Microcystins, cyclic nonribosomal heptapeptides, are the most well-known cyanobacterial toxins. They are exceptionally well studied, but open questions remain concerning their physiological role for the producing microorganism or their suitability as lead compounds for anticancer drug development. One means to study specialized metabolites in more detail is the introduction of functional groups that make a compound amenable for bioorthogonal, so-called click reactions. Although it was reported that microcystins cannot be derivatized by precursor-directed biosynthesis, we successfully used this approach to prepare clickable microcystins. Supplementing different azide- or terminal alkyne containing amino acid analogues into the cultivation medium of microcystin-producing cyanobacteria strains, we found that these strains differ strongly in their substrate acceptance. Exploiting this flexibility, we generated more than 40 different clickable microcystins. We conjugated one of these derivatives with a fluorogenic dye and showed that neither incorporation of the unnatural amino acid analogue nor attachment of the fluorescent label significantly affects the cytotoxicity against cell lines expressing the human organic anion transporting polypeptides 1B1 or 1B3. Using time-lapse microscopy, we observed that the fluorescent microcystin is rapidly taken up into eukaryotic cells expressing these transporters.

中文翻译：

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可点击微囊藻毒素的前体定向生物合成和荧光标记。

微囊藻毒素，环状非核糖体七肽，是最著名的蓝藻毒素。它们得到了非常深入的研究，但关于它们对生产微生物的生理作用或其作为抗癌药物开发的先导化合物的适用性仍然存在悬而未决的问题。更详细地研究特定代谢物的一种方法是引入官能团，使化合物适合生物正交，即所谓的点击反应。尽管据报道不能通过前体定向生物合成衍生出微囊藻毒素，但我们成功地使用这种方法制备了可点击的微囊藻毒素。在产微囊藻毒素蓝藻菌株的培养基中添加不同的含叠氮化物或末端炔烃的氨基酸类似物，我们发现这些菌株在其底物接受度方面差异很大。利用这种灵活性，我们生成了 40 多种不同的可点击微囊藻毒素。我们将这些衍生物中的一种与荧光染料结合，并表明非天然氨基酸类似物的掺入和荧光标记的附着都不会显着影响对表达人类有机阴离子转运多肽 1B1 或 1B3 的细胞系的细胞毒性。使用延时显微镜，我们观察到荧光微囊藻毒素被迅速吸收到表达这些转运蛋白的真核细胞中。我们将这些衍生物中的一种与荧光染料结合，并表明非天然氨基酸类似物的掺入和荧光标记的附着都不会显着影响对表达人类有机阴离子转运多肽 1B1 或 1B3 的细胞系的细胞毒性。使用延时显微镜，我们观察到荧光微囊藻毒素被迅速吸收到表达这些转运蛋白的真核细胞中。我们将这些衍生物中的一种与荧光染料结合，并表明非天然氨基酸类似物的掺入和荧光标记的附着都不会显着影响对表达人类有机阴离子转运多肽 1B1 或 1B3 的细胞系的细胞毒性。使用延时显微镜，我们观察到荧光微囊藻毒素被迅速吸收到表达这些转运蛋白的真核细胞中。