• BMB Reports
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• v.35 no.4
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• pp.437-441
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• 2002

Dihydrolipoamide dehydrogenase (E3) is a member of the pyridine nucleotide-disulfide oxidoreductase family. Thr residues are highly conserved. They are at the active site disulfide-bond regions of most E3s and other oxidoreductases,. The crystal structure of Azotobacter vinelandii E3 suggests that the hydroxyl group of Thr that are involved in the FAD binding interact with the adenosine phosphate of FAD. However, several prokaryotic E3s have Val instead of Thr. To investigate the meaning and importance of the Thr conservation in many E3s, the corresponding residue, Thr-44, in human E3 was substituted to Val by site-directed mutagenesis. The mutant’s E3 activity showed about a 2.2-fold decrease. Its UV-visible and fluorescence spectra indicated that the mutant might have a slightly different microenvironment at the FAD-binding region.

• BMB Reports
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• v.49 no.4
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• pp.201-207
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• 2016

The CRISPR-Cas system has emerged as a fascinating and important genome editing tool. It is now widely used in biology, biotechnology, and biomedical research in both academic and industrial settings. To improve the specificity and efficiency of Cas nucleases and to extend the applications of these systems for other areas of research, an understanding of their precise working mechanisms is crucial. In this review, we summarize current studies on the molecular structures and dynamic functions of type I and type II Cas nucleases, with a focus on target DNA searching and cleavage processes as revealed by single-molecule observations.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.729-732
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• 2002

This paper reports an experimental study around a module about forced air flow by blower($35{\times}35{\times}6mm^3$) in portable PC(10mm high, 200mm wide, and 235mm long). The channel inlet flow velocity has been varied between 0.26, 0.52 and 0.78m/s. The power input to the module is 4Wthis report, particular attention is directed to the fluid flow and adiabatic wall temperature($T_(ad)$) around a module which is under fluid mechanical and thermal influences of the module. The fluid flow around a module was visualized using PIV system. Liquid crystal thernography is used to determine the adiabatic wall temperature around a heated module on an acrylic board. Plots of $T_(ad)$ (or F) show marked effects of dispersion of thermal wake near the module.

• BMB Reports
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• v.41 no.5
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• pp.353-357
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• 2008

LRR family proteins play important roles in a variety of physiological processes. To facilitate their production and crystallization, we have invented a novel method termed "Hybrid LRR Technique". Using this technique, the first crystal structures of three TLR family proteins could be determined. In this review, design principles and application of the technique to protein crystallization will be summarized. For crystallization of TLRs, hagfish VLR receptors were chosen as the fusion partners and the TLR and the VLR fragments were fused at the conserved LxxLxLxxN motif to minimize local structural incompatibility. TLR-VLR hybridization did not disturb structures and functions of the target TLR proteins. The Hybrid LRR Technique is a general technique that can be applied to structural studies of other LRR proteins. It may also have broader application in biochemical and medical application of LRR proteins by modifying them without compromising their structural integrity.

• BMB Reports
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• v.55 no.9
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• pp.439-446
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• 2022

Pyridoxal 5'-phosphate (PLP)-dependent enzymes are ubiquitous, catalyzing various biochemical reactions of approximately 4% of all classified enzymatic activities. They transform amines and amino acids into important metabolites or signaling molecules and are important drug targets in many diseases. In the crystal structures of PLP-dependent enzymes, organic cofactor PLP showed diverse conformations depending on the catalytic step. The conformational change of PLP is essential in the catalytic mechanism. In the study, we review the sophisticated catalytic mechanism of PLP, especially in transaldimination reactions. Most drugs targeting PLP-dependent enzymes make a covalent bond to PLP with the transaldimination reaction. A detailed understanding of organic cofactor PLP will help develop a new drug against PLP-dependent enzymes.

• Bulletin of the Korean Chemical Society
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• v.27 no.5
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• pp.747-750
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• 2006

Research on tripodal complexes has grown in recent decades and has been subject of numerous reports.1-11 The reasons for this interest include their relevance to model functions of metalloenzymes1-3 and their potential applications in catalysis.13-17 The ligand system used most in this category has been tren, the tripodal tetraamine N(CH2CH2NH2)3, and its derivatives.4 The bz3tren is a versatile tetradentate ligand, known to form stable complexes not only with transition metals5-11 including Cu2+, Zn2+ and Co2+ but also anion species.12 However, only few results on the d10 metal complexes with bz3tren have been reported by us10 and others.6,7 As a part of on going efforts, we therefore focus our attention to extend other d10 system that includes heavy metal ions.

• BMB Reports
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• v.40 no.1
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• pp.58-64
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• 2007

Similar to the other known structures of Bacillus thuringiensis Cry $\delta$-endotoxins, the crystal structure of the 65-kDa activated Cry4Ba toxin comprises three domains which are, from the N- to C-terminus, a bundle of $\alpha$-helices, a three-$\beta$-sheet domain, and a $\beta$-sandwich. To investigate the properties of the C-terminal domain III in isolation from the rest of the toxin, the cloned Cry4Ba-domain III was over-expressed as a 21-kDa soluble protein in Escherichia coli, which cross-reacted with anti-Cry4Ba domain III monoclonal antibody. A highly-purified domain III was obtained in a monomeric form by ion-exchange and size-exclusion FPLC. Circular dichroism spectroscopy indicated that the isolated domain III fragment distinctly exists as a $\beta$-sheet structure, corresponding to the domain III structure embodied in the Cry4Ba crystal structure. In vitro binding analysis via immuno-histochemical assay revealed that the Cry4Ba-domain III protein was able to bind to the apical microvilli of the susceptible Stegomyia aegypti larval midguts, albeit at lower-binding activity when compared with the full-length active toxin. These results demonstrate for the first time that the C-terminal domain III of the Cry4Ba mosquito-larvicidal protein, which can be isolated as a native folded monomer, conceivably participates in toxin-receptor recognition.

• Korean Journal of Materials Research
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• v.12 no.6
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• pp.488-492
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• 2002

Magnetic properties of nanostructured materials are affected in complicated manner by their microstructure such as grain size, internal strain and crystal structure. Thus, studies on the synthesis of nanostructured materials with controlled microstructure are necessary for a significant improvement in magnetic properties. It is well known that when Fe-Co alloy undergoes ordering transformation, soft magnetic properties could be obtained. There are many reports that the magnetic properties of the materials can be changed with variation of grain size. In the present work, nanostructured Fe-50at.%Co alloy powder produced by hydrogen reduction process (HRP) starting with two oxide powder mixtures of $Fe_2O_3\;and\; Co_3O_4$. The mean grain size of the HRP powders was about 40 nm and coercivity of the: powders was about 43 Oe.

• BMB Reports
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• v.41 no.1
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• pp.48-54
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• 2008

PM0188 is a newly identified sialyltransferase from P. multocida which transfers sialic acid from cytidine 5'-monophosphonuraminic acid (CMP-NeuAc) to an acceptor sugar. Although sialyltransferases are involved in important biological functions like cell-cell recognition, cell differentiation and receptor-ligand interactions, little is known about their catalytic mechanism. Here, we report the X-ray crystal structures of PM0188 in the presence of an acceptor sugar and a donor sugar analogue, revealing the precise mechanism of sialic acid transfer. Site-directed mutagenesis, kinetic assays, and structural analysis show that Asp141, His311, Glu338, Ser355 and Ser356 are important catalytic residues; Asp141 is especially crucial as it acts as a general base. These complex structures provide insights into the mechanism of sialyltransferases and the structure-based design of specific inhibitors.

• Korean Journal of Materials Research
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• v.25 no.12
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• pp.708-712
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• 2015

This study reports the effects of $H_2S$ gas concentration on the properties of $Cu_2ZnSnS_4(CZTS)$ thin films. Specifically, sulfurization process with low $H_2S$ concentrations of 0.05% and 0.1%, along with 5% $H_2S$ gas, was studied. CZTS films were directly synthesized on Mo/Si substrates by chemical bath deposition method using copper sulfate, zinc sulfate heptahydrate, tin chloride dihydrate, and sodium thiosulfate pentahydrate. Smooth CZTS films were grown on substrates at optimized chemical bath deposition condition. The CZTS films sulfurized at low $H_2S$ concentrations of 0.05 % and 0.1% showed very rough and porous film morphology, whereas the film sulfurized at 5% $H_2S$ yielded a very smooth and dense film morphology. The CZTS films were fully crystallized in kesterite crystal form when they were sulfurized at $500^{\circ}C$ for 1 h. The kesterite CZTS film showed a reasonably good room-temperature photoluminescence spectrum that peaked in a range of 1.4 eV to 1.5 eV, consistent with the optimal bandgap for CZTS solar cell applications.