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Biomedical subjects

Myung Hee Kim

Publications and source records attributed to Myung Hee Kim.

At least 19 recordsLinked to original sources
PubMed2007

The changes in coagulation profile and epidural catheter safety for living liver donors: a report on 6 years of our experience.

The use of epidural catheters has been a subject of active debate in living liver donors because of the possible postoperative coagulation derangement and the subsequent risk of epidural hematoma. The aim of this study was to evaluate the safety of epidural catheters in relation to the changes in coagulation profile based on a review of previously published literature and the results of our 360 donors. In both the literature and in our cases, platelet count, prothrombin time (PT), and activated partial thromboplastin time (aPTT) in cases of heparin administration showed significant changes (P < 0.05), especially after right lobectomy. Platelet count reached its nadir on postoperative day (POD) 2-3, while PT and aPTT reached their peaks on POD 1-2 and at the end of the operation, respectively. In our donors, the ranges of platelet count, PT, and aPTT for the first 3 PODs were 54-359 x10/microL, 0.99-2.38 international normalized ratio (INR), and 25.9-300 seconds, respectively, and of note, 5 donors (1.4%) had a platelet count of <80 x 10/microL and 9 donors (2.5%) had a PT of >2.0 INR. Epidural catheterizations were performed in 242 donors, and the catheters were removed on POD 3-4 in 177 donors (73.1%). Mean (range) of platelet count, PT, and aPTT on the day of catheter removal were 168.4 +/- 42.9 (82-307) x 10/microL, 1.33 +/- 0.18 (0.99-1.93) INR, and 40.9 +/- 4.8 (32.0-70.6) seconds, respectively. No epidural hematoma was observed in this study. In conclusion, the discreet use of epidural catheters in live liver donors, in spite of postoperative coagulation derangements, appears to be safe regardless of the type of hepatectomy performed.

Adult↗
PubMed2006

Crystallization and initial crystallographic characterization of the Corynebacterium glutamicum nitrilotriacetate monooxygenase component A.

Safety and environmental concerns have recently dictated the proper disposal of nitrilotriacetate (NTA). Biodegradation of NTA is initiated by NTA monooxygenase, which is composed of two proteins: component A and component B. The NTA monooxygenase component A protein from Corynebacterium glutamicum was crystallized using the sitting-drop vapour-diffusion method in the presence of ammonium sulfate as the precipitant. X-ray diffraction data were collected to a maximum resolution of 2.5 A on a synchrotron beamline. The crystal belongs to the monoclinic space group C2, with unit-cell parameters a = 111.04, b = 98.51, c = 171.61 A, beta = 101.94 degrees . The asymmetric unit consists of four molecules, corresponding to a packing density of 2.3 A(3) Da(-1). The structure was solved by molecular replacement. Structure refinement is in progress.

Bacterial Proteins↗
PubMed2006

The DC-module of doublecortin: dynamics, domain boundaries, and functional implications.

The doublecortin-like (DC) domains, which usually occur in tandem, constitute novel microtubule-binding modules. They were first identified in doublecortin (DCX), a protein expressed in migrating neurons, and in the doublecortin-like kinase (DCLK). They are also found in other proteins, including the RP1 gene product which-when mutated-causes a form of inherited blindness. We previously reported an X-ray structure of the N-terminal DC domain of DCLK (N-DCLK), and a solution structure of an analogous module of human doublecortin (N-DCX). These studies showed that the DC domain has a tertiary fold closely reminiscent of ubiquitin and similar to several GTPase-binding domains. We now report an X-ray structure of a mutant of N-DCX, in which the C-terminal fragment (residues 139-147) unexpectedly shows an altered, "open" conformation. However, heteronuclear NMR data show that this C-terminal fragment is only transiently open in solution, and assumes a predominantly "closed" conformation. While the "open" conformation may be artificially stabilized by crystal packing interactions, the observed switching between the "open" and "closed" conformations, which shortens the linker between the two DC-domains by approximately 20 A, is likely to be of functional importance in the control of tubulin polymerization and microtubule bundling by doublecortin.

Crystallization↗
PubMed2006

Ca(2+)-inositol phosphate chelation mediates the substrate specificity of beta-propeller phytase.

Inositol phosphates are recognized as having diverse and critical roles in biological systems. In this report, kinetic studies and TLC analysis indicate that beta-propeller phytase is a special class of inositol phosphatase that preferentially recognizes a bidentate (P-Ca(2+)-P) formed between Ca(2+) and two adjacent phosphate groups of its natural substrate phytate (InsP(6)). The specific recognition of a bidentate chelation enables the enzyme to sequentially hydrolyze one of the phosphate groups in a bidentate of Ca(2+)-InsP(6) to yield a myo-inositol trisphosphate (InsP(3)) and three phosphates as the final products. A comparative analysis of (1)H- and (13)C NMR spectroscopy with the aid of 2D NMR confirms that the chemical structure of the final product is myo-Ins(2,4,6)P(3). The catalytic properties of the enzyme suggest a potential model for how the enzyme specifically recognizes its substrate Ca(2+)-InsP(6) and produces myo-Ins(2,4,6)P(3) from Ca(2+)-InsP(6). These findings potentially provide evidence for a selective Ca(2+)-InsPs chelation between Ca(2+) and two adjacent phosphate groups of inositol phosphates.

6-Phytase↗
PubMed2006

Synthesis of novel chemical probes for the study of tanshinone binding proteins.

Novel diazirine or biotin-labeled tanshinone probes were synthesized and evaluated for TRAP inhibitory activity against RANKL-induced osteoclastogenesis in RAW264.7 cells. We found that diazirine-labeled derivatives (18 and 20) are potent inhibitors of RANKL-induced osteoclastogenesis. IC50 values were 18.02 and 15.00 microM, respectively. These probes will be useful reagents for investigating tanshinone-proteins interactions.

Abietanes↗
PubMed2006

MELDB: a database for microbial esterases and lipases.

MELDB is a comprehensive protein database of microbial esterases and lipases which are hydrolytic enzymes important in the modern industry. Proteins in MELDB are clustered into groups according to their sequence similarities based on a local pairwise alignment algorithm and a graph clustering algorithm (TribeMCL). This differs from traditional approaches that use global pairwise alignment and joining methods. Our procedure was able to reduce the noise caused by dubious alignment in the distantly related or unrelated regions in the sequences. In the database, 883 esterase and lipase sequences derived from microbial sources are deposited and conserved parts of each protein are identified. HMM profiles of each cluster were generated to classify unknown sequences. Contents of the database can be keyword-searched and query sequences can be aligned to sequence profiles and sequences themselves.

Amino Acid Sequence↗
PubMed2006

A correlation between low back pain and associated factors: a study involving 772 patients who had undergone general physical examination.

Many factors are associated with the development of low back pain. Among them, exercise, obesity, smoking, age, educational level and stress are the most common. This study examined the association of these factors with low back pain. An additional aim was to determine a procedure for preventing low back pain. This study analyzed the responses to a questionnaire sent to 772 individuals who had undergone a medical examination at this hospital in 2003 and excluded the individuals who had shown symptoms or their test results indicated a particular disease. Assuming that there were no variables, individuals who exercised regularly 3-4 times per week would have a lower chance of having low back pain than those who did not exercise regularly. The analysis revealed that individuals with a college degree or higher education have a lower chance of experiencing low back pain than those with only a high school education or even college drop-outs. When the other variables were constant, age, extent of obesity (body mass index), smoking and level of stress were not found to affect the development of low back pain. The level of education was associated with the development of low back pain. However, regular exercise 3-4 times per week or more would be most effective in reducing the incidence and duration of low back pain.

Adolescent↗
PubMed2005

Mitogenic estrogen metabolites alter the expression of 17beta-estradiol-regulated proteins including heat shock proteins in human MCF-7 breast cancer cells.

Estrogen metabolites are carcinogenic. The comparative mitogenic activities of 17b-estradiol (E2) and four metabolites, 2-hydroxyestradiol (2-OHE2), 4-hydroxyestradiol (4-OHE2), 16a-hydroxyestrone (16a-OHE1) and 2-methoxyestradiol (2-ME), were determined in estrogen receptor(ER)-positive MCF-7 human breast cancer cells. Each of the E2 metabolites caused proliferation of the MCF-7 cells, but only E2 and 16a-OHE1 induced a greater than 20-fold increases in transcripts of the progesterone receptor (PR) gene, a classical ER-mediated gene. This suggests that the mitogenic action of E2 and 16a-OHE1 could result from their effects on gene expression via the ER. E2 metabolites altered the expression of E2-regulated proteins including heat shock proteins (Hsps). 16a-OHE1 and 2-ME as well as E2 increased levels of Hsp56, Hsp60, Hsp90a and Hsp110 transcripts, and the patterns of these inductions resembled that of PR. Hsp56 and Hsp60 protein levels were increased by all the E2 metabolites. Levels of the transcripts of 3 E2-upregulated proteins (XTP3-transactivated protein A, protein disulfide isomerase-associated 4 protein and stathmin 1) and an E2-downregulated protein (aminoacylase 1) were also affected by the E2 metabolites. These results suggest that the altered expression of Hsps (especially Hsp56 and Hsp60) by E2 metabolites such as E2, 16a-OHE1 and 2-ME could be closely linked to their mitogenic action.

Amidohydrolases↗
PubMed2005

The molecular structure and catalytic mechanism of a quorum-quenching N-acyl-L-homoserine lactone hydrolase.

In many Gram-negative bacteria, including a number of pathogens such as Pseudomonas aeruginosa and Erwinia carotovora, virulence factor production and biofilm formation are linked to the quorum-sensing systems that use diffusible N-acyl-L-homoserine lactones (AHLs) as intercellular messenger molecules. A number of organisms also contain genes coding for lactonases that hydrolyze AHLs into inactive products, thereby blocking the quorum-sensing systems. Consequently, these enzymes attract intense interest for the development of antiinfection therapies. However, the catalytic mechanism of AHL-lactonase is poorly understood and subject to controversy. We here report a 2.0-angstroms resolution structure of the AHL-lactonase from Bacillus thuringiensis and a 1.7-angstroms crystal structure of its complex with L-homoserine lactone. Despite limited sequence similarity, the enzyme shows remarkable structural similarities to glyoxalase II and RNase Z proteins, members of the metallo-beta-lactamase superfamily. We present experimental evidence that AHL-lactonase is a metalloenzyme containing two zinc ions involved in catalysis, and we propose a catalytic mechanism for bacterial metallo-AHL-lactonases.

Bacillus thuringiensis↗
PubMed2005

Zinc in lipase L1 from Geobacillus stearothermophilus L1 and structural implications on thermal stability.

Lipase L1 from Geobacillus stearothermophilus L1 contains an unusual extra domain, making a tight intramolecular interaction with the main catalytic domain through a Zn2+-binding coordination. To elucidate the role of the Zn2+, we disrupted the Zn2+-binding site by mutating the zinc-ligand residues (H87A, D61A/H87A, and D61A/H81A/H87A/D238A). The activity vs. temperature profiles of the mutant enzymes showed that the disruption of the Zn2+-binding site resulted in a notable decrease in the optimal temperature for maximal activity from 60 to 45-50 degrees C. The mutations also abolished the Zn2+-induced thermal stabilization. The wild-type enzyme revealed a 34.6-fold increase in stabilization with the addition of Zn2+ at 60 degrees C, whereas the mutant enzymes exhibited no response to Zn2+. Additional circular dichroism spectroscopy studies also confirmed the structural stabilizing role of Zn2+ on lipase L1 at elevated temperatures.

Amino Acid Sequence↗
PubMed2005

Crystallization and preliminary crystallographic analysis of Bacillus thuringiensis AHL-lactonase.

The quorum sensing (QS) systems in Gram-negative bacteria are mostly associated with diffusible N-acyl-L-homoserine lactones (AHLs). AHL-degrading enzymes hydrolyze the AHLs into inactive molecules, thereby blocking the QS systems that are closely linked to virulence factor production and biofilm formation. Consequently, these enzymes have recently attracted intense interest for the development of anti-infection therapies for plants and animals. However, despite significant progress in the investigation of AHL-degrading enzymes, no structure is yet available. Accordingly, this study reports on the expression and purification of the AHL-lactonase from Bacillus thuringiensis subsp. kurstaki HD263, as well as the successful crystallization of the enzyme. High-quality native crystals were obtained and a complete data set collected at 2.0 A resolution. The native crystal was found to belong to the space group P2(1)2(1)2(1), with unit cell parameters a=52.7 A, b=55.9 A, and c=74.1 A and one molecule in the asymmetric unit. MAD data were also collected at 2.4 A resolution for a SeMet-substituted crystal.

Bacillus thuringiensis↗
PubMed2005

Multistage ethanol sclerotherapy of soft-tissue arteriovenous malformations: effect on pulmonary arterial pressure.

PURPOSE: To retrospectively investigate how repeat injections of absolute ethanol in therapeutic doses, required for multisession sclerotherapy of large high-flow soft-tissue arteriovenous malformations (AVMs) in patients with normal cardiopulmonary function, affect pulmonary arterial pressure (PAP). MATERIALS AND METHODS: Study received approval and waiver of informed consent by institutional review board and was conducted in 16 male and 16 female patients with AVMs who underwent repeat sclerotherapy (142 sessions total) with absolute ethanol from July 1997 to December 2003. PAPs were monitored during first session in all patients. In subsequent sessions, PAP was monitored with pulmonary catheter when predicted single dose of ethanol exceeded 3 mL and total amount exceeded 0.25 mL/kg. PAP was measured in 104 sessions. Serum ethanol levels from blood samples obtained at end of each session were reviewed. PAP parameters were analyzed at beginning and end of each session, and highest value was recorded to assess any increase after repeat therapy. Difference between initial and highest PAP values recorded in a session (Delta(max)) was noted to determine any increase during repeat sessions. Possible relationship was reviewed between this value and amount of ethanol used. For sessions without PAP monitoring, mixed model was used for statistical analysis. RESULTS: Total ethanol used was variable. In 43 sessions, highest mean PAP exceeded 25 mm Hg. Incidence of sustained pulmonary hypertension (mean PAP > 25 mm Hg) at end of each session was 30.8% (32 of 104 sessions). Initial PAP parameters did not increase or decrease during repeat sessions. No significant changes in Delta(max) of systolic and mean PAP were observed with increasing number of sessions. Rather, Delta(max) of diastolic PAP was reduced after repeat sessions (P = .03). There was no significant correlation between serum ethanol level and PAP parameters at end of sessions. Relationships between Delta(max) values of systolic, mean, and diastolic PAP and total ethanol used were not significant. CONCLUSION: High incidence of acute pulmonary hypertension was observed in each sclerotherapy session without lasting effect on PAP.

Adolescent↗
PubMed2005

Differences of perioperative liver function, transfusion, and complications according to the type of hepatectomy in living donors.

Numerous living donor hepatectomy are being performed safely. However, donors are still exposed to various complications including hepatic failure. We examined the donor's potential risk and morbidity depending on the type of hepatectomy: left lateral segmentectomy (group LLS, n = 30), left lobectomy (group LL, n = 15), and right lobectomy (group RL, n = 128). The charts and computerized hospital data of 173 donors from March 2000 to September 2003 were retrospectively reviewed. We analyzed liver function tests (LFT), RBC transfusion, and complications. Although the graft weight was greatest, and surgical and anesthetic times were longest in the group RL, there were no significant differences in postoperative hospital stay, RBC transfusion, and major complications among the groups. However, minor complications were significantly higher in group RL than group LLS. Postoperative prothrombin time and total bilirubin were significantly higher in the group RL than the other groups (P < 0.05). Living donor hepatectomy is relatively safe, and it is evidenced by rapid recovery of LFT and low occurrence of major complications. However, noticeable depression of LFT and frequent minor complications occur after hepatectomy, especially RL.

Adult↗
PubMed2005

Effect of ketamine on apoptosis by energy deprivation in astroglioma cells using flow cytometry system.

Apoptosis is a programmed, physiologic mode of cell death that plays an important role in tissue homeostasis. As for the central nervous system, ischemic insults can induce pathophysiologic cascade of apoptosis in neurophils. Impairment of astrocyte functions during brain ischemia can critically influence neuron survival by neuronglia interactions. We aimed to elucidate the protective effect of ketamine on apoptosis by energy deprivation in astrocytes. Ischemic insults was induced with iodoacetate/ carbonylcyanide m-chlorophenylhydrazone (IAA/CCCP) 1.5 mM/20 microm or 150 microm/2 microm for 1 hr in the HTB-15 and CRL-1690 astrocytoma cells. Then these cells were reperfused with normal media or ketamine (0.1 mM) containing media for 1 hr or 24 hr. FITC-annexin-V staining and propidium iodide binding were determined by using flow cytometry. Cell size and granularity were measured by forward and side light scattering properties of flow cytometry system, respectively. An addition of ketamine during reperfusion increased the proportion of viable cells. Ketamine alleviated cell shrinkage and increased granularity during the early period, and ameliorated cell swelling during the late reperfusion period. Ketamine may have a valuable effect on amelioration of early and late apoptosis in the astrocytoma cells, even though the exact mechanism remains to be verified.

Anesthetics, Dissociative↗
PubMed2004

The structure of the N-terminal domain of the product of the lissencephaly gene Lis1 and its functional implications.

Mutations in the Lis1 gene result in lissencephaly (smooth brain), a debilitating developmental syndrome caused by the impaired ability of postmitotic neurons to migrate to their correct destination in the cerebral cortex. Sequence similarities suggest that the LIS1 protein contains a C-terminal seven-blade beta-propeller domain, while the structure of the N-terminal fragment includes the LisH (Lis-homology) motif, a pattern found in over 100 eukaryotic proteins with a hitherto unknown function. We present the 1.75 A resolution crystal structure of the N-terminal domain of mouse LIS1, and we show that the LisH motif is a novel, thermodynamically very stable dimerization domain. The structure explains the molecular basis of a low severity form of lissencephaly.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed2003

A genotype-specific pollen gene associated with self-incompatibility in Lycopersicon peruvianum.

Self-incompatibility is a genetically controlled process used to prevent self-pollination. We report here the characterization of pollen cDNA clones of Lycopersicon peruvianum, and the identification of a genotype-specific pollen factor involved in self-incompatibility. To identify the latter, differential mRNA display RT-PCR was performed on pollen cDNAs from S12Sa and S11Sa genotypes. We isolated four cDNA fragments expressed preferentially in S12Sa pollen, and screened a cDNA library from S12Sa pollen with the four cDNA fragments to isolate the corresponding full length cDNAs. One of the four isolated cDNAs encoded part of an actin depolymerizing factor protein that we named LpADF. LpADF is highly homologous to actin depolymerizing factors of Arabidopsis thaliana, Lilium longiflorum, and Zea mays. RNA blot analysis revealed that LpADF is only expressed in mature pollen of the S12Sa genotype, and is therefore a candidate pollen factor in the gametophyte self-incompatibility system of L. peruvianum.

Amino Acid Sequence↗
PubMed2003

Purification and crystallization of the N-terminal domain from the human doublecortin-like kinase.

The unique doublecortin-like tandem of two homologous domains is found in certain microtubule-associated proteins such as doublecortin (DCX) and doublecortin-like kinase (DCLK). It is responsible for interactions with tubulin/microtubules and regulates microtubule dynamics. Here, the expression and purification of the tandem from human DCLK (residues 49-280) and of the isolated domains (residues 49-154 and 176-280) and the successful crystallization of the N-terminal domain (N-DCLK) are reported. High-quality wild-type crystals were obtained and a complete native data set was collected to 1.5 A resolution. The crystals belong to space group C2, with unit-cell parameters a = 85.98, b = 29.62, c = 40.33 A, beta = 101.3 degrees. Crystals of SeMet-substituted N-DCLK (Leu120Met) were also obtained, but they exhibit the symmetry of space group P2(1), with unit-cell parameters a = 38.81, b = 29.43, c = 40.1 A, beta = 115.7 degrees.

Animals↗