Department of Chemistry/Biochemistry, Philipps-Universität Marburg, Hans-Meerwein Straße 4, D-35043 Marburg, Germany.
J Am Chem Soc. 2013 Jan 23;135(3):959-62. doi: 10.1021/ja310542g. Epub 2013 Jan 9.
The sporulation killing factor (SKF) is a 26-residue ribosomally assembled and posttranslationally modified sactipeptide. It is produced by Bacillus subtilis 168 and plays a key role in its sporulation. Like all sactipeptides, SKF contains a thioether bond, which links the cysteine residue Cys4 with the α-carbon of the methionine residue Met12. In this study we demonstrate that this bond is generated by the two [4Fe-4S] clusters containing radical SAM enzyme SkfB, which is encoded in the skf operon. By mutational analysis of both cluster-binding sites, we were able to postulate a mechanism for thioether generation which is in agreement with that of AlbA. Furthermore, we were able to show that thioether bond formation is specific toward hydrophobic amino acids at the acceptor site. Additionally we demonstrate that generation of the thioether linkage is leader-peptide-dependent, suggesting that this reaction is the first step in SKF maturation.
芽孢形成杀伤因子（SKF）是一种 26 个氨基酸组成的核糖体组装和翻译后修饰的 sactipeptide。它由枯草芽孢杆菌 168 产生，在其芽孢形成中起着关键作用。与所有 sactipeptides 一样，SKF 含有一个硫醚键，将半胱氨酸残基 Cys4 与甲硫氨酸残基 Met12 的α-碳连接起来。在这项研究中，我们证明了这个键是由两个含有自由基 SAM 酶 SkfB 的[4Fe-4S]簇生成的，SkfB 由 skf 操纵子编码。通过对两个簇结合位点的突变分析，我们能够提出一种硫醚生成的机制，该机制与 AlbA 的机制一致。此外，我们能够证明硫醚键的形成对接受体部位的疏水性氨基酸具有特异性。此外，我们还证明硫醚键的形成依赖于前导肽，这表明该反应是 SKF 成熟的第一步。
