Biomedical subjects

Eun Hee Cho

Publications and source records attributed to Eun Hee Cho.

5 recordsLinked to original sources

PubMed2003

A novel flavin-containing monooxygenase from Methylophaga sp strain SK1 and its indigo synthesis in Escherichia coli.

We cloned a gene from Methylophaga sp. strain SK1. This gene was responsible for producing, the blue pigment, indigo. The complete open reading frame was 1371 bp long, which encodes a protein of 456 amino acids. The molecular mass of the encoded protein was 105 kDa, consisting of homodimer of 54 kDa with an isoelectric point of 5.14. The deduced amino acid sequence from the gene showed approximately 30% identities with flavin-containing monooxygenases (FMOs) of human (FMO1-FMO5), Arabidopsis, and yeast. It contained three characteristic sequence motifs of FMOs: FAD binding domain, FMO-identifying sequence motif, and NADPH binding domain. In addition, the biochemical properties such as substrate specificities and absorption spectra were similar to the eukaryotic FMO families. Thus, we assigned the enzyme to be a bacterial FMO. The recombinant Escherichia coli expressing the bacterial FMO produced up to 160 mg of indigo per liter in the tryptophan medium after 12h cultivation. This suggests that the recombinant strain has a potential to be applied in microbial indigo production.

Amino Acid Motifs↗

PubMed2002

Importance of glutamate 279 for the coenzyme binding of human glutamate dehydrogenase.

Although the structure of glutamate dehydrogenase (GDH) has been reported from various sources including mammalian GDH, there are conflicting views regarding the location and mechanism of actions of the coenzyme binding. We have expanded these speculations by photoaffinity labeling and cassette mutagenesis. Photoaffinity labeling with a specific probe, [(32)P]nicotinamide 2-azidoadenosine dinucleotide, was used to identify the NAD(+) binding site within human GDH encoded by the synthetic human GDH gene and expressed in Escherichia coli as a soluble protein. Photolabel-containing peptides generated with trypsin were isolated by immobilized boronate affinity chromatography. Photolabeling of these peptides was most effectively prevented by the presence of NAD(+) during photolysis, demonstrating a selectivity of the photoprobe for the NAD(+) binding site. Amino acid sequencing and compositional analysis identified Glu(279) as the site of photoinsertion into human GDH, suggesting that Glu(279) is located at or near the NAD(+) binding site. The importance of the Glu(279) residue in the binding of NAD(+) was further examined by cassette mutagenesis with mutant enzymes containing Arg, Gly, Leu, Met, or Tyr at position 279. The mutagenesis at Glu(279) has no effects on the expression or stability of the different mutants. The K(m) values for NAD(+) were 10-14-fold greater for the mutant GDHs than for wild-type GDH, whereas the V(max) values were similar for wild-type and mutant GDHs. The efficiency (k(cat)/K(m)) of the mutant GDH was reduced up to 18-fold. The decreased efficiency of the mutants results from the increase in K(m) values for NAD(+). In contrast to the K(m) values for NAD(+), wild-type and mutant GDHs show similar K(m) values for glutamate, indicating that substitution at position 279 had no appreciable effect on the affinity of enzyme for glutamate. There were no differences in sensitivities to ADP activation and GTP inhibition between wild-type and mutant GDH, suggesting that Glu(279) is not directly involved in allosteric regulation. The results with photoaffinity labeling and cassette mutagenesis studies suggest that Glu(279) plays an important role for efficient binding of NAD(+) to human GDH.

Adenosine Diphosphate↗

PubMed2002

Interactions between integrase and excisionase in the phage lambda excisive nucleoprotein complex.

Bacteriophage lambda site-specific recombination comprises two overall reactions, integration into and excision from the host chromosome. Lambda integrase (Int) carries out both reactions. During excision, excisionase (Xis) helps Int to bind DNA and introduces a bend in the DNA that facilitates formation of the proper excisive nucleoprotein complex. The carboxyl-terminal alpha-helix of Xis is thought to interact with Int through direct protein-protein interactions. In this study, we used gel mobility shift assays to show that the amino-terminal domain of Int maintained cooperative interactions with Xis. This finding indicates that the amino-terminal arm-type DNA binding domain of Int interacts with Xis.

Bacteriophage lambda↗

PubMed2002

Dipolarity, hydrogen-bond basicity and hydrogen-bond acidity of aqueous poly(ethylene glycol) solutions.

Poly(ethylene glycol) (PEG) in water is known to alter the structure and/or state of water to give a different polarity from that of pure water. We determined using the solvatochromic comparison method the dipolarity/polarizability (pi*), hydrogen bond (HB) accepting basicity (beta) and HB donating acidity (alpha) of aqueous solutions of PEGs of variegated molecular weights at different concentrations in order to understand the influence of the polymer on these properties of water. It was observed that PEG decreases alpha for water while it does not change pi* and beta appreciably in the range of the molecular weight and compositions studied.

Hydrogen Bonding↗

PubMed2002

The comparison between Behçet's disease and spondyloarthritides: does Behçet's disease belong to the spondyloarthropathy complex?

This study was to clarify whether Behcet's disease (BD) could be classified into the spondyloarthropathy (SpA) complex. It was undertaken on 58 patients with BD (BD group), 56 patients with SpA (SpA group), and 3 patients who concurrently satisfied the criteria for BD and SpA (BDSpA group). The clinical parameters and known susceptible HLA antigens were compared between BD group and SpA group. In addition, 3 patients in BDSpA group were reviewed. The prevalence of definitive sacroiliitis (SI) in BD group and SpA group was 46.4% and 5.2%, respectively. However, none had a definitive SI in healthy controls. Enthesitis was observed in 3.4% of BD group and in 50% of SpA group. The patterns of eye involvement were different between these two groups. HLA-B27 was negative in all 49 patients of BD group, whereas it was positive in 67.9% of SpA group. The prevalence of HLA-B51 was 51.7% in BD group, and that in SpA group was 21.4%. One patient in BDSpA group was considered to have concurrent BD and ankylosing spondylitis (AS). Another patient was closer to AS, and the third to BD. Conclusively, it seems that BD could not be classified into the SpA complex.

Adult↗