Identification and characterization of a selenoprotein family containing a diselenide bond in a redox motif
Identification and characterization of a selenoprotein family containing a diselenide bond in a redox motif
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DOI：
10.1073/pnas.0703448104
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发表时间：
2007-08-28
影响因子：
11.1
通讯作者：
Gladyshev, Vadim N.
中科院分区：
文献类型：
--
作者：
Shchedrina, Valentina A.;Novoselov, Sergey V.;Gladyshev, Vadim N.
硒代半胱氨酸（Sec，U）插入蛋白质是由位于称为Sec插入序列（SECIS）元件的茎环结构上游的特定LIGA密码子的翻译编码指导的。硒蛋白是一类在其活性位点上含有一个氧化还原活性Sec的氧化还原酶。在这项工作中，我们确定了一个家庭的硒蛋白，指定SelL，含有两个SEC分开的两个其他残基，形成一个UxxU基序。SelL蛋白显示出不寻常的发生，存在于多种水生生物中，包括鱼类、无脊椎动物和海洋细菌。真核生物和细菌SelL基因都使用单个SECIS元件插入两个Sec。在真核生物中，SECIS位于3'UTR中，而细菌SelL SECIS位于编码区内，并且位于支持插入两个Sec残基中的任一个或这两个残基的距离处。SelL蛋白具有硫氧还蛋白样折叠，其中UxxU基序对应于硫氧还蛋白中的催化CxxC基序，表明SelL蛋白的氧化还原功能。远亲SeIL样蛋白质也被确定在各种生物体中，其中一个或两个Sec被Cys取代。斑马鱼SelL在哺乳动物细胞中瞬时表达，掺入两个Sec并定位于胞质溶胶。在这些细胞中，它以氧化形式发生，不能被DTT还原。在细菌表达系统中，我们直接证明了两个Sec之间形成二硒键，将其确立为天然蛋白质中发现的第一个二硒键。
Selenocysteine (Sec, U) insertion into proteins is directed by translational recoding of specific LIGA codons located upstream of a stem-loop structure known as Sec insertion sequence (SECIS) element. Selenoproteins with known functions are oxidoreductases containing a single redox-active Sec in their active sites. In this work, we identified a family of selenoproteins, designated SelL, containing two Sec separated by two other residues to form a UxxU motif. SelL proteins show an unusual occurrence, being present in diverse aquatic organisms, including fish, invertebrates, and marine bacteria. Both eukaryotic and bacterial SelL genes use single SECIS elements for insertion of two Sec. In eukaryotes, the SECIS is located in the 3' UTR, whereas the bacterial SelL SECIS is within a coding region and positioned at a distance that supports the insertion of either of the two Sec or both of these residues. SelL proteins possess a thioredoxin-like fold wherein the UxxU motif corresponds to the catalytic CxxC motif in thioredoxins, suggesting a redox function of SelL proteins. Distantly related SeIL-like proteins were also identified in a variety of organisms that had either one or both Sec replaced with Cys. Danio rerio SelL, transiently expressed in mammalian cells, incorporated two Sec and localized to the cytosol. In these cells, it occurred in an oxidized form and was not reducible by DTT. In a bacterial expression system, we directly demonstrated the formation of a diselenide bond between the two Sec, establishing it as the first diselenide bond found in a natural protein.