The damaging effect of UV-C irradiation on lensα-crystallin

[摘要] Purpose: To evaluate the effect of UV-C irradiation on thestructural properties of α-crystallin and its chaperone activity.Methods: α- and βL-crystallins were isolated from bovinelenses using gel chromatography. The purified α-crystallin wassubjected to UV-C irradiation (254 nm; 1, 2, 5, 10, 20, 50 J/cm2).We measured the tryptophan fluorescence, circular dichroism (CD)spectroscopy in the far UV, and the chaperone activity of bothirradiated and non-irradiated α-crystallin.Results: The tryptophan fluorescence of α-crystallin decreased,whereas the N-formylkynurenine fluorescence increased markedly withincreasing doses of UV-C irradiation. Both the oxidation of Met1and the racemization of Asp151 of αA-crystallin increased ata dose of 1-2 J/cm2 and then gradually decreased. The CD spectrumshowed that the secondary structure of α-crystallin altered withincreasing radiation dose, and almost all of the β-sheet structurewas lost at doses above 50 J/cm2. The chaperone activity ofα-crystallin irradiated with doses under 5 J/cm2 remainedintact. However, it was reduced to only 40% after irradiation at 10J/cm2.Conclusions: Our study suggests that photo-oxidation of tryptophanresidues in α-crystallin may be one of the events that affects thethree-dimensional packing array and chaperone activity of this lensprotein.

[学科分类] 生物化学/生物物理