Identification and Interrogation of the Herbicidin Biosynthetic Gene Cluster: First Insight into the Biosynthesis of a Rare Undecose Nucleoside Antibiotic

Abstract

Herbicidins are adenosine-based nucleoside antibiotics with an unusual tricyclic undecose core decorated with a (5-hydroxy)tiglyl moiety. Feeding studies are herein reported demonstrating that the tricyclic core is derived from d-glucose and d-ribose, whereas the tiglyl moiety is derived from an intermediate of l-isoleucine catabolism. Identification of the gene cluster for herbicidin A biosynthesis in Streptomyces sp. L-9-10 as well as its verification by heterologous expression in a non-producing host are described, and the results of in vitro characterization of a carboxyl methyltransferase encoded in the cluster, Her8, are presented. Based on these observations, a biosynthetic pathway is proposed for herbicidins.

Elucidation of the Herbicidin Tailoring Pathway Offers Insights into Its Structural Diversity

“…L-9-10 and the initial characterization of the biosynthetic pathway for HBC A ( 1 ). 14 Further investigation of the assembly of the tricyclic undecose core may reveal new mechanisms for C–C bond formation, 15 and elucidation of the peripheral modifications is crucial for diversification of HBCs through pathway engineering. Herein, two BGCs for HBCs ( hbc ) and ANM ( anm ) were identified from Streptomyces sp.…”

“…HbcF/G/H and the HbcH homologue Her9 were each overexpressed in Escherichia coli and purified as N-His 6 -tagged proteins (Figures S68 and S82). The Her8/10 proteins were obtained as previously described, 14 but an attempt to obtain soluble HbcI was unsuccessful. The methylation activity of HbcF and Her8 was tested using 6 , and conversion to 8 was observed in both cases (Figure 3 , i and ii, Figure S69 for a different HPLC method, and Figure S86).…”

Exploring novel herbicidin analogues by transcriptional regulator overexpression and MS/MS molecular networking

“…1:0.7 for 2 and 2:3 for 3 , Additional file 1: Figures S5, S6). This phenomenon arose from the equilibrium between hemiketal and free carbonyl forms of herbicidins, which had also been observed for 11′- O -demethylherbicidin A and 11′- O -demythylherbicidin B in D 2 O according to the literature [13]. To be convenient for comparison, the solvent was switched to DMSO- d 6 for compound 1 .…”

“…During the preparation of this manuscript, the herbicidin biosynthetic gene clusters in S. sp. L-9-10 [13] and S. sp. KIB-027 [12] were reported in succession (Fig.…”

“…Here we report the successful mapping and identification of a herbicidin biosynthetic gene cluster ( hcd ) in S. mobaraensis US-43 by bioinformatics analysis, which is largely homologous to recently reported her in S. sp. L-9-10 [13] and hbc in S. sp. KIB-027 [12] responsible for herbicidin biosynthesis.…”