Biosynthetic code for divergolide assembly in a bacterial mangrove endophyte

Area of Science:

• Microbial natural product biosynthesis
• Synthetic biology
• Medicinal chemistry

Background:

• Divergolides are structurally diverse ansamycins produced by Streptomyces sp. endophytes of the mangrove Bruguiera gymnorrhiza.
• Understanding their biosynthesis is key to unlocking novel chemical scaffolds.

Purpose of the Study:

• To elucidate the biosynthetic pathway of divergolides.
• To identify the genes responsible for the production of these ansamycins.
• To revise the biosynthetic model based on new findings.

Main Methods:

• Genomic analysis of the Streptomyces sp. endophyte.
• Identification and characterization of the divergolide gene cluster (div).
• Detailed polyketide synthase (PKS) domain analysis.
• Isolation and full structural elucidation of four new divergolide congeners.

Main Results:

• A gene locus (div gene cluster) for divergolide biosynthesis was identified.
• The cluster encodes biosynthesis of 3-amino-5-hydroxybenzoate and rare extender units (ethylmalonyl-CoA, isobutylmalonyl-CoA).
• Polyketide assembly involves a modular type I PKS and tailoring enzymes like a Baeyer-Villiger oxygenase.
• A revised model shows formation of four ansansamycin chromophore types from one precursor.

Conclusions:

• The div gene cluster provides a comprehensive blueprint for divergolide ansamycin biosynthesis.
• Detailed PKS analysis confirms stereochemical integrity and offers insights into chromophore formation.
• The study presents a revised model for the formation of diverse ansamycin chromophores from a single polyketide precursor.