Acetylation of αA-crystallin in the human lens: Effects on structure and chaperone function
Acetylation of αA-crystallin in the human lens: Effects on structure and chaperone function
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DOI：
10.1016/j.bbadis.2011.11.011
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发表时间：
2012-02-01
影响因子：
6.2
通讯作者：
Biswas, Ashis
中科院分区：
文献类型：
--
作者：
Nagaraj, Ram H.;Nahomi, Rooban B.;Biswas, Ashis
晶体蛋白是人体晶状体中的一种主要蛋白，通过其伴侣蛋白的功能帮助维持晶状体的透明度。在这项研究中，我们证明了许多晶状体蛋白包括α - a -晶体蛋白在体内被乙酰化。我们发现α -晶体蛋白中的K70和K99， α -晶体蛋白中的K92和K166在人晶状体中乙酰化。为了确定乙酰化对伴侣蛋白功能和结构变化的影响，我们用乙酸酐对α - a -晶体蛋白进行了乙酰化。所得蛋白对N-epsilon-acetyllysine抗体表现出较强的免疫反应性，这与乙酰化程度直接相关。与未修饰的蛋白相比，体外乙酰化α - a -晶体蛋白对四种不同客户蛋白中的三种具有更高的伴侣功能。由于α - a -晶体蛋白中的赖氨酸（残基70；K70）在体内被乙酰化，我们用乙酰化模拟物生成了一个蛋白质，用谷氨酰胺（K70Q）代替Lys70。与Wt蛋白相比，K70Q突变蛋白对三种客户蛋白的伴侣蛋白功能增强，但对γ -结晶蛋白的伴侣蛋白功能降低。乙酰化蛋白表现出更高的表面疏水性和色氨酸荧光，改变了二级和三级结构，热力学稳定性下降。总之，我们的数据表明，α - a -晶体蛋白的乙酰化发生在人类晶状体中，并影响蛋白质的伴侣功能。(C) 2011 Elsevier B.V.版权所有
alpha-Crystallin is a major protein in the human lens that is perceived to help to maintain the transparency of the lens through its chaperone function. In this study, we demonstrate that many lens proteins including alpha A-crystallin are acetylated in vivo. We found that K70 and K99 in alpha A-crystallin and, K92 and K166 in alpha B-crystallin are acetylated in the human lens. To determine the effect of acetylation on the chaperone function and structural changes, alpha A-crystallin was acetylated using acetic anhydride. The resulting protein showed strong immunoreactivity against a N-epsilon-acetyllysine antibody, which was directly related to the degree of acetylation. When compared to the unmodified protein, the chaperone function of the in vitro acetylated alpha A-crystallin was higher against three of the four different client proteins tested. Because a lysine (residue 70; K70) in alpha A-crystallin is acetylated in vivo, we generated a protein with an acetylation mimic, replacing Lys70 with glutamine (K70Q). The K70Q mutant protein showed increased chaperone function against three client proteins compared to the Wt protein but decreased chaperone function against gamma-crystallin. The acetylated protein displayed higher surface hydrophobicity and tryptophan fluorescence, had altered secondary and tertiary structures and displayed decreased thermodynamic stability. Together, our data suggest that acetylation of alpha A-crystallin occurs in the human lens and that it affects the chaperone function of the protein. (C) 2011 Elsevier B.V. All rights reserved.