期刊
BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR BASIS OF DISEASE
卷 1782, 期 1, 页码 22-34出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.bbadis.2007.10.003
关键词
ascorbic acid; glycation; lens proteins; protein aggregation; light scattering
资金
- NATIONAL EYE INSTITUTE [R01EY002035, R24EY014795] Funding Source: NIH RePORTER
- NEI NIH HHS [R01 EY002035, R24 EY014795, R01 EY002035-30, EY 014795, EY02035] Funding Source: Medline
Previous studies from this laboratory have shown that there are striking similarities between the yellow chromophores, fluorophores and modified amino acids released by proteolytic digestion from calf lens proteins ascorbylated in vitro and their counterparts isolated from aged and cataractous lens proteins. The studies reported in this communication were conducted to further investigate whether ascorbic acid-mediated modification of lens proteins could lead to the formation of lens protein aggregates capable of scattering visible light, similar to the high molecular aggregates found in aged human tenses. Ascorbic acid, but not glucose, fructose, ribose or erythrulose, caused the aggregation of calf lens proteins to proteins ranging from 2.2 x 10(6) up to 3.0 x 10(8) Da. This compared to proteins ranging from 1.8 x 10(6) up to 3.6 x 10(8) Da for the water-soluble (WS) proteins isolated from aged human lenses. This aggregation was likely due to the glycation of lens crystallins because [U-C-14] ascorbate was incorporated into the aggregate fraction and because NaCNBH3, which reduces the initial Schiff base, prevented any protein aggregation. Reactions of ascorbate with purified crystallin fractions showed little or no aggregation of a-crystallin, significant aggregation of beta(H)-crystallin, but rapid precipitation of purified beta(L)- and gamma-crystallin. The aggregation of lens proteins can be prevented by the binding of damaged crystallins to alpha-crystallin due to its chaperone activity. Depending upon the ratios between the components of the incubation mixtures, a-crystallin prevented the precipitation of the purified beta(L)- and gamma-crystallin fractions during ascorbylation. The addition of at least 20% of alpha-crystallin by weight into glycation mixtures with beta(L)-, or gamma-crystallins completely inhibited protein precipitation, and increased the amount of the high molecular weight aggregates in solution. Static and dynamic light scattering measurements of the supernatants from the ascorbic acid-modified mixtures of alpha- and beta(L)-, or gamma-crystallins showed similar molar masses (up to 10(8) Da) and hydrodynamic diameter (up to 80 nm). These data support the hypothesis, that if the lens reducing environment is compromised, the ascorbylation of lens crystallins can significantly change the short range interactions between different classes of crystallins leading to protein aggregation, light scattering and eventually to senile cataract formation. (C) 2007 Elsevier B.V. All rights reserved.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据