AIM: To explore whether carnosine can protect α -crys-tallin modification and decreased chaperone by a steroid,and whether carnosine could directly react with a steroid.METHODS: Bovine lens α L-crystallin was separated by size-exclusion chromatography on a Sephacyl S-300 HR column. α L-Crystallin was incubated with different concentrations of prednisolone-21-hemisuccinate (P-21-H)with or without carnosine for different times. The chaperone activity of α L-crystallin was monitored using the prevention thermal aggregation of α L-crystallin. The modified α L-crystallinwas examined by SDS-PAGE and fluorescence measurements. The absorbance spectra of solutions of carnosine and P-21-H were investigated.RESULTS: P-21-H decreased the chaperone activity ofα L-crystallin in a concentration- and time-dependent fashion. Carnosine only worsened this effect. The tryptophan fluorescence intensity of α L-crystallin modified by P-21-H was significantly decreased compared to unmodified crystallin, whereas its non-tryptophan fluorescence was increased with a shift to longer wavelengths in a time- and dose-dependent manner, suggesting that new fluorophores are possibly formed. Carnosine readily reacted with P-21-H thereby inhibiting steroid-mediated protein modification as revealed electrophoretically. The increased absorbance was time-dependent, suggesting adducts may be formed between carnosine and P-21-H.CONCLUSION: Carnosine reacts with P-21-H, which suggests carnosine's potential as a possible anti-seroid agent.%目的:研究肌肽对糖皮质激素诱导的α-晶状体蛋白修饰和分子伴侣功能降低的保护作用,以及肌肽与糖皮质激素的直接反应.方法:采用SephacrylS-300HR凝胶柱分离牛αL-晶状体蛋白.αL-晶状体蛋白分别与不同浓度的泼尼松龙-21-半琥珀酸(P-21-H)及肌肽孵育不同时间.以αL-晶状体蛋白对热凝聚的抑制作为分子伴侣活性指标.采用SDS-聚丙烯酰胺凝胶电泳和荧光光度仪来监测被修饰的αL-晶状体蛋白,并观察肌肽和泼尼松龙-21-半琥珀酸作用后的光谱变化.结果:泼尼松龙-21-半琥珀酸可导致浓度和时间依赖性αL-晶状体蛋白分子伴侣活性的降低,但是肌肽加剧了这种效应.被泼尼松龙-21-半琥珀酸修饰后的较未被修饰的αL-晶状体蛋白色氨酸荧光强度显著降低,但是其非色氨酸荧光强度向较长波长移位,并呈现时间-剂量依赖的增强,提示有新的荧光色素物的形成.SDS-聚丙烯酰胺凝胶电泳结果显示肌肽能与泼尼松龙-21-半琥珀酸迅速反应,从而抑制激素诱导的蛋白质修饰.时间依赖性的光吸收强度增加提示肌肽与泼尼松龙-21-半琥珀酸反应可能形成了新的加合物.结论:肌肽能够与泼尼松龙-21-半琥珀酸直接反应,肌肽具有潜在的抗糖皮质激素作用.
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