Age-Dependent Deamidation of Lifelong Proteins in the Human Lens
Age-Dependent Deamidation of Lifelong Proteins in the Human Lens
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DOI：
10.1167/iovs.09-4308
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发表时间：
2010-06-01
影响因子：
4.4
通讯作者：
Truscott, Roger J. W.
中科院分区：
文献类型：
--
作者：
Hains, Peter G.;Truscott, Roger J. W.
目的.脱酰胺是人类透镜蛋白中常见的翻译后修饰，并且可能是这种终身蛋白质的年龄相关变性的关键因素。本研究的目的是确定旧镜片中脱酰胺的位点。胰蛋白酶的高效液相色谱/质谱法用于鉴定主要人透镜晶体蛋白中的脱酰胺位点。将年龄较大的正常和年龄匹配的白内障晶状体与胎儿晶状体进行比较。在旧晶状体中，脱酰胺的谷氨酰胺和天冬酰胺残基数量大致相等;然而，Asn的脱酰胺程度是Gln的3倍（Asn，22.6% +/- 3.6%; Gln，6.6% +/- 1.3%）。单个晶体蛋白的脱酰胺程度明显不同，脱酰胺残基通常位于多肽的离散区域内。大百分比（42%）的脱酰胺位点的特征在于从原始Gln或Asn中去除一个残基的碱性氨基酸的存在。在9个这样的网站，Asn脱酰胺的程度平均为50%，在老化的镜头。老年正常晶状体和核性白内障晶状体的晶状体蛋白脱酰胺作用差异不大。相同数量的Asn和Gln残基在来自老化的正常晶状体和白内障晶状体的晶状体蛋白中脱酰胺。在终身蛋白质中，如在透镜中的那些蛋白质中，Asn/Gln的脱酰胺化可能在很大程度上受碱催化过程的控制。（Invest Ophthalmol维斯科学。2010;51：3107-3114）DOI：10.1167/iovs.09-4308
PURPOSE. Deamidation is a common posttranslational modification in human lens crystallins and may be a key factor in the age-related denaturation of such lifelong proteins. The aim of this study was to identify the sites of deamidation in older lenses.METHODS. High-performance liquid chromatography/mass spectrometry of tryptic digests was used to identify sites of deamidation in the major human lens crystallins. Older normal and age-matched cataractous lenses were compared with fetal lenses.RESULTS. Approximately equal numbers of glutamine and asparagine residues were deamidated in older lenses; however, the extent of deamidation of Asn was three times greater than that of Gln (Asn, 22.6% +/- 3.6%; Gln, 6.6% +/- 1.3%). Individual crystallins differed markedly in their extent of deamidation, and deamidated residues were typically localized within discrete regions of the polypeptides. A large percentage (42%) of the sites of deamidation were characterized by the presence of a basic amino acid one residue removed from the original Gln or Asn. At nine such sites, the extent of Asn deamidation averaged 50% in aged lenses. There were few differences in deamidation between crystallins of aged normal and nuclear cataractous lenses.CONCLUSIONS. Equal numbers of Asn and Gln residues are deamidated in crystallins from aged normal and cataractous lenses. Deamidation of Asn/Gln in lifelong proteins, such as those in the lens, may be governed to a significant degree by base-catalyzed processes. (Invest Ophthalmol Vis Sci. 2010;51:3107-3114) DOI: 10.1167/iovs.09-4308