Biomedical subjects

Sun Yong Lee

Publications and source records attributed to Sun Yong Lee.

3 recordsLinked to original sources

PubMed2006

The C-type Arabidopsis thioredoxin reductase ANTR-C acts as an electron donor to 2-Cys peroxiredoxins in chloroplasts.

2-Cys peroxiredoxins (Prxs) play important roles in the antioxidative defense systems of plant chloroplasts. In order to determine the interaction partner for these proteins in Arabidopsis, we used a yeast two-hybrid screening procedure with a C175S-mutant of Arabidopsis 2-Cys Prx-A as bait. A cDNA encoding an NADPH-dependent thioredoxin reductase (NTR) isotype C was identified and designated ANTR-C. We demonstrated that this protein effected efficient transfer of electrons from NADPH to the 2-Cys Prxs of chloroplasts. Interaction between 2-Cys Prx-A and ANTR-C was confirmed by a pull-down experiment. ANTR-C contained N-terminal TR and C-terminal Trx domains. It exhibited both TR and Trx activities and co-localized with 2-Cys Prx-A in chloroplasts. These results suggest that ANTR-C functions as an electron donor for plastidial 2-Cys Prxs and represents the NADPH-dependent TR/Trx system in chloroplasts.

Arabidopsis↗

PubMed2005

Phosphorylation and concomitant structural changes in human 2-Cys peroxiredoxin isotype I differentially regulate its peroxidase and molecular chaperone functions.

The H2O2-catabolizing peroxidase activity of human peroxiredoxin I (hPrxI) was previously shown to be regulated by phosphorylation of Thr90. Here, we show that hPrxI forms multiple oligomers with distinct secondary structures. HPrxI is a dual function protein, since it can behave either as a peroxidase or as a molecular chaperone. The effects of phosphorylation of hPrxI on its protein structure and dual functions were determined using site-directed mutagenesis, in which the phosphorylation site was substituted with aspartate to mimic the phosphorylated status of the protein (T90D-hPrxI). Phosphorylation of the protein induces significant changes in its protein structure from low molecular weight (MW) protein species to high MW protein complexes as well as its dual functions. In contrast to the wild type (WT)- and T90A-hPrxI, the T90D-hPrxI exhibited a markedly reduced peroxidase activity, but showed about sixfold higher chaperone activity than WT-hPrxI.

Amino Acid Substitution↗

PubMed1978

[Ultrastructural Changes Of The Hepatocytes And Biliary Epithelia Due To Clonorchis Sinensis In Guinea Pigs]

The present study was undertaken to observe the changes of hepatocyte and biliary epithelium in the liver of guinea pigs infected with C. sinensis. Ten guinea pigs infected with 500 metacercariae of C. sinensis each were reared for 11 weeks. After sacrifice, the liver tissues were processed both for conventional light microscopy and for electronmicroscopy. The following results were obtained by light and electronmicroscopic observation of these tissue preparations. 1. The dilatation of bile ducts with chronic inflammatory cell infiltration and fibrosis, and flattening of lining epithelium were observed by light microscopy. Bile duct showed a single low columnar or cuboidal epithelium and subepithelial small round cell infiltration. Papillary proliferation, adenomatous hyperplasia and increase of goblet cells in the subepithelial glands were also noted in some areas of bile ducts. Occasionally, small fibrous nodules in the portal tract replacing bile ducts, surrounded by a heavy infiltrate of small round cells and neutrophils were observed. 2. On light microscopic examination, no cellular damages were seen in the liver cells except mild fatty degeneration. 3. Electronmicroscopic examination of the biliary epithelium revealed increased mucin granules, cytoplasmic projection into lumen, decreased microvilli and obstruction of bile canaliculi. Indistinct and/or irregular appearances of intercellular lateral interdigitation were observed in most of biliary epithelium. 4. On the electronmicrographs of hepatocytes, dilation of endoplasmic reticulum(ER) and destruction of cristae in some mitochondriae were prominent features. Disappearance of cytoplasmic organells and dilatation of bile canaliculi were also monitored. 5. Endothelial cells in the sinusoids were remained intact.

Journal Article↗