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首页> 外文期刊>Biochemistry >Mechanism of the Very Efficient Quenching of Tryptophan Fluorescence in Human γD- and γS-Crystallins: The γ-Crystallin Fold May Have Evolved To Protect Tryptophan Residues from Ultraviolet Photodamage
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Mechanism of the Very Efficient Quenching of Tryptophan Fluorescence in Human γD- and γS-Crystallins: The γ-Crystallin Fold May Have Evolved To Protect Tryptophan Residues from Ultraviolet Photodamage

机译：人γD和γS-结晶蛋白中色氨酸荧光的高效猝灭机理：γ-结晶蛋白折叠可能已经进化为保护色氨酸残基免受紫外线的光损伤。

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摘要

Proteins exposed to UV radiation are subject to irreversible photodamage through covalentnmodification of tryptophans (Trps) and other UV-absorbing amino acids. Crystallins, the major proteinncomponents of the vertebrate eye lens that maintain lens transparency, are exposed to ambient UV radiationnthroughout life. The duplicated u0002-sheet Greek key domains of u0002- and γ-crystallins in humans and allnother vertebrates each have two conserved buried Trps. Experiments and computation showed that thenfluorescence of these Trps in human γD-crystallin is very efficiently quenched in the native state bynelectrostatically enabled electron transfer to a backbone amide [Chen et al. (2006) Biochemistry 45,n11552-11563]. This dispersal of the excited state energy would be expected to minimize protein damagenfrom covalent scission of the excited Trp ring. We report here both experiments and computation showingnthat the same fast electron transfer mechanism is operating in a different crystallin, human γS-crystallin.nExamination of solved structures of other crystallins reveals that the Trp conformation, as well as favorablynoriented bound waters, and the proximity of the backbone carbonyl oxygen of the n - 3 residues beforenthe quenched Trps (residue n), are conserved in most crystallins. These results indicate that fast chargentransfer quenching is an evolved property of this protein fold, probably protecting it from UV-inducednphotodamage. This UV resistance may have contributed to the selection of the Greek key fold as thenmajor lens protein in all vertebrates.
机译：暴露于紫外线辐射的蛋白质会通过色氨酸（Trps）和其他吸收紫外线的氨基酸的共价修饰而遭受不可逆的光损伤。晶状体蛋白（脊椎动物晶状体的主要蛋白成分，可保持晶状体透明性）在整个生命过程中都暴露于环境紫外线辐射下。在人类和所有其他脊椎动物中，u0002-和γ-晶状蛋白的重复的u0002-sheet希腊语关键域分别具有两个保守的埋藏色氨酸。实验和计算表明，通过静电使电子转移到主链酰胺上，天然γ-晶状体蛋白中的这些Trps的荧光可以非常有效地在天然状态下猝灭[Chen等。 （2006）Biochemistry 45，n11552-11563]。激发态能量的这种分散将被期望最小化由激发的Trp环的共价断裂引起的蛋白质损伤。我们在此报告的实验和计算均表明，相同的快速电子传递机制在不同的晶状蛋白人类γS-晶状蛋白中起作用.n对其他晶状蛋白的溶解结构的检查表明，Trp构象以及有利的n取向束缚水以及在大多数结晶蛋白中，被淬灭的Trps（残基n）之前的n-3个残基的骨架羰基氧是保守的。这些结果表明快速的电荷转移猝灭是该蛋白折叠的进化性质，可能使其免受紫外线诱导的光损伤。这种抗紫外线性可能有助于选择希腊关键折叠作为所有脊椎动物中的主要晶状体蛋白。

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  • 来源
    《Biochemistry》 |2009年第17期|p.3708-3716|共9页
  • 作者

    Jiejin Chen Patrik R. Callis and Jonathan King;

  • 作者单位

    Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and Department of Chemistryand Biochemistry, Montana State UniVersity, Bozeman, Montana 59717;

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