• Applied Biological Chemistry
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• v.40 no.3
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• pp.189-195
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• 1997

The structural basis of Iysine specificity of Achromobacter protease I (API) was investigated by means of site-directed mutagenesis. The precursor protein in which Glu190, one of the two candidates for determining Iysine specificity, was substituted by glutamine, aspartic acid or leucine was processed autocatalytically to attaln full pretense activity with lysine specificity. The substitution of the other candidate, Asp225, for asparagine or leucine produced no mature active forms of pro-API. The precursor protein of the mutant D225E slowly matured autocatalytically. The lysylendopeptidase activity of the mature D225E was 0.25% of that of native API, and this reduced activity is mainly due to a decrease in the affinity of the enzyme for lysine. These results suggest that Asp225 plays a critical rol in restricted substrate specificity as a lysylendopeptidase. However, D225E exhibited no measurable activity for synthetic ornithine substrate. Since the hydroxyl group of Ser194 in this mutant retained essentially the same reactivity to DFP or PMSF as that in native API, it can be noted that a methylene unit longer side chain of residue 225 is not compensated by a methylene unit shorter side chain at subsite P1 in the bound substrate.

• Korean Journal of Microbiology
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• v.27 no.3
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• pp.176-180
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• 1989

There are three pseudourdine ($Psi$)bases in the E. coli $tRNA^{phe}$ In order to study the function of the pseudouridine bases in the $tRNA^{phe}$, changes of bases $tRNA^{phe}$ gene to other bases were undertaken by the site-specific mutagenesis. Site-specific mutagenesis of T in the pheW gene, a $tRNA^{phe}$ gene of E. coli, corresponding to the baseat the No.32 position to C and also T corresponding to the base at the No.39 position to C were performed using Kunkel's uracil-containing template method. Identification of mutants were undertaken by the KNA sequencing techniques of the mutated pheW genes and activities of the mutated pheW genes complementing to E. coli NP37 mutant($pheS^{-ts}$) using the recombinant plasmid containing the mutated genes. Neither NP37 harboring pheW gene mutated at No.32 position nor NP37 harboring pheW gene mutated at No.39 position can be grown at non-permissive temperature. The result means that both mutated pheW genes can not complement to E. coli NP37, and that the pseudouridine bases are essential to the activity of the E. coli $tRNA^{phe}$ in vivo.

• Korean Journal of Veterinary Research
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• v.37 no.3
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• pp.541-546
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• 1997

There are two conserved regions with a significantly high amino acid sequence homology among the A subunits of STX, SLTs and ricin. To produce an inactive Verotoxin-2 (VT-2), two different mutants, pE167D and pDE5A, were constructed by site-directed mutagenesis, respectively, on the basis of the previous reports that two regions lie within the active-site clefts of the A subunits of ricin and STX family. The cytotoxicity ($10^3$ $CD_{50}/ml$) of VT-2 holotoxin with E167D mutation was reduced by $10^3$-fold compared with wild-type level. In addition, VT-2 with DE5A ($Trp_{202}GlyArgIleSer_{206}$) deletion mutation showed a significantly low cytotoxicity ($10^1$ $CD_{50}/ml$), resulting in $10^5$- and $10^2$-fold reductions, respectively, compared with the wild-type and E167D mutatant. SDS-PAGE for protein samples showed a 33-kDa band corresponding to the A subunit of VT-2. These results indicate that reduction in cytotoxic activity was affected not by amount of VT-2 protein produced but by mutation.

• Journal of Life Science
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• v.20 no.9
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• pp.1332-1338
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• 2010

To elucidate the mechanism underlying the regulation of hST8Sia I gene expression in FenR-induced SH-SY5Y cells, we characterized the promoter region of the hST8Sia I gene. Functional analysis of the 5'-flanking region of the hST8Sia I gene showed that the -1146 to -646 region functions as the FenR-inducible promoter of hST8Sia I in SH-SY5Y cells. Site-directed mutagenesis indicated that the NF-&B binding site at -731 to -722 was crucial for the FenR-induced expression of hST8Sia I in SH-SY5Y cells. To investigate which signal transduction pathway was involved in FenR-stimulated induction of hST8Sia I in SH-SY5Y cells, we performed Western blot analysis using phospho-specific antibodies in order to measure their degree of regulatory phosphorylation. Phosphorylations of AKT and RelA (p65) subunit of NF-${\kappa}B$ were significantly elevated in cytosolic and nuclear fractions of FenR-stimulated SH-SY5Y cells, respectively, than in control or DMSO-treated SH-SY5Y cells. These results suggest that FenR induce transcriptional up-regulation of hST8Sia I gene expression through translocation of RelA (p65) subunit of NF-${\kappa}B$ to nucleus by AKT signal pathway in SH-SY5Y cells.

• Journal of Life Science
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• v.20 no.5
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• pp.655-661
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• 2010

To elucidate the mechanism underlying the suppressive regulation of hST8Sia I expression in retinoic acid (RA)-induced SK-MEL-2 cells, we characterized the promoter region of the hST8Sia I gene. Functional analysis of the 5‘-flanking region of the hST8Sia I gene by the transient expression method showed that the -1146 to -646 region, which contains putative binding sites for transcription factors c-Ets-1, CREB, AP-1 and NF-kB, functions as the RA-repressive promoter in SK-MEL-2 cells. Site-directed mutagenesis and ChIP analyses indicated that the NF-kB binding site at -731 to -722 is crucial for the RA-induced repression of hST8Sia I in SK-MEL-2 cells. In addition, the transcriptional activity of hST8Sia I suppressed by RA in SK-MEL-2 cells was strongly inhibited by extracellular signal-regulated protein kinase (ERK) inhibitor U0126 and protein kinase C (PKC) inhibitor GO6976, as determined by RT-PCR and luciferase assay of hST8Sia I promoter containing the -1146 to -646 regions. These results suggest that RA markedly modulates transcriptional regulation of hST8Sia I gene expression through the PKC/ERK signal pathway in SK-MEL-2 cells.

• Journal of Animal Science and Technology
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• v.48 no.1
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• pp.1-8
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• 2006

KIT encodes a mast/stem cell growth factor receptor and is known as a possible candidate gene responsible for dominant white coat color in mammals. To investigate the genetic variation of KIT gene in Korean wild boars(Sus scrofa coreanus), we carried out PCR-RFLP and DNA sequencing for three exons(exons 17, 19, and 20) and intron 19 of the KIT gene in Korean wild boars. PCR-RFLP results using NlaⅢ restriction enzyme in the breakpoint region between exon 17 and intron 17 and AciⅠ restriction enzyme in exon 19 indicate that Korean wild boars did not have previously identified white coat color related splicing mutation and missense mutation, respectively. These results also indicate matings between Korean wild boars could not give white coat color offsprings. We also found new SNPs in exons 19(C2661T) and 20(A2760G). Of these, the SNP in exon 20 is a missense mutation which might induce the change of amino acid iso-leucine to valine. However, no relationship was identified with this missense mutation and coat color. In this study, breed specific new SNPs were identified in exons 19, 20 and intron 19 and these results will give important information for genetic variation of porcine KIT gene.