Characterization of the Tautomycin Biosynthetic Gene Cluster from Streptomyces spiroverticillatus Unveiling New Insights into Dialkylmaleic Anhydride and Polyketide Biosynthesis

Abstract

Tautomycin (TTM) is a highly potent and specific protein phosphatase inhibitor isolated from Streptomyces spiroverticillatus. The biological activity of TTM makes it an important lead for drug discovery, whereas its spiroketal-containing polyketide chain and rare dialkylmaleic anhydride moiety draw attention to novel biosynthetic chemistries responsible for its production. To elucidate the biosynthetic machinery associated with these novel molecular features, the ttm biosynthetic gene cluster from S. spiroverticillatus was isolated and characterized, and its involvement in TTM biosynthesis was confirmed by gene inactivation and complementation experiments. The ttm cluster was localized to a 86-kb DNA region, consisting of 20 open reading frames that encode three modular type I polyketide synthases (TtmHIJ), one type II thioesterase (TtmT), five proteins for methoxymalonyl-S-acyl carrier protein biosynthesis (Ttm-ABCDE), eight proteins for dialkylmaleic anhydride biosynthesis and regulation (TtmKLMNOPRS), as well as two additional regulatory proteins (TtmF and TtmQ) and one tailoring enzyme (TtmG). A model for TTM biosynthesis is proposed based on functional assignments from sequence analysis, which agrees well with previous feeding experiments, and has been further supported by in vivo gene inactivation experiments. These findings set the stage to fully investigate TTM biosynthesis and to biosynthetically engineer new TTM analogs.

Hygrobafilomycin, a cytotoxic and antifungal macrolide bearing a unique monoalkylmaleic anhydride moiety, from Streptomyces varsoviensis

“…24 As for the alkylmaleic anhydride substituent, one may deduce a biosynthetic scheme from the tautomycin pathway. 25 Osada and colleagues 25 suggested that the dialkylmaleic anhydride moiety is biosynthesized through an aldol condensation of methylmalonylCoA and a-ketoglutarate derived from the Krebs cycle. In analogy, a plausible route toward the monoalkylmaleic anhydride side chain of 6 would involve an aldol condensation of acetyl-CoA with the C-5 unit derived from a-keto glutarate, followed by dehydration.…”

Characterization of the Biosynthesis Gene Cluster for the Pyrrole Polyether Antibiotic Calcimycin (A23187) in Streptomyces chartreusis NRRL 3882

“…Spiroketal rings are found in tautomycin, avermectins, and spirandienes (10,14,18). It have been postulated that the spiroketal ring formation could proceed spontaneously by dual nucleophilic attack on the carbonyl carbon atom (C-14) by the two hydroxyl groups at C-10 and C-18 (Fig.…”

Spirotoamides A and B, novel 6,6-spiroacetal polyketides isolated from a microbial metabolite fraction library

“…The carbon skeleton of spirotoamides A(1) and B(2) is likely assembled by a type I polyketide synthase, which might catalyze the loading of the acetate unit and the condensation of four malonylCoAs, four methylmalonyl-CoAs and one ethylmalonyl-CoA. Based on the knowledge of tautomycin 20 and avermectin 21 biosyntheses, the presence of a dihydroxyl ketone precursor was expected in the formation of the spiroacetal structure (Figure 4). We recently analyzed the biosynthesis of reveromycin A and identified RevJ responsible for the stereospecific spiroacetal formation from the dihydroxyl ketone precursor.…”