Biochemical and genetic basis of oligocyclic aromatic polyketide formation in basidiomycetes
Final Report Abstract
Using Webcap Mushrooms (genus Cortinarius in the wider, traditional sense) as a model, this project investigated how mushroom-forming basidiomycetes assemble the scaffold structure of certain chromophoric, yet toxic natural products, the oligocyclic polyketides. An evolutionarily distinct and hitherto uncharacterized class of polyketide synthases, i.e., biosynthesis enzymes, was characterized based on two representatives (CoPKS1 und CoPKS4). These two enzymes of Cortinarius odorifer share virtually identical amino acid sequences, yet differ in their product profiles: by heterologous production in the host organism Aspergillus niger and subsequent chromatographic analysis it was shown that CoPKS1 nearexclusively produces the octaketide atrochrysone carboxylic acid while CoPKS4 produces both this compound and the heptaketide 6-hydroxymusizin. Either enzyme shows a proline-rich sequence that is unique for polyketide synthases. Yet, this sequence differs between CoPKS1 and CoPKS4. By production and heterologous expression of hybrid genes, it was shown that proline-rich sequence is essential for enzymatic activity but does not impact the product spectrum. However, further hybrid enzymes demonstrate that it is the ketosynthase domain that determines the product spectrum. By modelling this domain in silico, a plausible amino acid position was not obvious which could have determined chain length. All members of this class of polyketide synthase share another unique feature in that they lack an N-terminal starter unit acyltransferase domain, the SAT domain. However, this domain is integral to other basidiomycete polyketide synthases, the orsellinic acid synthases (OASs). These are enzymes that catalyze the formation of monocyclic polyketides. Through genetic engineering, the SAT domain was removed from three representatives of the OASs. However, the catalytic activity was retained. Due to the lack or the dispensibility of the SAT domain, the enzymes characterized in this project represent the most compact polyketide synthases, both to produce mono- and oligocyclic compounds, which may make them versatile catalysts for future biotechnological applications. As CoPKS1/CopPKS4-type polyketide synthases occur in numerous other basidiomycetes outside the genus Cortinarius, the results of this project are universally applicable and help predict oligocyclic polyketides in members of other genera.
Publications
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Mind the mushroom: natural product biosynthetic genes and enzymes of Basidiomycota. Natural Product Reports, 38(4), 702-722.
Gressler, Markus; Löhr, Nikolai A.; Schäfer, Tim; Lawrinowitz, Stefanie; Seibold, Paula Sophie & Hoffmeister, Dirk
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Genetic and Biochemical Basis of Oligocyclic Aromatic Polyketide Formation in Mushrooms. 31st Fungal Genetics Conference at Asilomar, Pacific Grove, CA. March 15 - March 20, 2022
Löhr N. A.; Gressler M.; Motter J.; Müller M. & Hoffmeister D.
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The Ketosynthase Domain Controls Chain Length in Mushroom Oligocyclic Polyketide Synthases. ChemBioChem, 24(3).
Löhr, Nikolai A.; Urban, Maximilian C.; Eisen, Frederic; Platz, Lukas; Hüttel, Wolfgang; Gressler, Markus; Müller, Michael & Hoffmeister, Dirk
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Unprecedented Mushroom Polyketide Synthases Produce the Universal Anthraquinone Precursor. Angewandte Chemie International Edition, 61(24).
Löhr, Nikolai A.; Eisen, Frederic; Thiele, Wiebke; Platz, Lukas; Motter, Jonas; Hüttel, Wolfgang; Gressler, Markus; Müller, Michael & Hoffmeister, Dirk
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Basidiomycete non-reducing polyketide synthases function independently of SAT domains. Fungal Biology and Biotechnology, 10(1).
Löhr, Nikolai A.; Rakhmanov, Malik; Wurlitzer, Jacob M.; Lackner, Gerald; Gressler, Markus & Hoffmeister, Dirk
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Do unspecific peroxygenases dream of selectivity? 35. Irseer Naturstofftage, Irsee, Germany, April 26 – April 28, 2023.
Platz L.; Löhr N. A.; Eisen F.; Girkens P.; Braun K.; Hüttel W.; Hoffmeister D. & Müller M.
