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Characteristics of Cytosolic Calcium-Independent Phospholipase A2 Isolated from Rat Liver
(Jong Hak Won),(Doe Sun Na),(Hae Jin Rhee),(Young Min Park) 생화학분자생물학회 1999 BMB Reports Vol.32 No.2
A calcium-independent phospholipase A₂ (iPLA₂) was identified from the cytosolic fraction of rat liver cells. On gel filtration chromatography, the iPLA₂ activity was eluted as broad peaks of 150 to 500 kDa. The enzyme was maximally active at pH 7.5, retained 75% of its original activity after heating at 50℃ for 5 h, and was inhibited by Ca^(2+), Mg^(2+), and Zn^(2+) ions, but was not affected by Na+ and K+ ions. The enzymatic activity was increased up to 150% by 1 to 4 mM DTT and was inhibited up to 25% by 0.1 to 1 mM PMSF. The iPLA₂ activity had preference for the head group of phospholipass, where phosphatidylethanolamine was preferred to phosphatidylcholine. The results suggest that the iPLA₂ may be a novel enzyme distinct from the previously reported iPLA₂s.
Characteristics of Cytosolic Calcium-Independent Phospholipase A₂ Isolated from Rat Liver
Park, Young Min,Na, Doe Sun,Won, Jong Hak,Rhee, Hae Jin The Korea Science and Technology Center 1999 BMB Reports Vol.32 No.2
A calcium-independent phospholipase A₂(iPLA₂)was identified from the cytosolic fraction of rat liver cells. On gel filtration chromatography, the iPLA₂activity was eluted as broad peaks of 150 to 500 kDa. The enzyme was maximally active at pH 7.5, retained 75% of its original activity after heating at 50。C for 5 h, and was inhibited by Ca²+, Mg²+, and Zn²+ ions, but was not affected by Na+ and K+ ions. The enzymatic activity was increased up to 150% by 1 to 4 mM DTT and was inhibited up to 25% by 0.1 to 1 mM PMSF. The iPLA₂activity had preference for the head group of phospholipids, where phosphatidylethanolamine was preferred to phosphatidycholine. The results suggest that the iPLA₂may be a novel enzyme distinct from the previously reported iPLA₂s.
Translocation of Annexin I to the Nucleus by Epidermal Growth Factor in A549 Cells
Na, Doe Sun,Lee, Soo Ok,Kim, Seung Wook,Rhee, Hae Jin,Park, Young Min The Korea Science and Technology Center 1999 BMB Reports Vol.32 No.1
Annexin 1 (also called lipocortin 1), a 37-kDa member of the annexin family of proteins, has been implicated in the mitogenic signal transduction by epidermal growth factor (EGF). Annexin 1 is phosphorylated by the EGF signal, however, the role of annexin 1 in the EGF signal transduction is still unknown. To transduce extracellular signals into the intracellular targets, selective translocation of the signaling molecules to their targets would be necessary. In this study, we examined the subcellular locations of annexin 1 during EGF signal transduction. Treatment of A549 cells with EGF resulted in the translocation of cytoplasmic annexin 1 to the nucleus and perinuclear region as determined by Western blot and immunofluorescent staining. The nuclear translocation of annexin 1 was inhibited by tyrphostin AG 1478 and genistein, the inhibitors of EGF receptor kinase and downstream tyrosine kinases, respectively. Pretreatment of cells with cyclohexamide did not inhibit the nuclear translocation. The results suggest that nuclear translocation of annexin 1 is controlled by a series of kinase dependentevents in the EGF receptor signaling pathway and may be important in tranducing the signals by EGF.
Improvement of the Expression Level of Human Lipocortin Gene in E . coli
Na, Doe Sun,Song, In Sung,Huh, Kwahng Rae,Lee, Hay Young 한국유전학회 1989 Genes & Genomics Vol.11 No.4
Lipocortins are a family of proteins with phospholipase A2 inhibitory activities. Inhibition of phospholipase A2 in the cell is believed to inhibit the production of arachidonic acie which is a precursor of prostaglandins and leukotrienes, the mediators of inflammation. Overproduction of recombinant lipocortin-I would facilitate the studies on the in vivo action of this protein. We have produced recombinant lipocortin-I previously. Plasmid pHT1 harboring the lipocortin-I gene under the control of the trc promoter was utilized to produce lipocortin-I in E. coli. The level of lipocortin-I expression was about 2% of the total E. coli proteins. To improve the expression level, few changes were made on plasmid pHT1 to yield pHT2. The expression level of lipocortin using pHT2 was around 8-10% of the total E. coli proteins. Details will be discussed.
ATP and GTP Hydrolytic Function of N-terminally Deleted Annexin I
Na, Doe Sun,Hyun, Young-Lan,Park, Young Min The Korea Science and Technology Center 2000 BMB Reports Vol.33 No.4
Annexin I is a 37 kDa member of the annexin family of calcium-dependent phospholipid binding proteins. Annexin I plays regulatory roles in various cellular processes including cell proliferation and differentiation. Recently we found that annexin I is a heat shock protein (HSP) and displays a chaperone-like function. In this paper we investigated the function of annexin I as an ATPase using 1 to 32 amino acids deleted annexin I(△-annexin I). △-Annexin I hydrolyzed ATP as determined by thin layer chromatography. The ability of ATP hydrolysis was inhibited by ADP, GTP and GDP, but not by the AMP, GMP and cAMP. In view of the ATP hydrolyzing function of HSP, the results support the function of annexin I as a HSP.