HYDROXYL RADICAL MEDIATED DAMAGE TO PROTEINS, WITH SPECIAL REFERENCE TO THE CRYSTALLINS
HYDROXYL RADICAL MEDIATED DAMAGE TO PROTEINS, WITH SPECIAL REFERENCE TO THE CRYSTALLINS
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DOI：
10.1021/bi00132a021
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发表时间：
1992-05-05
期刊：
影响因子：
2.9
通讯作者：
SAITO, I
中科院分区：
文献类型：
--
作者：
GUPTASARMA, P;BALASUBRAMANIAN, D;SAITO, I
已知眼透镜蛋白（晶状体蛋白）的氧化修饰引起蛋白质交联和聚集，其导致透镜混浊或白内障。在此，我们将注意力集中在晶状体蛋白和某些“对照”蛋白与羟基自由基（.OH）反应后发生的氧化损伤上，羟基自由基在透镜中由光敏化或芬顿反应产生。在本研究中，我们已经合成并使用双氢过氧化物I作为“光芬顿”试剂，以光解产生纯.OH，不含其他氧自由基。我们的研究结果如下：（i）色氨酸残基被.OH氧化为N-甲酰犬尿氨酸和相关化合物，但这本身不会导致蛋白质的共价聚集。(ii)Tyr残基与.OH反应，但显然不产生二羟基苯丙氨酸或酪氨酸。蛋白质交联也不会因此发生。(iii)His残基的氧化似乎是蛋白质交联所必需的。不含组氨酸的蛋白质在与. OH反应时不形成高分子量产物。通过在其他蛋白质中形成加合物来保护His残基抑制交联。(iv)赖氨酸残基似乎参与交联反应。通过蛋白质的马来酰化保护Lys残基抑制交联。(v)氧化的蛋白质在性质上比母体更酸性，并且它可能改变了构象特征。
Oxidative modification of the eye lens proteins, the crystallins, is known to cause protein cross-links and aggregates which lead to lens opacification or cataracts. We focus attention here on oxidative damage occurring in crystallins and some "control" proteins upon reaction with the hydroxyl radical (.OH) which, in the lens, is generated by photosensitization or by the Fenton reaction. In the present study, we have synthesized and used the bishydroperoxide I as a "photo-Fenton" reagent, in order to photolytically generate pure .OH, free of other oxyradicals. Our findings are the following: (i) Trp residues are oxidized by .OH to N-formylkynurenine and related compounds, but this in itself does not lead to covalent aggregation of the protein. (ii) Tyr residues react with .OH, but apparently do not produce dihydroxyphenylalanine or bityrosine. Nor do protein cross-links occur as a result. (iii) Oxidation of His residues appears to be obligatory for protein cross-linking. Histidine-free proteins do not form high molecular weight products upon reaction with .OH. Protection of His residues by adduct formation in other proteins inhibits cross-linking. (iv) Lys residues seem to participate in the cross-linking reaction. Protection of the Lys residues by maleylation of the protein inhibits cross-linking. (v) The oxidized protein is more acidic in nature than the parent, and it might have altered conformational features.