Watasemycin biosynthesis in Streptomyces venezuelae: thiazoline C-methylation by a type B radical-SAM methylase homologue
Watasemycin biosynthesis in Streptomyces venezuelae: thiazoline C-methylation by a type B radical-SAM methylase homologue
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DOI：
10.1039/c6sc03533g
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发表时间：
2017-04-01
期刊：
影响因子：
8.4
通讯作者：
Challis, Gregory L.
中科院分区：
文献类型：
--
作者：
Inahashi, Yuki;Zhou, Shanshan;Challis, Gregory L.
2-羟基苯基噻唑啉是铁螯合非核糖体肽家族的天然产物，在各种革兰氏阴性细菌中起着赋予毒力的铁载体的作用。它们也被报道为革兰氏阳性链霉菌的代谢物。对委内瑞拉链霉菌ATCC 10712的转录分析显示，其基因组含有一个假定的2-羟基苯基噻唑啉生物合成基因簇。该基因簇在coelicolor Streptomyces M1152中的异源表达表明，2-羟基苯基噻唑啉对映opochelin的单甲基和二甲基化衍生物thiazostatin和watasemycin分别是其代谢产物。此外，含有c -甲基化噻唑烷的pyochelin的一种新型异构体isoyochelin被确定为该簇的第三种代谢产物。同时还检测到与绿嘌呤和出版物A/B对应的代谢物。通过与合成标准物的比较，确定了异紫chelin的结构和立体化学性质。本文研究了假单胞菌蛋白中催化噻唑啉还原的PchK同源基因簇中两个基因的作用。其中一种是集群所有代谢产物的生产所必需的，而另一种似乎不参与其中任何一种的生物合成。在编码B型自由基- sam甲基化酶同源物的基因簇中，缺失一个基因会破坏沃他霉素的产生，但不会破坏噻唑他汀或异虫chelin的产生。将噻唑他汀喂给缺乏功能性PchK同源基因的突变体，导致突变体完全转化为沃他霉素，这表明B型自由基- sam甲基化酶的c -甲基化是沃他霉素生物合成的最后一步。
2-Hydroxyphenylthiazolines are a family of iron-chelating nonribosomal peptide natural products that function as virulence-conferring siderophores in various Gram-negative bacteria. They have also been reported as metabolites of Gram-positive Streptomyces species. Transcriptional analyses of Streptomyces venezuelae ATCC 10712 revealed that its genome contains a putative 2-hydroxyphenylthiazoline biosynthetic gene cluster. Heterologous expression of the gene cluster in Streptomyces coelicolor M1152 showed that the mono-and dimethylated derivatives, thiazostatin and watasemycin, respectively, of the 2-hydroxyphenylthiazoline enantiopyochelin are two of its metabolic products. In addition, isopyochelin, a novel isomer of pyochelin containing a C-methylated thiazolidine, was identified as a third metabolic product of the cluster. Metabolites with molecular formulae corresponding to aerugine and pulicatins A/B were also detected. The structure and stereochemistry of isopyochelin were confirmed by comparison with synthetic standards. The role of two genes in the cluster encoding homologues of PchK, which is proposed to catalyse thiazoline reduction in the biosynthesis of enantiopyochelin in Pseudomonas protegens, was investigated. One was required for the production of all the metabolic products of the cluster, whereas the other appears not to be involved in the biosynthesis of any of them. Deletion of a gene in the cluster encoding a type B radical-SAM methylase homologue abolished the production of watasemycin, but not thiazostatin or isopyochelin. Feeding of thiazostatin to the mutant lacking the functional PchK homologue resulted in complete conversion to watasemycin, demonstrating that thiazoline C-methylation by the type B radical-SAM methylase homologue is the final step in watasemycin biosynthesis.