Pentaketide Ansamycin Microansamycins A-I from Micromonospora sp. Reveal Diverse Post-PKS Modifications

Area of Science:

• Natural Product Chemistry
• Molecular Biology
• Microbiology

Background:

• Ansamycins are a class of complex natural products with significant biological activities.
• The biosynthesis of many ansamycins remains poorly understood, particularly those derived from cryptic gene clusters.
• Identifying novel ansamycin biosynthetic pathways is crucial for discovering new therapeutic agents.

Purpose of the Study:

• To elucidate the biosynthetic pathway of novel pentaketide ansamycins.
• To identify the gene cluster responsible for ansamycin production.
• To explore the diversity of post-polyketide synthase (PKS) modifications in ansamycin biosynthesis.

Main Methods:

• Activation of a cryptic gene cluster (mas) through overexpression of a positive regulator gene (mas13).
• Isolation and structural elucidation of nine novel compounds using spectroscopic techniques.
• Bioinformatic analysis to identify genes within the cluster and their putative functions.

Main Results:

• Overexpression of mas13 successfully activated the cryptic mas gene cluster.
• Nine novel pentaketide ansamycins, designated microansamycins A-I, were isolated and characterized.
• The study identified the first described biosynthetic gene cluster for pentaketide ansamycins.
• Diverse and unprecedented post-PKS modifications were observed in the biosynthesis of these ansamycins.

Conclusions:

• The findings reveal a novel biosynthetic gene cluster for pentaketide ansamycins.
• This study provides insights into the diverse enzymatic machinery involved in ansamycin post-PKS tailoring.
• The discovery of microansamycins opens avenues for exploring new bioactive natural products.