Authentic Heterologous Expression of the Tenellin Iterative Polyketide Synthase Nonribosomal Peptide Synthetase Requires Coexpression with an Enoyl Reductase

Abstract

The tenS gene encoding tenellin synthetase (TENS), a 4239-residue polyketide synthase nonribosomal-peptide synthetase (PKS-NRPS) from Beauveria bassiana, was expressed in Aspergillus oryzae M-2-3. This led to the production of three new compounds, identified as acyl tetramic acids, and numerous minor metabolites. Consideration of the structures of these compounds indicates that the putative C-terminal thiolester reductase (R) domain does not act as a reductase, but appears to act as a Dieckmann cyclase (DKC). Expression of tenS in the absence of a trans-acting ER component encoded by orf3 led to errors in assembly of the polyketide component, giving clues to the mode of programming of highly reducing fungal PKS. Coexpression of tenS with orf3 from the linked gene cluster led to the production of a correctly elaborated polyketide. The NRPS adenylation domain possibly shows the first identified fungal signature sequences for tyrosine selectivity.

Common biosynthetic origins for polycyclic tetramate macrolactams from phylogenetically diverse bacteria

“…These eukaryal hybrid enzymes function iteratively in the PKS portion of the enzyme and noniteratively in the NRPS subunits (24). The fungal enzymes display a catalytic domain arrangement with clear similarity to that of FtdB (Fig.…”

Regulatory cascade and biological activity of Beauveria bassiana oosporein that limits bacterial growth after host death

“…In contrast, genetic analyses of the biosynthetic pathway of the 2-pyridone tenellin revealed that this compound does not appear to contribute to B. bassiana virulence (40,41). This system also has been exploited for novel compound discovery, with expression of the tenellin nonribosomal peptide synthase in Aspergillus oryzae leading to the production of several new compounds and the use of chemical epigenetic modifiers in B. bassiana altering the selectivity of tenellin polyketide synthase to produce different products (42,43).…”

An Iterative Module in the Azalomycin F Polyketide Synthase Contains a Switchable Enoylreductase Domain

“…Selective processing during two successive iterations of polyketide chain extension is a known feature in highly reducing fully iterative polyketide synthases 29, 30, 31. In the LovB PKS, for example, which synthesizes the nonaketide core of the cholesterol‐lowering compound lovastatin using a single PKS module, an integral methyltransferase domain selectively methylates the β‐ketothioester formed after three rounds of chain extension 29.…”