Kon Ho Lee

Gyeongsang National University, Chinju, South Gyeongsang, South Korea

Are you Kon Ho Lee?

Claim your profile

Publications (34)87.83 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Escherichia coli 6-carboxytetrahydropterin synthase (eCTPS), a homologue of 6-pyruvoyltetrahydropterin synthase (PTPS), possesses a much stronger catalytic activity to cleave the side chain of sepiapterin in vitro compared with genuine PTPS activity and catalyzes the conversion of dihydroneopterin triphosphate to 6-carboxy-5,6,7,8-tetrahydropterin in vivo. Crystal structures of wild-type apo eCTPS and of a Cys27Ala mutant eCTPS complexed with sepiapterin have been determined to 2.3 and 2.5 Å resolution, respectively. The structures are highly conserved at the active site and the Zn(2+) binding site. However, comparison of the eCTPS structures with those of mammalian PTPS homologues revealed that two specific residues, Trp51 and Phe55, that are not found in mammalian PTPS keep the substrate bound by stacking it with their side chains. Replacement of these two residues by site-directed mutagenesis to the residues Met and Leu, which are only found in mammalian PTPS, converted eCTPS to the mammalian PTPS activity. These studies confirm that these two aromatic residues in eCTPS play an essential role in stabilizing the substrate and in the specific enzyme activity that differs from the original PTPS activity. These aromatic residues Trp51 and Phe55 are a key signature of bacterial PTPS enzymes that distinguish them from mammalian PTPS homologues.
    Acta Crystallographica Section D Biological Crystallography 05/2014; 70(Pt 5):1212-23. · 12.67 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A UDP-glucose:tetrahydrobiopterin α-glucosyltransferase (BGluT) enzyme was discovered in the cyanobacterium Synechococcus sp. PCC 7942 which transfers a glucose moiety from UDP-glucose to tetrahydrobiopterin (BH4). BGluT protein was overexpressed with selenomethionine labelling for structure determination by the multi-wavelength anomalous dispersion method. The BGluT protein was purified by nickel-affinity and size-exclusion chromatography. It was then crystallized by the hanging-drop vapour-diffusion method using a well solution consisting of 0.1 M bis-tris pH 5.5, 19%(w/v) polyethylene glycol 3350 with 4%(w/v) D(+)-galactose as an additive. X-ray diffraction data were collected to 1.99 Å resolution using a synchrotron-radiation source. The crystals belonged to the monoclinic space group C2, with unit-cell parameters a = 171.35, b = 77.99, c = 53.77 Å, β = 90.27°.
    Acta crystallographica. Section F, Structural biology communications. 02/2014; 70(Pt 2):203-5.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Tribulus terrestris fruits are well known for their usage in pharmaceutical preparations and food supplements. The methanol extract of T. terrestris fruits showed potent inhibition against the papain-like protease (PLpro), an essential proteolylic enzyme for protection to pathogenic virus and bacteria. Subsequent bioactivity-guided fractionation of this extract led to six cinnamic amides (1-6) and ferulic acid (7). Compound 6 emerged as new compound possessing the very rare carbinolamide motif. These compounds (1-7) were evaluated for severe acute respiratory syndrome coronavirus (SARS-CoV) PLpro inhibitory activity to identify their potencies and kinetic behavior. Compounds (1-6) displayed significant inhibitory activity with IC50 values in the range 15.8-70.1 µM. The new cinnamic amide 6 was found to be most potent inhibitor with an IC50 of 15.8 µM. In kinetic studies, all inhibitors exhibited mixed type inhibition. Furthermore, the most active PLpro inhibitors (1-6) were proven to be present in the native fruits in high quantities by HPLC chromatogram and liquid chromatography with diode array detection and electrospray ionization mass spectrometry (LC-DAD-ESI/MS).
    Biological & Pharmaceutical Bulletin 01/2014; 37(6):1021-8. · 1.85 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: CsStefin-2, the second cysteine protease inhibitor of Clonorchis sinensis, was identified and characterized. CsStefin-2 is a cysteine protease inhibitor that belongs to family 1 stefins based on its phylogenetic and structural properties. However, CsStefin-2 had a QIVSG cystatin motif distinct from the common QVVAG cystatin motif that is well conserved in family 1 stefins. Mutagenesis analysis revealed that the two amino acid substitutions in the QIVSG cystatin motif of CsStefin-2 did not affect its inhibitory activity. Molecular modeling also indicated that no critical change was induced in the interaction between CsStefin-2 and its target enzyme. CsStefin-2 showed broad inhibitory activities against several cysteine proteases, including human cathepsins B and L, papain, and cathepsin Fs of C. sinensis (CsCFs), and effectively inhibited the autocatalytic maturation of CsCF-6. Native CsStefin-2 was assembled into a homo-tetramer, in which intermolecular disulfide bonds are not involved in the assembly of the tetramer. CsStefin-2 was expressed throughout the various developmental stages of the parasite and was localized in the intestinal epithelium, where CsCFs are actively synthesized. These results suggest that CsStefin-2 is the second active cysteine protease inhibitor of C. sinensis that shares functional redundancy with CsStefin-1 to modulate the activity and processing of CsCFs.
    Parasitology Research 10/2013; · 2.85 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: SARS-CoV papain-like protease (PLpro) is an important antiviral target due to its key roles in SARS virus replication. The MeOH extracts of the fruits of the Paulownia tree yielded many small molecules capable of targeting PLpro. Five of these compounds were new geranylated flavonoids, tomentin A, tomentin B, tomentin C, tomentin D, tomentin E (1-5). Structure analysis of new compounds (1-5) by NMR showed that they all contain a 3,4-dihydro-2H-pyran moiety. This chemotype is very rare and is derived from cyclization of a geranyl group with a phenol functionality. Most compounds (1-12) inhibited PLpro in a dose dependent manner with IC50's raging between 5.0 and 14.4μM. All new compounds having the dihydro-2H-pyran group showed better inhibition than their parent compounds (1 vs 11, 2 vs 9, 4 vs 12, 5 vs 6). In kinetic studies, 1-12 emerged to be reversible, mixed inhibitors.
    Bioorganic & medicinal chemistry 03/2013; · 2.82 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Abstract Severe acute respiratory syndrome coronavirus (SARS-CoV) papain-like protease (PLpro) is a key enzyme that plays an important role in SARS virus replication. The ethanol extract of the seeds of Psoralea corylifolia showed high activity against the SARS-CoV PLpro with an IC(50) of value of 15 µg/ml. Due to its potency, subsequent bioactivity-guided fractionation of the ethanol extract led to six aromatic compounds (1-6), which were identified as bavachinin (1), neobavaisoflavone (2), isobavachalcone (3), 4'-O-methylbavachalcone (4), psoralidin (5) and corylifol A (6). All isolated flavonoids (1-6) inhibited PLpro in a dose-dependent manner with IC(50) ranging between 4.2 and 38.4 µM. Lineweaver-Burk and Dixon plots and their secondary replots indicated that inhibitors (1-6) were mixed inhibitors of PLpro. The analysis of K(I) and K(IS) values proved that the two most promising compounds (3 and 5) had reversible mixed type I mechanisms.
    Journal of Enzyme Inhibition and Medicinal Chemistry 01/2013; · 1.50 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Cel5A, an endoglucanase, was derived from the metagenomic library of vermicompost. The deduced amino acid sequence of Cel5A shows high sequence homology with family-5 glycoside hydrolases, which contain a single catalytic domain but no distinct cellulose-binding domain. Random mutagenesis and cellulose-binding module (CBM) fusion approaches were successfully applied to obtain properties required for cellulose hydrolysis. After two rounds of error-prone PCR and screening of 3,000 mutants, amino acid substitutions were identified at various positions in thermotolerant mutants. The most heat-tolerant mutant, Cel5A_2R2, showed a 7-fold increase in thermostability. To enhance the affinity and hydrolytic activity of Cel5A on cellulose substrates, the family-6 CBM from Saccharophagus degradans was fused to the C-terminus of the Cel5A_2R2 mutant using overlap PCR. The Cel5A_2R2-CBM6 fusion protein showed 7-fold higher activity than the native Cel5A on Avicel and filter paper. Cellobiose was a major product obtained from the hydrolysis of cellulosic substrates by the fusion enzyme, which was identified by using thin layer chromatography analysis.
    PLoS ONE 01/2013; 8(6):e65727. · 3.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Mevalonate kinase (MVK), which plays an important role in catalysing the biosynthesis of isoprenoid compounds derived from the mevalonate pathway, transforms mevalonate to 5-phosphomevalonate using ATP as a cofactor. Mevalonate kinase from Methanosarcina mazei (MmMVK) was expressed in Escherichia coli, purified and crystallized for structural analysis. Diffraction-quality crystals of MmMVK were obtained by the vapour-diffusion method using 0.32 M MgCl(2), 0.08 M bis-tris pH 5.5, 16%(w/v) PEG 3350. The crystals belonged to space group P2(1)2(1)2, with unit-cell parameters a = 97.11, b = 135.92, c = 46.03 Å. Diffraction data were collected to 2.08 Å resolution.
    Acta Crystallographica Section F Structural Biology and Crystallization Communications 12/2012; 68(Pt 12):1560-3. · 0.55 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We have studied the regulatory function of Dictyostelium discoideum Ax2 phenylalanine hydroxylase (dicPAH) via characterization of domain structures. Including the full-length protein, partial proteins truncated in regulatory, tetramerization, or both, were prepared from Escherichia coli as his-tag proteins and examined for oligomeric status and catalytic parameters for phenylalanine. The proteins were also expressed extrachromosomally in the dicPAH knockout strain to examine their in vivo compatibility. The results suggest that phenylalanine activates dicPAH, which is functional in vivo as a tetramer, although cooperativity was not observed. In addition, the results of kinetic study suggest that the regulatory domain of dicPAH may play a role different from that of the domain in mammalian PAH. STRUCTURED SUMMARY OF PROTEIN INTERACTIONS: dicPAH and dicPAHbind by molecular sieving (View Interaction: 1, 2, 3, 4).
    FEBS letters 09/2012; 586(20):3596-600. · 3.54 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Cinnamyl alcohol dehydrogenase is a zinc- and NADPH-dependent dehydrogenase catalyzing the reversible conversion of p-hydroxycinnamaldehydes to their corresponding hydroxycinnamyl alcohols. A CAD homolog from Helicobacter pylori (HpCAD) possesses broad substrate specificities like the plant CADs and additionally a dismutation activity converting benzaldehyde to benzyl alcohol and benzoic acid. We have determined the crystal structure of HpCAD complexed with NADP(H) at 2.18Å resolution to get a better understanding of this class of CAD outside of plants. The structure of HpCAD is highly homologous to the sinapyl alcohol dehydrogenase and the plant CAD with well-conserved residues involved in catalysis and zinc binding. However, the NADP(H) binding mode of the HpCAD has been found to be significantly different from those of plant CADs.
    FEBS letters 02/2012; 586(4):337-43. · 3.54 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A DJ-1 homologue protein from Arabidopsis thaliana (AtDJ-1D) belongs to the DJ-1/ThiJ/Pfpl superfamily and contains two tandem arrays of DJ-1-like sequences, but no structural information is available to date for this protein. AtDJ-1D was expressed in Escherichia coli, purified and crystallized for structural analysis. A crystal of AtDJ-1D was obtained by the hanging-drop vapour-diffusion method using 0.22 M NaCl, 0.1 M bis-tris pH 6.5, 21% polyethylene glycol 3350. AtDJ-1D crystals belonged to the monoclinic space group P2(1), with unit-cell parameters a = 56.78, b = 75.21, c = 141.68 Å, β = 96.87°, and contained a trimer in the asymmetric unit. Diffraction data were collected to 2.05 Å resolution. The structure of AtDJ-1D has been determined using the multiple-wavelength anomalous dispersion (MAD) method.
    Acta Crystallographica Section F Structural Biology and Crystallization Communications 01/2012; 68(Pt 1):101-4. · 0.55 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Up to now, d-threo-tetrahydrobiopterin (DH(4), dictyopterin) was detected only in Dictyostelium discoideum, while the isomer L-erythro-tetrahydrobioterin (BH(4)) is common in mammals. To elucidate the mechanism of DH(4) regeneration by D. discoideum dihydropteridine reductase (DicDHPR), we have determined the crystal structure of DicDHPR complexed with NAD(+) at 2.16 Å resolution. Significant structural differences from mammalian DHPRs are found around the coenzyme binding site, resulting in a higher K(m) value for NADH (K(m)=46.51±0.4 μM) than mammals. In addition, we have found that rat DHPR as well as DicDHPR could bind to both substrates quinonoid-BH(2) and quinonoid-DH(2) by docking calculations and have confirmed their catalytic activity by in vitro assay.
    FEBS letters 07/2011; 585(17):2640-6. · 3.54 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The mouse model is alleged to be a useful tool for understanding of pathophysiological roles of Helicobacter pylori in the development of gastric disorders. However, it has been observed that H. pylori strains significantly differed in their fitness in mice and even mouse strains differed in their susceptibilities to a H. pylori strain. Bacterial components of H. pylori which could affect on its fitness in mice have to be elucidated for the establishment of the mouse model for H. pylori infections. In the comparison of colonization ability between two H. pylori Korean isolates, 51 (isolated from a patient with duodenal ulcer) and 52 (isolated from a patient with gastric cancer), 52 could colonize better than 51 on the gastric mucosa of mouse. Proteome components of H. pylori 52, as a good colonizer and H. pylori 51, as a poor one were quantitatively compared each other. Five bacterial proteins including catalase, urease subunit alpha/beta, enolase and ferritin, were up-regulated in 52. In addition, the respective proteome components of the two strains were also compared with their mouse-passaged homologous strains. Seven and five proteins, which included catalase, flagellin A/B in common, were up-regulated in mouse-adapted 51 and 52, respectively. Among the fourteen identified proteins, urease subunit alpha/beta, flagellin A/B, catalase, ferritin, superoxide dismutase and neutrophil-activation protein have been previously known to be necessary to gastric colonization of H. pylori in animal models. The other up-regulated proteins including enolase, elongation factor Tu and fructose-bisphosphate aldolase have been reported to be associated with acid tolerance of H. pylori. These data provide confirmatory evidence for the importance of those proteins in the development of H. pylori-associated gastric disorders.
    Journal of Bacteriology and Virology 01/2011; 41(4).
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Here, we report cloning of cyanobacterial genes encoding pteridine glycosyltransferases that catalyze glucosyl or xylosyl transfer from UDP-sugars to tetrahydrobiopterin. The genes were cloned by PCR amplification from genomic DNA which was isolated from culture and environmental samples and overexpressed in Escherichia coli for an in vitro activity assay.
    Applied and Environmental Microbiology 11/2010; 76(22):7658-61. · 3.95 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Dictyostelium discoideum phenylalanine hydroxylase (DicPAH; residues 1-415) was expressed in Escherichia coli and purified for structural analysis. Apo DicPAH and DicPAH complexed with dihydrobiopterin (BH(2)) and Fe(III) were crystallized using 0.06 M PIPES pH 7.0, 26%(w/v) PEG 2000 by the hanging-drop vapour-diffusion method. Crystals of apo DicPAH and the DicPAH-BH(2)-Fe(III) complex diffracted to 2.6 and 2.07 A resolution, respectively, and belonged to space group P2(1), with unit-cell parameters a = 70.02, b = 85.43, c = 74.86 A, beta = 110.12 degrees and a = 70.97, b = 85.33, c = 74.89 A, beta = 110.23 degrees , respectively. There were two molecules in the asymmetric unit. The structure of DicPAH has been solved by molecular replacement.
    Acta Crystallographica Section F Structural Biology and Crystallization Communications 04/2010; 66(Pt 4):463-6. · 0.55 Impact Factor
  • Source
    Journal of Bacteriology and Virology 01/2010; 40(2).
  • [Show abstract] [Hide abstract]
    ABSTRACT: Hsp90 proteins are essential molecular chaperones regulating multiple cellular processes in distinct subcellular organelles. In this study, we report the functional characterization of a cDNA encoding endoplasmic reticulum (ER)-resident Hsp90 from orchardgrass (DgHsp90). DgHsp90 is a 2742bp cDNA with an open reading frame predicted to encode an 808 amino acid protein. DgHsp90 has a well conserved N-terminal ATPase domain and a C-terminal Hsp90 domain and ER-retention motif. Expression of DgHsp90 increased during heat stress at 35 degrees C or H(2)O(2) treatment. DgHsp90 also functions as a chaperone protein by preventing thermal aggregation of malate dehydrogenase (EC 1.1.1.37) and citrate synthase (EC 2.3.3.1). The intrinsic ATPase activity of DgHsp90 was inhibited by geldanamycin, an Hsp90 inhibitor, and the inhibition reduced the chaperone activity of DgHsp90. Yeast cells overexpressing DgHsp90 exhibited enhanced thermotolerance.
    Plant Physiology and Biochemistry 07/2009; 47(10):859-66. · 2.78 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Dihydropteridine reductase from Dictyostelium discoideum (dicDHPR) can produce D-threo-BH(4) [6R-(1'R,2'R)-5,6,7,8-tetrahydrobiopterin], a stereoisomer of L-erythro-BH(4), in the last step of tetrahydrobiopterin (BH(4)) recycling. In this reaction, DHPR uses NADH as a cofactor to reduce quinonoid dihydrobiopterin back to BH(4). To date, the enzyme has been purified to homogeneity from many sources. In this report, the dicDHPR-NAD complex has been crystallized using the hanging-drop vapour-diffusion method with PEG 3350 as a precipitant. Rectangular-shaped crystals were obtained. Crystals grew to maximum dimensions of 0.4 x 0.6 x 0.1 mm. The crystal belonged to space group P2(1), with unit-cell parameters a = 49.81, b = 129.90, c = 78.76 A, beta = 100.00 degrees , and contained four molecules in the asymmetric unit, forming two closely interacting dicDHPR-NAD dimers. Diffraction data were collected to 2.16 A resolution using synchrotron radiation. The crystal structure has been determined using the molecular-replacement method.
    Acta Crystallographica Section F Structural Biology and Crystallization Communications 12/2008; 64(Pt 11):1013-5. · 0.55 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: p23 is a heat shock protein 90 (Hsp90) co-chaperone and stabilizes the Hsp90 heterocomplex in mammals and yeast. In this study, we isolated a complementary DNA (cDNA) encoding p23 from orchardgrass (Dgp23) and characterized its functional roles under conditions of thermal stress. Dgp23 is a 911 bp cDNA with an open reading frame predicted to encode a 180 amino acid protein. Northern analysis showed that expression of Dgp23 transcripts was heat inducible. Dgp23 has a well-conserved p23 domain and interacted with an orchardgrass Hsp90 homolog in vivo, like mammalian and yeast p23 homologs. Recombinant Dgp23 is a small acidic protein with a molecular mass of approximately 27 kDa and pI 4.3. Dgp23 was also shown to function as a chaperone protein by suppression of malate dehydrogenase thermal aggregation. Differential scanning calorimetry thermograms indicated that Dgp23 is a heat-stable protein, capable of increasing the T (m) of lysozyme. Moreover, overexpression of Dgp23 in a yeast p23 homolog deletion strain, Deltasba1, increased cell viability. These results suggest that Dgp23 plays a role in thermal stress-tolerance and functions as a co-chaperone of Hsp90 and as a chaperone.
    Cell Stress and Chaperones 10/2008; 14(3):233-43. · 2.48 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Sepiapterin reductase from Chlorobium tepidum (cSR) catalyzes the synthesis of a distinct tetrahydrobiopterin (BH4), L-threo-BH4, different from the mammalian enzyme product. The 3-D crystal structure of cSR has revealed that the product configuration is determined solely by the substrate binding mode within the well-conserved catalytic triads. In cSR, the sepiapterin is stacked between two aromatic side chains of Phe-99 and Trp-196 and rotated approximately 180 degrees C around the active site from the position in mouse sepiapterin reductase. To confirm their roles in substrate binding, we mutated Phe-99 and/or Trp-196 to alanine (F99A, W196A) by site-directed mutagenesis and comparatively examined substrate binding of the purified proteins by kinetics analysis and differential scanning calorimetry. These mutants had higher Km values than the wild type. Remarkably, the W196A mutation resulted in a higher Km increase compared with the F99A mutation. Consistent with the results, the melting temperature (Tm) in the presence of sepiapterin was lower in the mutant proteins and the worst was W196A. These findings indicate that the two residues are indispensable for substrate binding in cSR, and Trp-196 is more important than Phe-99 for different stereoisomer production.
    Acta Biochimica et Biophysica Sinica 07/2008; 40(6):513-8. · 1.81 Impact Factor

Publication Stats

187 Citations
87.83 Total Impact Points

Institutions

  • 2005–2013
    • Gyeongsang National University
      • • Institute of Agriculture and Life Science
      • • Department of Microbiology
      • • Division of Applied Life Science
      • • Plant Molecular Biology and Biotechnology Research Center
      Chinju, South Gyeongsang, South Korea
  • 2006–2012
    • Inje University
      • School of Biotechnology and Biomedical Science
      Kŭmhae, South Gyeongsang, South Korea