MiaB蛋白是一种参与tRNA硫醇化和甲基化的双功能自由基S-腺苷甲硫氨酸酶。
MiaB protein is a bifunctional radical-S-adenosylmethionine enzyme involved in thiolation and methylation of tRNA.
作者信息
Pierrel Fabien, Douki Thierry, Fontecave Marc, Atta Mohamed
机构信息
Laboratoire de Chimie et Biochimie des Centres Rédox Biologiques, DRDC-CB, Unité Mixte de Recherche 5047 Commissariat à l'Energie Atomique/CNRS/Université Joseph Fourier, Grenoble, France.
出版信息
J Biol Chem. 2004 Nov 12;279(46):47555-63. doi: 10.1074/jbc.M408562200. Epub 2004 Aug 30.
The last biosynthetic step for 2-methylthio-N(6)-isopentenyl-adenosine (ms(2)i(6)A), present at position 37 in some tRNAs, consists of the methylthiolation of the isopentenyl-adenosine (i(6)A) precursor. In this work we have reconstituted in vitro the conversion of i(6)A to ms(2)i(6)A within a tRNA substrate using the iron-sulfur MiaB protein, S-adenosylmethionine (AdoMet), and a reducing agent. We show that a synthetic i(6)A-containing RNA corresponding to the anticodon stem loop of tRNA(Phe) is also a substrate. This study demonstrates that MiaB protein is a bifunctional system, involved in both thiolation and methylation of i(6)A. In this process, one molecule of AdoMet is converted to 5'-deoxyadenosine, probably through reductive cleavage and intermediate formation ofa5'-deoxyadenosyl radical as observed in other "Radical-AdoMet" enzymes, and a second molecule of AdoMet is used as a methyl donor as shown by labeling experiments. The origin of the sulfur atom is discussed.
2-甲硫基-N⁶-异戊烯基腺苷（ms²i⁶A）存在于某些tRNA的第37位，其最后一步生物合成反应是异戊烯基腺苷（i⁶A）前体的甲硫基化。在这项工作中，我们利用铁硫蛋白MiaB、S-腺苷甲硫氨酸（AdoMet）和一种还原剂，在体外重建了tRNA底物中i⁶A向ms²i⁶A的转化过程。我们发现，一种对应于tRNA（Phe）反密码子茎环的含i⁶A的合成RNA也是该反应的底物。这项研究表明，MiaB蛋白是一个双功能系统，参与i⁶A的硫醇化和甲基化反应。在这个过程中，一分子的AdoMet可能通过还原裂解并形成一个5'-脱氧腺苷自由基中间体（正如在其他“自由基-AdoMet”酶中观察到的那样）转化为5'-脱氧腺苷，标记实验表明，另一分子的AdoMet用作甲基供体。文中还讨论了硫原子的来源。
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