The Aspergillus nidulans enzyme TdiB catalyzes prenyltransfer to the precursor of bioactive asterriquinones

The asterriquinones represent a class of ascomycete metabolic products whose significance stems from remarkable and useful pharmacological activities, among those antiretroviral (e.g., against the HI-virus), antitumor, and antidiabetes properties. Recently, the first genetic locus for an asterriquinone, the clustered terrequinone genes tdiA–E, was identified during a genome-wide screen in Aspergillus nidulans for “orphan” natural product biosynthesis loci. Here, we describe overexpression and characterization of TdiB, which catalyzes the reverse prenylation event during terrequinone A biosynthesis, which is the transfer of dimethylallyl diphosphate to carbon atom 2′ of the intermediate didemethylasterriquinone D, to yield asterriquinone C-1. TdiB does not depend on the presence of divalent metal cations for catalysis and lacks the canonical prenyl diphosphate binding motif (D/N)DXXD.