頁籤選單縮合
題 名 | Oxidation-Induced Structural Alterations and its Effect on Chaperone Function of Rat Lens α-Crystallin |
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作 者 | 何愈; 賴建霖; 黃福永; | 書刊名 | Journal of the Chinese Chemical Society |
卷 期 | 45:3 1998.06[民87.06] |
頁 次 | 頁425-431 |
分類號 | 340 |
關鍵詞 | α-crystallin; Chaperone; Circular dichroism; Oxidation; |
語 文 | 英文(English) |
英文摘要 | An ascorbate-FeCl□-EDTA-H□O□ system was used to oxidize rat lens α-crystallins. Under this oxidative insult, the chaperone activity of α-crystallin toward γ-crystallin was shown to decrease significantly, which is quite different from the result reported by Wang and Spector. (Invest. Ophthalmol. Vis. Sci. 1995, 36, 311 321.) Fluorescence spectroscopy and circular dichroism were employed to characterize the structura changes of oxidized α-crystallin. It was found that fluorescence intensity of 1-anilinonaphthalene-8-sulphonate (ANS) bound to oxidized α-crystallin increased comparing to that bound to normal α-crystallin suggesting oxidation causes the exposure of more hydrophobic regions. Further, α-crystallin's fluorescence intensity in response to tryptophan residues showed a pseudo first order decline. Amino acid analysis of normal versus oxidized α-crystallin confirmed actual decline in tryptophan levels, showing about 80% of tryptophan being modified after 10-hour oxidation. Circular dichroism showed both changes in the secondary and tertiary structures of oxidized α-crystallin, characterized by a large loss of aromatic- type amino acid interactions and a large loss of β-sheet structure. In conclusion, modified tryptophan, secondary and tertiary structural changes of α-crystallin correlate best with the reduction of chaperone function, the curves all showing a linear slope for 10 hours, then plateauing. These results indicate that the decrease of α-crystallin chaperone activity is attributed to the structural changes. |
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