal. Information obtained in this study will be helpful for analyzing the structural changes associated with the activation of rhodopsin and GPCRs.

• International Journal of Industrial Entomology and Biomaterials
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• v.19 no.1
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• pp.199-204
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• 2009

The newly cloned Bacillus thuringiensis cry1-5 gene showed high activity to both Plutella xylostella and Spodoptera exigua, while cry1Ac only showed high activity against P. xylostella but low to S. exigua. Through the alignment of amino acid sequences between Cry1Ac and Cry1-5, we found 12 different residues in domain I (6 residues) and domain II (6 residues). In this study, the modified cry1Ac gene, which is constructed according to a crop-preferring codon usage, was used as a template to construct mutant B. thuringiensis cry1Ac genes based on cry1-5 gene through multi site-directed mutagenesis. Total 63 various mutant cry genes were obtained at 12 positions randomly. Among them, ten mutant cry genes, whose domain I was totally converted and domain II was randomly, were selected to express in baculovirus expression system as a polyhedrin fusion form. The recombinant proteins were 95 kDa in size and were stably activated as 65 kDa by trypsin. The expressed mutant Cry proteins were applied to bioassays against P. xylostella and S. exigua. All mutants showed high insecticidal activity both to P. xylostella and S. exigua similar to cry1-5. These results suggest that these mutant cry genes might be expected of desirable cry genes for introduction to transgenic crops.

• Journal of Applied Biological Chemistry
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• v.60 no.3
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• pp.249-256
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• 2017

The Monascus azaphilone (MAz) pigment is a well-known food colorant that has yellow, orange and red components. The structures of the yellow and orange MAz differ by two hydride reductions, with yellow MAz being the reduced form. Orange MAz can be non-enzymatically converted to red MAz in the presence of amine derivatives. It was previously demonstrated that mppE and mppG are involved in the biosynthesis of yellow and orange MAz, respectively. However, ${\Delta}mppE$ and ${\Delta}mppG$ knockout mutants maintained residual production of yellow and orange MAz, respectively. In this study, we deleted the region encompassing mppD, mppE and mppG in M. purpureus and compared the phenotype of the resulting mutant (${\Delta}mppDEG$) with that of an mppD knockout mutant (${\Delta}mppD$). It was previously reported that the ${\Delta}mppD$ strain retained the ability to produce MAz but at approximately 10% of the level observed in the wildtype strain. A chemical analysis demonstrated that the ${\Delta}mppDEG$ strain was still capable of producing both yellow and orange MAz, suggesting the presence of minor MAz route(s) not involving mppE or mppG. Unexpectedly, the ${\Delta}mppDEG$ strain was observed to accumulate fast-eluting pigments in a reverse phase high-performance liquid chromatography analysis. A LC-MS analysis identified these pigments as ethanolamine derivatives of red MAz, which had been previously identified in an mppE knockout mutant that produces high amounts of orange MAz. Although the underlying mechanism is largely unknown, this study has yielded an M. purpureus strain that selectively accumulates red MAz.

• Korean Journal of Environmental Agriculture
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• v.25 no.2
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• pp.124-128
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• 2006

To reducing offensive odor form compost UIW-6 mutant obtained by UV treatment from sulfur-oxidizing bacteria, Thiobacillus sp. IW. The UIW-6 mutant was found 1.6 times faster in growth than the parent strain on thiosulfate medium (TM) at 36 h after incubation. Initial pH, temperature and agitation for the optimum growth of UIW-6 were 6.5, $35^{\circ}C$ and 200 rpm, respectively. The UIW-6 mutant growth was two times higher than parent strain at 6 h culture in TM liquid medium containing 50 mM sodium thiosulfate. The UIW-6 mutant used fructose and sucrose as carbon sources and yeast extract> tryptone> peptone as nitrogen ones. It was found that the growth of UIW-6 was increased in addition of 0.2% yeast extract.

• BMB Reports
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• v.46 no.12
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• pp.617-622
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• 2013

Rac1 plays a key role in neurite outgrowth via reorganization of the actin cytoskeleton. The molecular mechanisms underlying Rac1-mediated actin dynamics in the cytosol and plasma membrane have been intensively studied, but the nuclear function of Rac1 in neurite outgrowth has not yet been addressed. Using subcellular fractionation and immunocytochemistry, we sought to explore the role of nuclear Rac1 in neurite outgrowth. bFGF, a strong agonist for neurite outgrowth in PC12 cells, stimulated the nuclear accumulation of an active form of Rac1. Rac1-PBR (Q) mutant, in which six basic residues in the polybasic region at the C-terminus were replaced by glutamine, didn't accumulate in the nucleus. In comparison with control cells, cells expressing this mutant form of Rac1 displayed a marked defect in extending neurites that was concomitant with reduced expression of MAP2 and MEK-1. These results suggest that Rac1 translocation to the nucleus functionally correlates with bFGF-induced neurite outgrowth.

• IMMUNE NETWORK
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• v.13 no.1
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• pp.16-24
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• 2013

CTLA-4Ig is regarded as an inhibitory agent of the T cell proliferation via blocking the costimulatory signal which is essential for full T cell activation. To improve applicability, we developed the CTLA-4Ig-CTKC in which the c-terminal lysine had been replaced by cysteine through single amino acid change. The single amino acid mutation of c-terminus of CTLA-4Ig was performed by PCR and was checked by in vitro transcription and translation. DNA construct of mutant form was transfected to Chinese hamster ovary (CHO) cells by electroporation. The purified proteins were confirmed by Western blot and B7-1 binding assay for their binding ability. The suppressive capacity of CTLA-4Ig-CTKC was evaluated by the mixed lymphocyte reaction (MLR) and in the allogeneic pancreatic islet transplantation model. CTLA-4Ig-CTKC maintained binding ability to B7-1 molecule and effectively inhibits T cell proliferation in MLR. In the murine allogeneic pancreatic islet transplantation, short-term treatment of CTLA-4Ig-CTKC prolonged the graft survival over 100 days. CTLA-4Ig-CTKC effectively inhibits immune response both in MLR and in allogeneic islet transplantation model, indicating that single amino acid mutation does not affect the inhibitory function of CTLA-4Ig. CTLA-4Ig-CTKC can be used in vehicle-mediated drug delivery system such as liposome conjugation.

• Journal of Microbiology and Biotechnology
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• v.12 no.2
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• pp.242-248
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• 2002

Previously, it was reported that the nonhomologous C-terminal regions of the D-hydantoinases are nonessential for catalysis, but affect the oligomeric structure of the enzyme [3]. In an effort to further confirm the above observation, the C-terminal region-inserted enzyme was constructed by attaching a peptide (22 residues) at the C-terminal of the D-hydantoinase from Bacillus thermocatenulatus GH2, and its structural and biochemical properties were compared with both the wild-type and C-terminal region-truncated enzymes. As a result, native tetrameric D-hydantoinase was dimerized as the truncated enzyme, and the inserted mutant with a new sequence was expressed as a catalytically active form in E. coli. Expression level of the inserted and truncated enzymes were found to be significantly increased compared to the level of the wild-type enzyme, and this appears to be due to the reduced toxic effect of the mutant enzymes on host cells. Dimerized enzymes exhibited increased thermo- and pH stabilities considerably when compared with the corresponding wild-type enzyme. Comparison of the substrate specificity between the mutant and wild-type enzymes suggests that the substrate specificity of the D-hydantoinase is closely linked with the oligomeric structure.

• Journal of Sericultural and Entomological Science
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• v.35 no.2
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• pp.93-99
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• 1993

Studies were carried out to investigate physiological and biochemical analysis of recessive lethal mutant "nmn" and to observe the cuticle formation and dermal gland. All nmn homozygous larvae continued to eat a few mulberry leaves, and died without entering into molt. In case of artificial hatching, eggs had a higher nmn individual segregation ratio than in hibernating eggs. The percentage of nmn individuals with the hatching days was alike during 3days period. As a result of histological observation, nmn mutants dermal gland was different from normal dermal gland in form and size. Normal was formed new cuticle in the middle of the molting, but not in nmn mutant. Total protein content in haemolymph of the normal larva was more than that of nmn smutant and there was a difference between normal and nmn mutant protein components.omponents.