• Title/Summary/Keyword: Mutant

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In Vivo Analysis of fadB Homologous Enzymes Involved in Biosynthesis of Polyhydroxyalkanoates in Recombinant Escherichia coli (재조합 대장균에서 fadB 유사효소의 Polyhydroxyalkanoates 합성에 미치는 역할의 규명)

  • 최종일;박시재;이상엽
    • KSBB Journal
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    • v.19 no.4
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    • pp.331-334
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    • 2004
  • In vivo characterization of FadB homologous enzymes including PaaG, YdbU and YgfG for medium-chain-length (MCL) polyhydroxyalkanoate (PHA) biosynthesis was carried out in fadB mutant Escherichia coli. Previously, it was reported that amplification of FadB homologous enzymes such as PaaG and YdbU in fadB mutant E. coli resulted in enhanced biosynthesis of MCL-PHA by greater than two fold compared with control strain. In this study, we constructed paaG fadB double mutant E. coli WB114 and ydbU fadB double mutant E. coli WB115 to investigate the roles of PaaG and YdbU in biosynthesis of MCL-PHA. Inactivation of paaG and ydbU genes in fadB mutant E. coli harboring Pseudomonas sp. 61-3 phaC2 gene reduced the MCL-PHA production to 0.16 and 0.16 PHA g/L, respectively from 2 g/L of sodium decanoate, which are much lower than 0.43 PHA g/L obtained with fadB mutant E. coli WB101 harboring the phaC2 gene. Also, we identified new FadB homologous enzyme YgfG, and examined its roles by overexpression of ygfG and construction of ygfG fadB double mutant E. coli WB113.

Further induction of amylase producing mutants from a highly proteolytic mutant strain of asppergillus flavus (돌연변이에 의한 Aspergillus flavus의 아밀라아제 생성능의 개량)

  • 이영록;고상균;김봉수
    • Korean Journal of Microbiology
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    • v.18 no.4
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    • pp.161-171
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    • 1980
  • A mutant strain having increased productivity of both enzymes, protease and amylase, was obtained from A. flavus KU 153, isolatd from South Korea for its high protease production by successive ultra-violet light irradiation, Two glucoamylases from the mutant strain selected were purified from wheat branculture by successive salting out, followed by dialysis and column chromatography, and their characteristics were compared with those of the wild strain. Glucoamylase production of the mutant selected was increased about 3.3 times compared with the wild strain, and 2.1 times compared with the parental strain, ${\alpha}-amylase$ activity of the mutant selected was about 2 times hugher than that of the wild strain or the parental strain. Protease and cellulase productivities of the muant selected were all alike compared with those of the highly proteolytic mutant, the parental strain. Therefore, it was considered that the back mutation on the protease production did not occurred in the formation process of the glucoamylase producing mutant. Total activities of glucoamylase I and II from the mutant selected were 2.86 and 3.65 times higher compared with those from the wild strain, respectively. Considering the optimal pH-thermal stability and Km-Vmax value of glucoamylase I and II from both strains, wild and mutant, it was deduced that the characteristics of glucoamylase I and II from the wild strain did not altered during the mutation process. Therefore, it was concluded that the selected mutant did not induce the formation of another glucoamylase isozyme, or the changes in the characteristics of the glucoamylase, but induce the productivity of the same glucoamylase I and II by the action of regulatory gene.

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Degeneration of Ocellar Photoreceptor System on Drosophila rdgC Mutant (초파리 rdgC 돌연변이체 단안 시각계의 퇴행현상)

  • Yoon, Chun-Sik
    • Applied Microscopy
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    • v.28 no.3
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    • pp.391-398
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    • 1998
  • The morphological phenotype on ocellus of Drosophila rdgC mutant was observed with electron microscope. The result showed the particular phenotype that was not found in other retinal degenarative mutants. The most distinct difference was the orientation of photoreceptor cells. The photoreceptor cells did not attached to corneagenous cells but dropped under corneagenous cells and assembled around newly formed space. Enormous multivesicle bodies caused by the degeneration of photoreceptor cells were frequently found. Rhabdomeres were also severely degenerated in consequence of the mutant. Another degeneration was found in a part of photoreceptor cell, but the degeneration of subrhabdomeric cisternae (SRC) was not found. It was a ovious difference of rdgC comparing with other two retinal degenerative mutants, rdgA and rdgB. As a result, rdgC mutant was affected on the attachment between photoreceptor cells and corneageneous cells, and it suggested the defect of cell-cell attachment. In addition, rdgC mutant was accompanied by the defect not only in retina but nerve system. The results were agreed to the reference discussion that the rdgC molecule is exist in the nerve.

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On a highly proteolytic mutant strain of Aspergillus flavus (Aspergillus flavus의 강력 protease생성 돌연변이의 유발)

  • 이영녹;박용근;고상균
    • Korean Journal of Microbiology
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    • v.18 no.2
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    • pp.51-58
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    • 1980
  • Mutational experiments were performed to improved to improve the protease productivity of Aspergillus flavus KU 153, which is selected among the wild strains. A UV-induced mutant strain having high protease productivity was obtained by the use of the clear zone method as a simple criterion for a primary screening test. Neutral and alkaline protease activities of hte mutant strain were higher than 1.8 times, comopared with those of the parental strain, respectively, while in the case of acid protease, it was 2.7 times. The mutant strain selected was more powerful in the production of cellulase and amylase, as well s protease in wheat bran, compared with those of the parental strain. protease production of the parental strain has reached maximum level at 3 days culture, while alkaline nad neutral protease production of the mutantstrain has reached at 2 days culture. On the other hand, the mutant strain formed the spore slowly, compared with the parental strain. Column chromatography of the neutral protease on DEAE-Sephadex A-50 showed that the mutant strain was not induced the formation of another neutral protease isozyme, but induced the variation in the function of regulatory gene.

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Simultaneous enhancement of thermostability and catalytic activity of phospholipase $A_1$ by evolutionary molecular engineering

  • Song, Jae-Kwang;Rhee, Joon-Shick
    • Proceedings of the Korean Society for Applied Microbiology Conference
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    • 2000.04a
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    • pp.168-171
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    • 2000
  • The thermal stability and catalytic activity of phospholipase A$_1$ from Serratia sp. MK1 were improved by an evolutionary molecular engineering. Two thermostable mutants were isolated after sequential rounds of error-prone PCR to introduce random mutations and filter-based screening of the resultant mutant library, and identified as having six (mutant TA3) and seven (mutant TA13) amino acid substitutions, respectively. Different types of the substitutions were found in two mutants, resulting in the increase of nonploar residues (mutant TA3) or changes between side chains within polar or charged residues (mutant TA13). The wild-type and mutant enzymes were purified, and the effect of temperature on their stability and catalytic activity was investigated. The T$\sub$m/ values of TA3 and TA13 were increased by 7 and 11$^{\circ}C$, respectively. Thus, evolutionary molecular engineering was found to be an effective and efficient approach to increasing thermostability without compromising enzyme activity.

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Ingibition of coliphage N4 infection to escherichia coli mutant defective in mannose permease (Mannose permease가 변형된 대장균 변이주에 대한 coliphage N4 감염의 저해)

  • 김기태;유욱준
    • Korean Journal of Microbiology
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    • v.25 no.3
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    • pp.184-188
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    • 1987
  • Evidences that the mannose permease of Escherichia coli mediates the infection of N4 in early steps, were obtained as follows. First, A mutant strain of Escherichia coli which was resistant to both wild type N4 and lambda whose genome is Charon 4A containing human genomic fragments in its EcoR I site, could not use mannose efficiently. Second, N4 could not infect pel mutant strains which lack one or all of intact components of mannose permease. However, unknown alterations in N4 made it possible for the phage to infect pel mutant of E. coli. It also turned out to be clear that the receptor of N4 was different from that of lambda.

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Influence of Site-Directed Mutagenesis on Protein Assembly and Solubility of Tadpole H-chain Ferritin

  • Kim, Kyung-Suk
    • Biotechnology and Bioprocess Engineering:BBE
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    • v.3 no.2
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    • pp.67-70
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    • 1998
  • In order to understand the influence of ferroxidase center on the protein assembly and solubility of tadpole ferrin, three mutant plasmids, pTH58K, pTH61G, and pTHKG were constructed with the aid of site-directed mutagenesis and mutant proteins were produced in Eshcerichia coli. Mutant ferritin H-subunits produced by the cells carrying plasmids pTH58K and pTHKG were active soluble proteins, whereas the mutant obtained from the plasmid pTH61G was soluble only under osmotic stress in the presence obtained from the plasmid pTH61G was soluble only under osmotic stress in the presence of sorbitol and betaine. Especially, the cells carrying pTH61G together with the plasmid pGroESL harboring the molecular chaperone genes produced soluble ferritin. The mutant ferritin H-subunits were all assembled into ferritin-like holoproteins. These mutant ferritns were capable of forming stable iron cores, which means the mutants are able to accumulate iron with such modified ferroxidase sites. Further functional analysis was also made on the individual amino acid residues of ferroxidase center.

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Studies on the lactose constitutive mutants of Streptococcus lactis $KB_{21}$ (Streptococcus lactis $KB_{21}$의 lactose constitutive mutant에 관한 연구)

  • Park, Yun-Hee;Mckay, Larry L.
    • Applied Biological Chemistry
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    • v.23 no.4
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    • pp.218-221
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    • 1980
  • From S. lactis $KB_{21}$, stabilized strain by intergration of the lactose plasmid into the host chromosome, several lactose constitutive mutants were obtained by UV irradiation and spontaneous mutation. The rapid growth of the mutants in the medium containing lactobionate confirmed their constitutive nature. The mutants synthesized $phospho-{\beta}-galactosidase$ with an activity of 1.7 to 3.4 times that of the parent.

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Induction and Selection of Citrus Mutant by Gamma-Irradiation (감마선조사를 통한 돌연변이 궁천조생 감귤 가지 유도 및 선발)

  • Kim, In-Jung;Oh, Seung Kyu;Lee, Hyo Yeon
    • Journal of Radiation Industry
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    • v.4 no.3
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    • pp.215-219
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    • 2010
  • We have subjected to gamma-irradiation to citrus buds and then grafted onto mature citrus tree. Mutant citrus branch lines have been induced. As a result of first selection, we found the several mutant lines showing interesting phenotypes such as higher sugar content. We have selected several branches showing good qualities such as higher sweetness and/or lower acidity. Some branch lines showed over $13^{\circ}Brix$ sugar content and below 0.9% acidity. Other mutant branch lines showed the changes of shape, size, peel thickness, and fiber contents or distribution of fruits. The results suggest that gamma-irradiation is an effective tool for induction of citrus mutant lines.

Characteristics and Genetic Segregation of a Rolled Leaf Mutant in Rice

  • Lee, Songyee;Choi, Minseon;Lee, Joohyun;Koh, Hee-Jong
    • Korean Journal of Breeding Science
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    • v.43 no.4
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    • pp.260-264
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    • 2011
  • Leaf structure is one of the important agronomic traits. A rolled leaf mutant was induced from an ethyl methane sulfonate (EMS)-treated japonica rice, 'Koshihikari'. The rolled leaf mutant showed phenotypes of reduced leaf width and leaf rolling. In addition, several abnormal morphological characteristics were observed, including dwarfism, defected panicle, delayed germination, and lower seed-setting. Microscopic analysis revealed that the number of small veins was decreased and the sizes of adaxial bulliform cells were reduced in the mutant leaves. The genetic study with two $F_2$ populations from the crosses of the rolled leaf mutant with 'Koshihikari' and Milyang23 suggested that the mutant phenotype might be controlled by a single dominant gene.