Crystal structure of the radical SAM enzyme catalyzing tricyclic modified base formation in tRNA
Crystal structure of the radical SAM enzyme catalyzing tricyclic modified base formation in tRNA
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DOI：
10.1016/j.jmb.2007.07.024
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发表时间：
2007-10-05
影响因子：
5.6
通讯作者：
Nureki, Osamu
中科院分区：
文献类型：
--
作者：
Suzuki, Yoko;Noma, Akiko;Nureki, Osamu
发现于真核生物和古细菌tRNA中的Wyosine及其衍生物，如Wybutosine，是三环超修饰核苷。在真核生物中，怀布托辛仅存在于tRNA（Phe）的反密码子的37位，在那里它通过在核糖体解码过程中稳定密码子反密码子碱基配对来确保正确的翻译。最近的研究表明，鸟苷生物合成途径包括从鸟苷残基开始的多步酶促反应。在这些步骤中，TYW 1催化第二步，通过环化N-1-甲基鸟苷形成三环结构。在这项研究中，我们解决了TYW 1从詹氏甲烷球菌在2.4 A分辨率的晶体结构。TYW 1假定具有（α/β）（6）拓扑结构的不完整TIM桶，其非常类似于自由基SAM酶的报告结构。因此，TYW 1被认为是通过利用自由基中间体催化环化反应。与其他自由基SAM酶的比较，使我们能够建立一个模型结构与S-腺苷甲硫氨酸和两个[4Fe-4S]簇复合。酵母中的突变分析支持这种复杂模型结构的有效性，其提供了对涉及两个[4Fe-4S]簇以产生复杂三环碱的自由基反应的结构洞察。(c)2007爱思唯尔有限公司保留所有权利。
Wyosine and its derivatives, such as wybutosine, found in eukaryotic and archaeal tRNAs, are tricyclic hypermodified nucleosides. In eukaryotes, wybutosine exists exclusively in position 37, 3'-adjacent to the anticodon, of tRNA(Phe), where it ensures correct translation by stabilizing the codon anticodon base-pairing during the ribosomal decoding process. Recent studies revealed that the wyosine biosynthetic pathway consists of multistep enzymatic reactions starting from a guanosine residue. Among these steps, TYW1 catalyzes the second step to form the tricyclic ring structure, by cyclizing N-1-methylguanosine. In this study, we solved the crystal structure of TYW1 from Methanocaldococcus jannaschii at 2.4 A resolution. TYW1 assumes an incomplete TIM barrel with (alpha/beta)(6) topology, which closely resembles the reported structures of radical SAM enzymes. Hence, TYW1 was considered to catalyze the cyclization reaction by utilizing the radical intermediate. Comparison with other radical SAM enzymes allowed us to build a model structure complexed with S-adenosylmethionine and two [4Fe-4S] clusters. Mutational analyses in yeast supported the validity of this complex model structure, which provides a structural insight into the radical reaction involving two [4Fe-4S] clusters to create a complex tricyclic base. (c) 2007 Elsevier Ltd. All rights reserved.