The radical SAM enzyme AlbA catalyzes thioether bond formation in subtilosin A
The radical SAM enzyme AlbA catalyzes thioether bond formation in subtilosin A
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DOI：
10.1038/nchembio.798
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发表时间：
2012-04-01
影响因子：
14.8
通讯作者：
Marahiel, Mohamed A.
中科院分区：
文献类型：
--
作者：
Fluehe, Eif;Knappe, Thomas A.;Marahiel, Mohamed A.
Subtilosin A 是一种由 35 个残基组成的核糖体合成细菌素，由枯草芽孢杆菌的 sbo-alb 操纵子编码。它由头尾相连的环状肽主链组成，该主链还受到三个半胱氨酸分别与一个苏氨酸和两个苯丙氨酸的 α-碳之间的三个不寻常的硫醚键的限制。在这项研究中，我们证明这些键是由自由基 S-腺苷甲硫氨酸酶 AlbA 合成的，该酶由 sbo-alb 操纵子编码，包含两个 [4Fe-4S] 簇。一个 [4Fe-4S] 簇由原型 CXXXCXXC 基序协调，负责观察到的 S-腺苷甲硫氨酸裂解反应，而第二个 [4Fe-4S] 簇是生成所有三个硫醚键所必需的。在所获得的结果的基础上，我们提出了一种新的硫醚键形成的自由基机制。此外，我们发现 AlbA 引导的底物转化是前导肽依赖性的，这表明硫醚键的形成是枯草溶菌素 A 成熟过程中的第一步。
Subtilosin A is a 35-residue, ribosomally synthesized bacteriocin encoded by the sbo-alb operon of Bacillus subtilis. It is composed of a head-to-tail circular peptide backbone that is additionally restrained by three unusual thioether bonds between three cysteines and the alpha-carbon of one threonine and two phenylalanines, respectively. In this study, we demonstrate that these bonds are synthesized by the radical S-adenosylmethionine enzyme AlbA, which is encoded by the sbo-alb operon and comprises two [4Fe-4S] clusters. One [4Fe-4S] cluster is coordinated by the prototypical CXXXCXXC motif and is responsible for the observed S-adenosylmethionine cleavage reaction, whereas the second [4Fe-4S] cluster is required for the generation of all three thioether linkages. On the basis of the obtained results, we propose a new radical mechanism for thioether bond formation. In addition, we show that AlbA-directed substrate transformation is leader-peptide dependent, suggesting that thioether bond formation is the first step during subtilosin A maturation.