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Dong-Geun Lee

Publications and source records attributed to Dong-Geun Lee.

10 recordsLinked to original sources
PubMed2007

Screening and characterization of a novel fibrinolytic metalloprotease from a metagenomic library.

A metagenomic library was constructed using total genomic DNA extracted from the mud in the west coast of Korea and was used together with a fosmid vector, pCC1FOS in order to uncover novel gene sources. One clone from approximately 30,000 recombinant Escherichia coli clones was identified that showed proteolytic activity. The gene for the proteolytic enzyme was subcloned into pUC19 and sequenced, and a database search for homologies revealed it to be a zinc-dependent metalloprotease. The cloned gene included the intact coding gene for a novel metalloproteinase and its own promoter. It comprised an open reading frame of 1,080 base pairs, which encodes a protein of 39,490 Da consisting of 359 amino acid residues. A His-Glu-X-X-His sequence, which is a conserved sequence in the active site of zinc-dependent metalloproteases, was found in the deduced amino acid sequence of the gene, suggesting that the enzyme is a zinc-dependent metalloprotease. The purified enzyme showed optimal activity at 50 degrees C for 1 h and pH 7.0. The enzyme activity was inhibited by metal-chelating reagents, such as EDTA, EGTA and 1,10-phenanthroline. The enzyme hydrolyzed azocasein as well as fibrin. Thus, the enzyme could be useful as a therapeutic agent to treat thrombosis.

Bacterial Proteins↗
PubMed2006

Cloning, expression, and characterization of a glycoside hydrolase family 50 beta-agarase from a marine Agarivorans isolate.

The gene for a thermostable beta-agarase from Agarivorans sp. JA-1 was cloned and sequenced. It comprised an open reading frame of 2,988 base pairs, which encode a protein of 109,450 daltons consisting of 995 amino acid residues. A comparison of the entire sequence showed that the enzyme has 98.8% sequence similarities to beta-agarase from Vibrio sp. JT1070, indicating that it belongs to the family glycoside hydrolase (GH)-50. The gene corresponding to a mature protein of 976 amino acids was inserted and expressed in Escherichia coli. The recombinant beta-agarase was purified to homogeneity. It had maximal activity at 40 degrees C and pH 8.0 in the presence of 1 mM NaCl and 1 mM CaCl(2). The enzyme hydrolyzed agarose as well as neoagarohexaose and neoagarotetraose to yield neoagarobiose as the main product. Thus, the enzyme would be useful for the industrial production of neoagarobiose.

Amino Acid Sequence↗
PubMed2006

Identification of BRCA1 and BRCA2 mutations from Korean breast cancer patients using denaturing HPLC.

In order to investigate the presence and function of BRCA mutations in Korean breast cancer patients, mutational analyses using denaturing HPLC (DHPLC) were performed for 1020 breast cancer patients and 167 normal females. We identified 14 deleterious mutations that included 10 frameshift mutations and 4 nonsense mutations. Among these 14 mutations, we found 3 novel BRCA1 and 3 novel BRCA2 mutations. We found that BRCA deleterious mutations were present in 19 of the 1020 patients (1.8%). Three of the 14 deleterious mutations were detected in 7 of these 19 patients. The three mutations were also identified in other studies for BRCA mutations in the Korean population, suggesting that they are possible founder mutations of BRCA for the Korean population. We plan to provide fundamental data for larger population-based studies to establish the frequency and significance of BRCA mutations in Korean breast cancer patients.

Base Sequence↗
PubMed2005

Comparative analysis of cortical layering and supragranular layer enlargement in rodent carnivore and primate species.

The mammalian cerebral cortex is composed of individual layers characterized by the cell types they contain and their afferent and efferent connections. The current study examined the raw, and size-normalized, laminar thicknesses in three cortical regions (somatosensory, motor, and premotor) of fourteen species from three orders of mammals: primates, carnivores, and rodents. The proportional size of the pyramidal cell layers (supra- and infragranular) varied between orders but was similar within orders despite wide variance in absolute cortical thickness. Further, supragranular layer thickness was largest in primates (46 +/- 3 percent), followed by carnivores (36 +/- 3 percent), and then rodents (19 +/- 4 percent), suggesting a distinct difference in the proportion of cortex devoted to corticocortical connectivity across these orders. Although measures of supragranular layer thickness are highly correlated with measures of overall brain size, such associations are not present when independent contrasts are used to control for phylogenetic inertia. Interestingly, neurogenesis time span remains strongly associated with supragranular layer thickness despite size normalization and controlling for phylogenetic inertia. Such layering differences between orders, and similarities amongst species within an order, suggest that supragranular layer expansion may have occurred early in mammalian evolution and may be related to ontogenetic variables such as neurogenesis time span rather than measures of overall size.

Animals↗
PubMed2005

Potential of human bone marrow stromal cells to accelerate wound healing in vitro.

The purpose of this pilot study was to compare proliferation, collagen synthesis, and growth factor production, which are important contributing factors for wound healing, of the bone marrow stromal cells (BSCs) with those of dermal fibroblasts in vitro. Cultured human BSCs and dermal fibroblasts from the same patients were seeded in 96-well culture plates. At 1, 3, and 5 days postincubating, cell proliferation, collagen synthesis, and secretion of basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), and transforming growth factor beta (TFG-beta) were compared. We did not observe great differences in cell proliferation and TFG-beta secretion. In contrast, the amount of collagen synthesis and the levels of the bFGF and the VEGF were much higher in the BSC group than the fibroblast group at each time interval (P < 0.05). Our results suggest that the BSCs may have superior potential to accelerate wound healing than the fibroblasts.

Adult↗
PubMed2004

Self-protection mechanism in D-cycloserine-producing Streptomyces lavendulae. Gene cloning, characterization, and kinetics of its alanine racemase and D-alanyl-D-alanine ligase, which are target enzymes of D-cycloserine.

An antibiotic, D-cycloserine (DCS), inhibits the catalytic activities of alanine racemase (ALR) and d-alanyl-d-alanine ligase (DDL), which are necessary for the biosynthesis of the bacterial cell wall. In this study, we cloned both genes encoding ALR and DDL, designated alrS and ddlS, respectively, from DCS-producing Streptomyces lavendulae ATCC25233. Each gene product was purified to homogeneity and characterized. Escherichia coli, transformed with a pET vector carrying alrS or ddlS, displays higher resistance to DCS than the same host carrying the E. coli ALR- or DDL-encoded gene inserted into the pET vector. Although the S. lavendulae DDL was competitively inhibited by DCS, the K(i) value (920 microM) was obviously higher (40 approximately 100-fold) than those for E. coli DdlA (9 microM) or DdlB (27 microM). The high K(i) value of the S. lavendulae DDL suggests that the enzyme may be a self-resistance determinant in the DCS-producing microorganism. Kinetic studies for the S. lavendulae ALR suggest that the time-dependent inactivation rate of the enzyme by DCS is absolutely slower than that of the E. coli ALR. We conclude that ALR from DCS-producing S. lavendulae is also one of the self-resistance determinants.

Alanine Racemase↗
PubMed2004

An anatomic study of nasal tip supporting structures.

Successful rhinoplasty depends on nasal tip support and its influence on nasal tip projection. It is generally agreed that the components of nasal tip support include the attachment between the upper and lower lateral cartilages, the attachment between the lateral crus of the lower lateral cartilage and the pyriform aperture, the attachment between the paired domes of the lower lateral cartilages, and the medial crural attachment to the caudal septum. However, these structures are still not clearly determined, and there was no anatomic study of nasal tip supporting structures in Asia. The purpose of this study was to determine the nasal tip supporting structures and find out the differences in these structures between white and Asian people. Ten noses of fresh cadavers were investigated. Dissection was performed and the previously mentioned nasal tip supporting structures were observed and excised. Histologic examination was done with hematoxylin and eosin stain and Van Gieson elastin stain. Macroscopic study showed that there were dense fibrous tissue between the upper and lower lateral cartilages, dense fibrous tissue and sesamoid cartilages between the lateral crus and the pyriform aperture, loose connective tissue between the paired domes of lower lateral cartilages, and no identified specific tissue between the medial crus and the caudal septum. Microscopic investigation allowed a more detailed analysis of these structures. Between the upper and lower lateral cartilages, dense collagen fibers were running in one direction and anchoring firmly to each cartilage, which meets the histologic criteria of a ligament. Between the lateral crus and the pyriform aperture, there were intermingled collagen fibers and muscular fibers, which meets the histologic criteria of fibromuscular tissue. Between the paired domes of lower lateral cartilages, there were few fibers with abundant amorphous ground substances, which meets the histologic criteria of loose connective tissue. Based on our results, we recommend that the previously mentioned nasal tip supporting structures should be named intercartilaginous ligament, sesamoid fibromuscular tissue, and interdomal loose connective tissue, respectively. In addition, we consider that the loose connection between the domes of middle crura and the absence of an attachment of the medial crura to the caudal septum can be one of the reasons why the nasal tip of Asian people is broad and unprojected and the base is wide.

Aged↗
PubMed2003

Adenomyoma of the small intestine: report of two cases and review of the literature.

Adenomyoma of the small intestine is a rare tumor-like lesion composed of exocrine-type ducts and hypertrophic smooth muscle. We describe two cases of adenomyoma of the small intestine. One was an ileal adenomyoma that presented with intussusception occurring in a 7-month-old boy. The other was a jejunal adenomyoma found incidentally in a 63-year-old man with colon cancer. Histologically, the lesions composed of benign ducts and bundles of smooth muscle. The second case was detected on contrast-enhanced computed tomography scan as a small enhancing polypoid mass. We review the previous literature of adenomyoma of the small intestine.

Adenomyoma↗