title: Genetic, molecular, and biochemical basis of fungal tropolone biosynthesis.
abstract: A gene cluster encoding the biosynthesis of the fungal tropolone stipitatic acid was discovered in Talaromyces stipitatus (Penicillium stipitatum) and investigated by targeted gene knockout. A minimum of three genes are required to form the tropolone nucleus: tropA encodes a nonreducing polyketide synthase which releases 3-methylorcinaldehyde; tropB encodes a FAD-dependent monooxygenase which dearomatizes 3-methylorcinaldehyde via hydroxylation at C-3; and tropC encodes a non-heme Fe(II)-dependent dioxygenase which catalyzes the oxidative ring expansion to the tropolone nucleus via hydroxylation of the 3-methyl group. The tropA gene was characterized by heterologous expression in Aspergillus oryzae, whereas tropB and tropC were successfully expressed in Escherichia coli and the purified TropB and TropC proteins converted 3-methylorcinaldehyde to a tropolone in vitro. Finally, knockout of the tropD gene, encoding a cytochrome P450 monooxygenase, indicated its place as the next gene in the pathway, probably responsible for hydroxylation of the 6-methyl group. Comparison of the T. stipitatus tropolone biosynthetic cluster with other known gene clusters allows clarification of important steps during the biosynthesis of other fungal compounds including the xenovulenes, citrinin, sepedonin, sclerotiorin, and asperfuranone.
authors.affiliation: University of Bristol, School of Chemistry, Cantock's Close, Bristol BS8 1TS, United Kingdom.
authors.forename: Jack
authors.initials: J
authors.lastname: Davison
authors.forename: Ahmed
authors.initials: A
authors.lastname: al Fahad
authors.forename: Menghao
authors.initials: M
authors.lastname: Cai
authors.forename: Zhongshu
authors.initials: Z
authors.lastname: Song
authors.forename: Samar Y
authors.initials: SY
authors.lastname: Yehia
authors.forename: Colin M
authors.initials: CM
authors.lastname: Lazarus
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Bailey
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Simpson
authors.forename: Russell J
authors.initials: RJ
authors.lastname: Cox
mesh_terms: D001203:Ascomycota / Q000235:genetics* / Q000378:metabolism*; D001236:Aspergillus oryzae; D053898:Biosynthetic Pathways / Q000235:genetics / Q000502:physiology*; D002853:Chromatography, Liquid; D019295:Computational Biology; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D049308:Dioxygenases / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli; D055786:Gene Knockout Techniques; D013058:Mass Spectrometry; D005810:Multigene Family / Q000235:genetics* / Q000502:physiology; D010105:Oxygenases / Q000235:genetics / Q000378:metabolism; D048630:Polyketide Synthases / Q000235:genetics / Q000378:metabolism; D014170:Transformation, Genetic; D014334:Tropolone / Q000378:metabolism*
chemical_list: D048630:Polyketide Synthases; D014334:Tropolone; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases; D049308:Dioxygenases; C020066:dimethylaniline monooxygenase (N-oxide forming)