Biosynthesis of Dothideomins Reveals a Fungal P450 That Constructs the Tricyclo[5.2.2.0.4,8]undecane-Imbedded Core Skeleton.

Abstract

Dothideomins are antibacterial bis(anthraquinone) polyketides isolated from the endophytic fungus Dothideomycetes sp. BMC-101, featuring a unique 6/6/6/5/6/6/6 heptacyclic scaffold imbedded with a tricyclo[5.2.2.0.^4,8]undecane core. Although the structures and antibacterial potential are attractive, the biosynthesis process and the formation of a heptacyclic scaffold, especially the tricyclo[5.2.2.0.^4,8]undecane cage-like core, are unclear. Here, we elucidated the biosynthesis of dothideomins C and D encoded by a dot gene cluster through heterologous expression, in vivo feeding experiments, and in vitro biochemical assays. Our findings reveal an enzyme cascade involved in the conversion of the precursor emodin into dothideomins. Specifically, the cytochrome P450 monooxygenase DotG is shown to solely catalyze the unprecedented formation of triple C-C bonds and construct the tricyclo[5.2.2.0.^4,8]undecane-embedded skeleton. This study enhances the comprehension of the P450 enzyme-controlled formation of complex natural products.