• Korean Journal of Plant Tissue Culture
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• v.25 no.5
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• pp.341-346
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• 1998

In this paper we describe the cloning and expression of the genes encoding the flavonoid-biosynthetic enzyme dihydroflavonol 4-reductase (DFR) in Matthiola incana R. Br. A heterologous cDNA probe from Zea mays was used to isolate full-size DFR cDNA clone from a corolla-specific cDNA library. Comparison of the coding region of this DFR cDNA sequence including the sequences of Zea mays, Anthirrinum majus, Petunia hybrida, Callistephus chinensis, Dianthus caryophyllus and Rosa hybrida reveals a identity higher than 61% at the nucleotide level. The DFR transcript is G/C rich in monocotyledonous plants show a strong codon bias preferring codons with a G or C in the third position. The function of this nucleotide sequences were verified by comparison with amino acid sequences of the amino-terminus and tryptic peptides from purified plant enzyme, by northern blotting with mRNA from wild type and mutant plants and by in vitro expression yielding an enzymatically active reductase. Genomic southern blot analysis showed the presence of one gene for DFR in Matthiola incana. Northern blot analysis of the DFR wild type and mutant lines showed that the lack of DFR activity in the stable acyanic mutant k17b is clearly by a transcriptional block of the DFR gene.

• Journal of Microbiology and Biotechnology
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• v.17 no.12
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• pp.2046-2055
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• 2007

Wild-type V. vulnificus cannot grow using lactose as the sole carbon source or take up the sugar. However, prolonged culture of this species in media containing lactose as the sole carbon source leads to the generation of a spontaneous lactose-utilizing (LU) mutant. This mutant showed strong ${\beta}$-galactosidase activity, whereas the wild-type strain showed a barely detectable level of the activity. A mutant with a lesion in a gene homologous to the lacZ of E. coli in the bacterium no longer showed ${\beta}$-galactosidase activity or generated spontaneous LU mutants, suggesting that the lacZ homolog is responsible for the catabolism of lactose, but the expression of the gene and genes for transport of lactose is tightly regulated. Genetic analysis of spontaneous LU mutants showed that all the mutations occur in a lacI homolog, which is located downstream to the lacZ and putative ABC-type lac permease genes. Consistent with this, a genomic library clone containing the lad gene, when present in trans, made the spontaneous LU mutants no longer able to utilize lactose as the sole carbon source. Taken together with the observation that excessive amounts of exogenously supplemented possible catabolic products of lactose have negative effects on the growth and survivability of V. vulnificus, we suggest that V. vulnificus has evolved to carry a repressor that tightly regulates the expression of lacZ to keep the intracellular toxic catabolic intermediates at a sublethal level.

• Animal cells and systems
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• v.3 no.2
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• pp.229-236
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• 1999

The recA gene plays a central role in genetic recombination and SOS DNA repair in Escherichia coli (E. coli). We have previously identified a 42 kDa RecA-like protein inducible by a variety of DNA damages from a fluorescent Pseudomonas strain sp. and characterized its inducible kinetics. In the present study, we cloned and characterized the gene encoding the RecA-like protein by immunological screening of Pseudomonas genomic expression library using polyclonal E. coli anti-RecA antibodies as a probe. From 10$^{5}$ plaques screened, five putative clones were finally isolated. Southern blot analysis indicated that four clones had the same DNA inserts and the recA-like gene was located within the 3.2 kb EcoRI fragment of Pseudomonas chromosomal DNA. In addition, the cloned recA-like gene was transcribed into an RNA transcript approximately 1.1 kb in size, as judged by Northern blot analysis. The cellular level of RNA transcript of the cloned recA-like gene was increased to an average of 5.15- fold upon treatment with DNA damaging agents such as ultraviolet (UV)- light, nalidixic acid (NA), methyl methanesulfonate (MMS), and mitomycin-C (MMC). These results suggest that the cloned gene is inducible by DNA damage similarly to the recA gene in E. coli. However, the cloned gene did not restore the DNA damage sensitivity of the E. coli recA-mutant.

• Journal of Microbiology
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• v.45 no.6
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• pp.541-546
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• 2007

Red algae are distributed globally, and the group contains several commercially important species. Griffithsia okiensis is one of the most extensively studied red algal species. In this study, we conducted expressed sequence tag (ESTs) analysis and synonymous codon usage analysis using cultured G. okiensis samples. A total of 1,104 cDNA clones were sequenced using a cDNA library made from samples collected from Dolsan Island, on the southern coast of Korea. The clustering analysis of these sequences allowed for the identification of 1,048 unigene clusters consisting of 36 consensus and 1,012 singleton sequences. BLASTX searches generated 532 significant hits (E-value <$10^{-4}$) and via further Gene Ontology analysis, we constructed a functional classification of 434 unigenes. Our codon usage analysis showed that unigene clusters with more than three ESTs had higher GC contents (76.5%) at the third position of the codons than the singletons. Also, the majority of the optimal codons of G. okiensis and Chondrus crispus belonging to Bangiophycidae were G-ending, whereas those of Porphyra yezoensis belonging to Florideophycidae were G-ending. An orthologous gene search for the P. yezoensis EST database resulted in the identification of 39 unigenes commonly expressed in two rhodophytes, which have putative functions for structural proteins, protein degradation, signal transduction, stress response, and physiological processes. Although experiments have been conducted on a limited scale, this study provides a material basis for the development of microarrays useful for gene expression studies, as well as useful information for the comparative genomic analysis of red algae.

• Journal of Microbiology and Biotechnology
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• v.6 no.5
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• pp.331-335
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• 1996

The second $\beta$-Xylosidase gene (xylB) from Bacillus stearothermophilus was isolated from the genomic library, cloned into pBR322, and subsequently transferred into Escherichia coli HB101. Six out of 10, 000 transformants were selected from the selective LB medium supplemented with p-nitrophenyl-$\alpha$-L-arabinofuranoside (pNPAf) and ampicillin ($50\mu g$/ml) based on their ability to form a yellow ring around the colony. One of the clones was found to harbor the recombinant plasmid with 5.0 kb foreign DNA, which was identical to the $\alpha$-L-arabinofuranosidase gene (arfI) previously cloned in this lab, while the other five had 3.5 kb of the foreign DNA. Southern blotting experiments confirmed that the 3.5 kb insert DNA was from B. stearothermophilus chromosomal DNA. A zymogram with 4-methylumbelliferyl-$\alpha$-L-arabinofuranoside as the enzyme substrate revealed that the cloned gene product was one of the mutiple $\alpha$-L-arabinofuranosidases produced by B. stearothermophilus. Unlike the arfI gene product, the product of the gene on the insert DNA (xylB) showed an activity not only on pNPAf but also on oNPX suggesting that the cloned gene product could be a bifunctional enzyme having both $\alpha$-L-arabinofuranosidase and $\beta$-xylosidase activities.

• Journal of Microbiology and Biotechnology
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• v.18 no.3
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• pp.449-456
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• 2008

Phenotypic screening for bile salt hydrolase (BSH) activity was performed on Lactobacillus acidophilus PF01 isolated from piglet feces. A gene encoding BSH was identified and cloned from the genomic library of L. acidophilus PF01. The bsh gene and surrounding regions were characterized by nucleotide sequence analysis and were found to contain a single open reading frame (ORF) of 951 nucleotides encoding a 316 amino acid protein. The potential bsh promoter region was located upstream of the start codon. The protein deduced from the complete ORF had high similarity with other BSHs, and four amino acid motifs located around the active site, FGRNXD, AGLNF, VLTNXP, and GXGXGXXGXPGD, were highly conserved. The bsh gene was cloned into the pET21b expression vector and expressed in Escherichia coli BLR(DE3) by induction with 0.1mM of isopropylthiogalactopyranoside. The BSH enzyme was purified with apparent homogeneity using a $Ni^{2+}$-NTA agarose column and characterized. The overexpressed recombinant BSH enzyme of L. acidophilus PF01 exhibited hydrolase activity against tauroconjugated bile salts, but not glycoconjugated bile salts. It showed the highest activity against taurocholic acid. The maximum BSH activity occurred at approximately $40^{\circ}C$. The enzyme maintained approximately 70% of its maximum activity even at $60^{\circ}C$, whereas its activity rapidly decreased at below $37^{\circ}C$. The optimum pH was 6, and BSH activity was rapidly inactivated below pH 5 and above pH 7.

• Journal of Microbiology and Biotechnology
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• v.18 no.3
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• pp.410-416
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• 2008

The gene SfXyn10, which encodes a protease-resistant xylanase, was isolated using colony PCR screening from a genomic library of a feather-degrading bacterial strain Streptomyces fradiae var. k11. The full-length gene consists of 1,437bp and encodes 479 amino acids, which includes 41 residues of a putative signal peptide at its N terminus. The amino acid sequence shares the highest similarity (80%) to the endo-1,4-${\beta}$-xylanase from Streptomyces coelicolor A3, which belongs to the glycoside hydrolase family 10. The gene fragment encoding the mature xylanase was expressed in Escherichia coli BL21 (DE3). The recombinant protein was purified to homogeneity by acetone precipitation and anion-exchange chromatography, and subsequently characterized. The optimal pH and temperature for the purified recombinant enzyme were 7.8 and $60^{\circ}C$, respectively. The enzyme showed stability over a pH range of 4.0-10.0. The kinetic values on oat spelt xylan and birchwood xylan substrates were also determined. The enzyme activity was enhanced by $Fe^{2+}$ and strongly inhibited by $Hg^{2+}$ and SDS. The enzyme also showed resistance to neutral and alkaline proteases. Therefore, these characteristics suggest that SfXyn10 could be an important candidate for protease-resistant mechanistic research and has potential applications in the food industry, cotton scouring, and improving animal nutrition.

• Proceedings of the Korean Society of Developmental Biology Conference
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• 2003.10a
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• pp.121-121
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• 2003

The standard protocol for the production of transgenic mouse from ES-injected embryo has to process via chimera producing and several times breeding steps, In contrast, tetraploid-ES cell complementation method allows the immediate generation of targeted murine mutants from genetically modified ES cell clones. The advantage of this advanced technique is a simple and efficient without chimeric intermediates. Recently, this method has been significantly improved through the discovery that ES cells derived from hybrid strains support the development of viable ES mice more efficiently than inbred ES cells do. Therefore, the objective of this study was to generate transgenic mice overexpressing human resistin gene by using tetrapioid-ES cell complementation method. Human resistin gene was amplified from human fetal liver cDNA library by PCR and cloned into pCR 2.1 TOPO T-vector and constructed in pCMV-Tag4C vector. Human resistin mammalian expression plasmid was transfected into D3-GL ES cells by lipofectamine 2000, and then after 8~10 days of transfection, the human resistin-expressing cells were selected with G418. In order to produce tetraploid embryos, blastomeres of diploid embryos at the two-cell stage were fused with two times of electric pulse using 60 V 30 $\mu$sec. (fusion rate : 93.5%) and cultured upto the blastocyst stage (development rate : 94.6%). The 15~20 previously G418-selected ES cells were injected into tetraploid blastocysts, and then transferred into the uterus of E2.5d pseudopregnant recipient mice. To investigate the gestation progress, two El9.5d fetus were recovered by Casarean section and one fetus was confirmed to contain human resistin gene by genomic DNA-PCR. Therefore, this finding demonstrates that tetraploid-ES mouse technology can be considered as a useful tool to produce transgenic mouse for the rapid analysis of gene function in vivo.

• KSBB Journal
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• v.19 no.4
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• pp.308-314
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• 2004

A degenerate set of PCR primers based on two conserved regions (heme binding region and oxygen ligand pocket) were designed and successfully applied to amplify DNA fragments of cytochrome P450 hydroxylase (CYP) genes from a rare actinomycetes, S. benihana. The PCR amplified products were employed as a DNA probe to clone the entire CYP genes from S. benihana genomic library. Five different CYP-positive cosmids were isolated by colony hybridization as well as PCR confirmation. The complete nucleotide sequencing of five different CYP genes revealed that each unique CYP showed a significant amino acid homology to previously-known CYP genes involved in streptomycetes secondary metabolism. In addition, four CYP genes (CYP502, CYP503, CYP504, CYP506) were found to be linked to ferredoxin genes in the chromosome, and the CYP503 gene showed the high degree of amino acid similarity to the previously well-characterized CYP105 family in streptomycetes.

• Proceedings of the Microbiological Society of Korea Conference
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• 2001.11a
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• pp.16-25
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• 2001

A genomic library of biphenyl-degrading strain Comamonas sp. SMN4 was constructed by using the cosmid vector pWE15 and introduced into Escherichia coli. Of 1,000 recombinant clones tested, two clones that expressed 2,3-dihydroxybiphenyl 1,2-dioxygenase activity were found (named pNB 1 and pNB2). From pNB1 clone, subclone pNA210, demonstrated 2,3-dihydroxybiphenyl 1,2-dioxygenase activity, is isolated. 2,3-Dihydroxybiphenyl 1,2-dioxygenase (23DBDO, BphC) is an extradiol-type dioxygenase that involved in third step of biphenyl degradation pathway. The nucleotide sequence of the Comamonas sp. SMN4 gene bphC, which encodes 23DBDO, was cloned into a plasmid pQE30. The His-tagged 23DBDO produced by a recombinant Escherichia coli, SG 13009 (pREP4)(pNPC), and purified with a Ni-nitrilotriacetic acid resin affinity column using the His-bind Qiagen system. The His-tagged 23DBDO construction was active. SDS-PAGE analysis of the purified active 23DBDO gave a single band of 32 kDa; this is in agreement with the size of the bphC coding region. The 23DBDO exhibited maximum activity at pH 9.0. The CD data for the pHs, showed that this enzyme had a typical a-helical folding structures at neutral pHs ranged from pH 4.5 to pH 9.0. This structure maintained up to pH 10.5. However, this high stable folding strucure was converted to unfolded structure in acidic region (pH 2.5) or in high pH (pH 12.0). The result of CD spectra observed with pH effects on 23DBDO activity, suggested that charge transition by pH change have affected change of conformational structure for 23DBDO catalytic reaction. The $K_m$ for 2,3-dihydroxybiphenyl, 3-metylcatechol, 4-methylcatechol and catechol was 11.7 $\mu$M, 24 $\mu$M, 50 mM and 625 $\mu$M.