Photo-induced peptide cleavage in the green-to-red conversion of a fluorescent protein
Photo-induced peptide cleavage in the green-to-red conversion of a fluorescent protein
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DOI：
10.1016/s1097-2765(03)00393-9
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发表时间：
2003-10-01
期刊：
影响因子：
16
通讯作者：
Miyawakil, A
中科院分区：
文献类型：
--
作者：
Mizuno, H;Mal, TK;Miyawakil, A
水母（Aequorea GFP）的绿色荧光蛋白和珊瑚物种的GFP样蛋白在其蛋白质序列中编码光吸收发色团。珊瑚荧光蛋白Kaede含有一种三肽，His（62）-Tyr（63）-Gly（64），它作为一种绿色发色团，可被光转化为红色。在这里，我们提出了绿色到红色的光转换的结构基础。如在水母GFP中，源自三肽的发色团4-（对羟基亚苄基）-5-咪唑啉酮介导Kaede中的绿色荧光。紫外线照射通过正式的β-消除反应在Kaede蛋白质内酰胺氮和His（62）处的α碳（Calpha）之间引起非常规裂解，这需要完整的蛋白质用于其催化。随后在His（62）-Calpha和-C β之间形成双键，将π-共轭延伸到His（62）的咪唑环，产生新的还原发色团2-[（1 E）-2-（5-咪唑基）乙烯基]4-（对羟基苯亚甲基）-5-咪唑啉酮。本研究不仅揭示了荧光蛋白化学结构的多样性，而且为翻译后修饰机制增加了一个新的维度。
Green fluorescent protein from the jellyfish (Aequorea GFP) and GFP-like proteins from coral species encode light-absorbing chromophores within their protein sequences. A coral fluorescent protein, Kaede, contains a tripeptide, His(62)-Tyr(63)-Gly(64), which acts as a green chromophore that is photoconverted to red. Here, we present the structural basis for the green-to-red photoconversion. As in Aequorea GFP, a chromophore, 4-(p-hydroxybenzylidene)-5-imidazolinone, derived from the tripeptide mediates green fluorescence in Kaede. UV irradiation causes an unconventional cleavage within Kaede protein between the amide nitrogen and the alpha carbon (Calpha) at His(62) via a formal beta-elimination reaction, which requires the whole, intact protein for its catalysis. The subsequent formation of a double bond between His(62)-Calpha and -Cbeta extends the pi-conjugation to the imidazole ring of His(62), creating a new redemitting chromophore, 2-[(1E)-2-(5-imidazolyl)ethenyl]4-(p-hydroxybenzylidene)-5-imidazolinone. The present study not only reveals diversity in the chemical structure of fluorescent proteins but also adds a new dimension to posttranslational modification mechanisms.