Journal of natural products

1520-60258362020Jun26Journal of natural productsJ Nat ProdPrecursor-Directed Biosynthesis and Fluorescence Labeling of Clickable Microcystins.196019701960-197010.1021/acs.jnatprod.0c00251Microcystins, 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.MoschnyJuliaJDepartment of Pharmaceutical Biology/Pharmacognosy, Institute of Pharmacy, University of Halle-Wittenberg, 06120 Halle (Saale), Germany.Interfaculty Institute of Microbiology and Infection Medicine, Eberhard Karls University Tübingen, 72076 Tübingen, Germany.LorenzenWolframWCyano Biotech GmbH, 12489 Berlin, Germany.HilferAlexandraACyano Biotech GmbH, 12489 Berlin, Germany.EckenstalerRobertRDepartment of Clinical Pharmacy and Pharmacotherapy, Institute of Pharmacy, Martin-Luther-University Halle-Wittenberg, 06120 Halle (Saale), Germany.JahnsStefanSCyano Biotech GmbH, 12489 Berlin, Germany.EnkeHeikeHCyano Biotech GmbH, 12489 Berlin, Germany.EnkeDanDCyano Biotech GmbH, 12489 Berlin, Germany.SchneiderPhilippPInterfaculty Institute of Microbiology and Infection Medicine, Eberhard Karls University Tübingen, 72076 Tübingen, Germany.BenndorfRalf ARADepartment of Clinical Pharmacy and Pharmacotherapy, Institute of Pharmacy, Martin-Luther-University Halle-Wittenberg, 06120 Halle (Saale), Germany.NiedermeyerTimo H JTHJ0000-0003-1779-7899Department of Pharmaceutical Biology/Pharmacognosy, Institute of Pharmacy, University of Halle-Wittenberg, 06120 Halle (Saale), Germany.Interfaculty Institute of Microbiology and Infection Medicine, Eberhard Karls University Tübingen, 72076 Tübingen, Germany.engJournal ArticleResearch Support, Non-U.S. Gov't20200528