• Title/Summary/Keyword: Methyltransferase

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Generation and characterization of calmodulin-DHFR sandwich fusion protein

  • Han, Chang Hoon
    • Korean Journal of Veterinary Research
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    • v.48 no.3
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    • pp.243-250
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    • 2008
  • A calmodulin-dihydrofolate reductase (DHFR) sandwich fusion protein was generated by insertion of calmodulin into the $\beta$-bulge region of DHFR to observe the effects of structurally constraining the calmodulin structure. The calcium binding properties of the sandwich protein were almost identical to calmodulin. Similar to calmodulin ($10.7 {\mu}M$), the sandwich protein bound four equivalents of calcium, with half saturation ($K_{0.5}$) observed at a [$Ca^{2+}$] of $8{\mu}M$. However, nicotinamide adenine dinucleotide (NAD) kinase activation property of the sandwich protein was lower than that of calmodulin. The sandwich protein activated NAD kinase, but to only half of the level obtained with calmodulin. The K 0.5 for both calmodulin and the sandwich protein were approximately the same (1-2 nM). Methylation analyses of the sandwich protein show that insertion of calmodulin into DHFR results in a large decrease in methylation. The $V_{max}$ observed with the sandwich protein (95 nmole/min/ml) was only 22% of the value observed with calmodulin (436 nmol/min/ml) in the presence of calcium. Addition of trimethoprim to the reaction significantly inhibited the observed methylation rate. Overall, the data suggest that the insertion of calmodulin into the DHFR structure has little effect on calcium binding by the individual lobes of calmodulin, but may constrain the lobes in a manner that results in altered interaction with the calmodulin-dependent proteins, and severely perturbed the methyltransferase recognition site.

Receptor-oriented Pharmacophore-based in silico Screening of Human Catechol O-Methyltransferase for the Design of Antiparkinsonian Drug

  • Lee, Jee-Young;Baek, Sun-Hee;Kim, Yang-Mee
    • Bulletin of the Korean Chemical Society
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    • v.28 no.3
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    • pp.379-385
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    • 2007
  • Receptor-oriented pharmacophore-based in silico screening is a powerful tool for rapidly screening large number of compounds for interactions with a given protein. Inhibition of the enzyme catechol-Omethyltransferase (COMT) offers a novel possibility for treating Parkinson's disease. Bisubstrate inhibitors of COMT containing the adenine of S-adenosylmethionine (SAM) and a catechol moiety are a new class of potent and selective inhibitor. In the present study, we used receptor-oriented pharmacophore-based in silico screening to examine the interactions between the active site of human COMT and bisubstrate inhibitors. We generated 20 pharmacophore maps, of which 4 maps reproduced the docking model of hCOMT and a bisubstrate inhibitor. Only one of these four, pharmacophore map I, effectively described the common features of a series of bisubstrate inhibitors. Pharmacophore map I consisted of one hydrogen bond acceptor (to Mg2+), three hydrogen bond donors (to Glu199, Glu90, and Gln120), and one hydrophobic feature (an active site region surrounded by several aromatic and hydrophobic residues). This map represented the most essential pharmacophore for explaining interactions between hCOMT and a bisubstrate inhibitor. These results revealed a pharmacophore that should help in the development of new drugs for treating Parkinson's disease.

Characterization of phenolic compounds biosynthesized in pink-colored skin of Japanese indigenous Vitis vinifera cv. Koshu grape

  • Kobayashi, Hironori;Suzuki, Yumiko;Ajimura, Kosei;Konno, Tomonori;Suzuki, Shunji;Saito, Hiroshi
    • Plant Biotechnology Reports
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    • v.5 no.1
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    • pp.79-88
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    • 2011
  • Vitis vinifera cv. Koshu is a traditional grape cultivar that has been grown for centuries in Japan. The Koshu grape has pink-colored skin and Koshu wines have slight astringency. We demonstrated for the first time the characterization of hydroxycinnamic acids, flavan-3-ols, and flavonoids in Koshu grape using high-performance liquid chromatography and liquid chromatography-mass spectrometry. The gross weight of phenolic compounds excluding anthocyanins and proanthocyanidins in Koshu grape at harvest was higher than those in Sauvignon Blanc, Chardonnay, and Merlot grapes. In addition, hydroxycinnamic acid and monomeric flavonol contents in Koshu grape were also higher than those in the other grape cultivars. Transcription analysis of cinnamic acid 4-hydroxylase, p-coumarate 3-hydroxylase, caffeate methyltransferase, and flavonol synthase genes indicated high accumulation of hydroxycinnamic acids and flavonols in Koshu grape skin compared with the other cultivars. These findings obtained by chemical and molecular approaches partially explained the phenolic characteristics and the peculiar astringency of Koshu grape.

An Association Study of COMT Gene Polymorphism with Korean Schizophrenics (정신분열병과 Catechol-O-methyltransferase(COMT) 유전자 다형성의 연합)

  • Song, En-Sook;Yang, Byung-Hwan;Park, Kang-Kyu;Lee, Yu-Sang;An, Eun-Soog;Oh, Dong-Yul;Kim, Jong-Won;Choi, Ihn-Geun;Kim, Gil-Sook;Chai, Young-Gyu
    • Korean Journal of Biological Psychiatry
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    • v.5 no.2
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    • pp.210-214
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    • 1998
  • An association study with Korean schizophrenic patients(N=84) and normal controls(N=87) was performed to find the relationship between catechol-O-methyltransferase(COMT) gene polymorphism and schizophrenia using polymerase chain reaction-restriction fragment length polymorphism. When we compared the allele and genotype frequencies of Bgl I COMT gene polymorphism in schizophrenics and normal controls, there was no significant difference between two groups. Our results do not support an association between the Bgl I polymorphism of COMT gene and schizophrenia.

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The gene encoding guanidinoacetate methyltransferase (GAMT) maps to mouse chromosome 10 near the locus of hesitant mutation affecting male fertility

  • Chae, Young-Jin;Chung, Chan-Ee;Kim, Byung-Jin;Lee, Mun-Han;Lee, Hang
    • Proceedings of the Korean Society of Developmental Biology Conference
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    • 1998.07a
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    • pp.50-51
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    • 1998
  • guanidinoacetate methyltransferase (GAMT) catalyzes the last step of creatine biosynthesis in mammals. Creatine plays an important role in cellular energy metabolism in variety of tissues including brain and male reproductive tract. Congenital deficiency of the enzyme leads to a neurologic disorder in humans. We used an interspecific backcross DNA panel to map Gamt to the central region of mouse Chromosome (Chr) 10 near the locus of hesitant mutation affecting male fertility. We assigned the human GAMT gene to Chr 19 by PCR analysis of a human/rodent somatic hybrid cell line DNA panel, and further localized the human gene to Chr 19 at band p13.3 by PCR analysis of a human radiation hybrid DNA panel. Human chr 19p13.3 is homologous to the central part of mouse Chr 10 where mouse Gamt is located. Furthermore, this part of mouse Chr 10 contains mutant loci the phenotype of which is similar to the GAMT deficiency in human.

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VaSpoU1 (SpoU gene) may be involved in organelle rRNA/tRNA modification in Viscum album

  • Ahn, Joon-Woo;Kim, Suk-Weon;Liu, Jang-Ryol;Jeong, Won-Joong
    • Plant Biotechnology Reports
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    • v.5 no.3
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    • pp.289-295
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    • 2011
  • The SpoU family of proteins catalyzes the methylation of transfer RNAs (tRNAs) and ribosomal RNAs (rRNAs). We characterized a putative tRNA/rRNA methyltransferase, VaSpoU1 of the SpoU family, from Viscum album (mistletoe). VaSpoU1 and other plant SpoU1s exhibit motifs of the SpoU methylase domain that are conserved with bacterial and yeast SpoU methyltransferases. VaSpoU1 transcripts were detected in the leaves and stems of V. album. VaSpoU1-GFP fusion proteins localized to both chloroplasts and mitochondria in Arabidopsis protoplasts. Sequence analysis similarly predicted that the plant SpoU1 proteins would localize to chloroplasts and mitochondria. Interestingly, mitochondrial localization of VaSpoU1 was inhibited by the deletion of a putative N-terminal presequence in Arabidopsis protoplasts. Therefore, VaSpoU1 may be involved in tRNA and/or rRNA methylation in both chloroplasts and mitochondria.

CRYSTAL STRUCTURE OF tRNA ($m^1$ G37) METHYLTRANSFERASE

  • Ahn, Hyung-Jun;Lee, Byung-Ill;Yoon, Hye-Jin;Yang, Jin-Kuk;Suh, Se-Won
    • Proceedings of the Korea Crystallographic Association Conference
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    • 2003.05a
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    • pp.17-17
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    • 2003
  • tRNA (m¹ G37) methyltransferase (TrmD) catalyze s the trans for of a methyl group from S-adenosyl-L-methionine (AdoMet) to G/sup 37/ within a subset of bacterial tRNA species, which have a residue G at 36th position. The modified guanosine is adjacent to and 3' of the anticodon and is essential for the maintenance of the correct reading frame during translation. We have determined the first crystal structure of TrmD from Haemophilus influenzae, as a binary complex with either AdoMet or S-adenosyl-L-homocysteine (AdoHcy), as a ternary complex with AdoHcy/phosphate, and as an apo form. The structure indicates that TrmD functions as a dimer (Figure 1). It also suggests the binding mode of G/sup 36/G/sup 37/ in the active site of TrmD and catalytic mechanism. The N-terminal domain has a trefoil knot, in which AdoMet or AdoHcy is bound in a novel, bent conformation. The C-terminal domain shows a structural similarity to DNA binding domain of trp or tot repressor. We propose a plausible model for the TrmD₂-tRNA₂ complex, which provides insights into recognition of the general tRNA structure by TrmD (Figure 2).

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The Homodimerization of Thalictrum tuberosum O-Methyltransferases by Homology-based Modelling

  • Yang, Hee-Jung;Ahn, Joong-Hoon;Jeong, Karp-Joo;Lee, Sang-San;Lim, Yoong-Ho
    • Bulletin of the Korean Chemical Society
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    • v.24 no.9
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    • pp.1256-1260
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    • 2003
  • Two O-methyltransferases, OMTII-1 and OMTII-4 of meadow rue Thalictrum tuberosum showed a high sequence identity. Of 364 amino acids only one residue is not the same, which is Tyr21 or Cys21. Even if the 21st residues in these OMTs are not included in the binding sites of the enzymes, binding affinities of the enzyme homodimers over the same substrate are very different. While the binding affinity of one homodimer over caffeic acid is 100%, that of the other is 25%. Authors tried to predict the three-dimensional structures of Thalictrum tuberosum O-methyltransferases using homology-based modelling by a comparison with caffeic acid O-methyltransferase, and explain the reason of the phenomenon mentioned above based on their three dimensional structural studies. In the enzyme homodimer, the better binding affinity may be caused by the shorter distance between the 21st residue and the binding site of the other monomer.

Flavonoids can be Potent Inhibitors of Human Phenylethanolamine N-Methyltransferase (hPNMT)

  • Lee, Jee-Young;Jeong, Ki-Woong;Kim, Yang-Mee
    • Bulletin of the Korean Chemical Society
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    • v.30 no.8
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    • pp.1835-1838
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    • 2009
  • Inhibition of human phenylethanolamine N-methyltransferase (hPNMT) has been proposed as a method for the treatment of several mental processes which related on adrenaline metabolism. We performed in silico screening to identify flavonoid inhibitors of hPNMT using automated docking method and selected 9 inhibitor candidates based on ligand score (LigScore) and binding free energy (${\Delta}G_{bind}$) estimation. Among 9 flavonoid candidates, 7 flavonoids belong to flavones while the rest of them belong to flavanone. All candidates have common chemical features; two hydrogen bond interactions with side chain of Lys75 and backbone carbonyl oxygen of Asn39, and two hydrophobic interactions. One hydrophobic site is formed by Val53, Leu262, and Met258 and the other is made up of Phe182, Ala186, Tyr222, and Val269. This study can be helpful to understand the structural features for inhibition of PNMT and showed flavonoids as promising inhibitor candidates for hPNMT.

Molecular Cloning and Characterization of Bacillus cereus O-Methyltransferase

  • Lee Hyo-Jung;Kim Bong-Gyu;Ahn Joong-Hoon
    • Journal of Microbiology and Biotechnology
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    • v.16 no.4
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    • pp.619-622
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    • 2006
  • Biotransformation is a good tool to synthesize regioselective compounds. It could be performed with diverse sources of genes, and microorganisms provide a myriad of gene sources for biotransformation. We were interested in modification of flavonoids, and therefore, we cloned a putative O-methyltransferase from Bacillus cereus, BcOMT-2. It has a 668-bp open reading frame that encodes a 24.6-kDa protein. In order to investigate the modification reaction mediated by BcOMT-2, it was expressed in E. coli as a His-tag fusion protein and purified to homogeneity. Several substrates such as naringenin, luteolin, kaempferol, and quercetin were tested and reaction products were analyzed by thin layer chromatography (TLC) and high performance liquid chromatography (HPLC). BcOMT-2 could transfer a methyl group to substrates that have a 3' functional hydroxyl group, such as luteolin and quercetin. Comparison of the HPLC retention time and UV spectrum of the quercetin reaction product with corresponding authentic 3'-methylated and 4'-methylated compounds showed that the methylation position was at either the 3'-hydroxyl or 4'-hydroxyl group. Thus, BcOMT-2 transfers a methyl group either to the 3'-hydroxyl or 4'-hydroxyl group of flavonoids when both hydroxyl groups are available. Among several flavonoids that contain a 3'- and 4'-hydroxyl group, fisetin was the best substrate for the BcOMT-2.