Biochemical basis for the regulation of biosynthesis of antiparasitics by bacterial hormones.

Iti Kapoor,Satish K Nair,Philip Olivares

doi:10.7554/elife.57824

Abstract

Diffusible small molecule microbial hormones drastically alter the expression profiles of antibiotics and other drugs in actinobacteria. For example, avenolide (a butenolide) regulates the production of avermectin, derivatives of which are used in the treatment of river blindness and other parasitic diseases. Butenolides and γ-butyrolactones control the production of pharmaceutically important secondary metabolites by binding to TetR family transcriptional repressors. Here, we describe a concise, 22-step synthetic strategy for the production of avenolide. We present crystal structures of the butenolide receptor AvaR1 in isolation and in complex with avenolide, as well as those of AvaR1 bound to an oligonucleotide derived from its operator. Biochemical studies guided by the co-crystal structures enable the identification of 90 new actinobacteria that may be regulated by butenolides, two of which are experimentally verified. These studies provide a foundation for understanding the regulation of microbial secondary metabolite production, which may be exploited for the discovery and production of novel medicines.

Highlights

The rise of drug-resistant pathogens continues to compromise human health and is exacerbated by the decline in the discovery rate for new anti-infectives.[1,2] A major limitation is the lack of tools that enable access to the vast library of bacterial natural product antibiotics
A retro-synthetic strategy was pursued to allow for the production of avenolide from the convergent synthesis of three key fragments consisting of the iodide 11, the aldehyde 12 and epoxy 10 (Figure 1C) following the reported protocol by Uchida et al.[20]
The discovery of the regulation of secondary metabolite biosynthesis by γ-butyrolactones pushed efforts to use these molecules as ex vivo effectors to induce otherwise silent biosynthetic gene clusters but with little success

Summary

Introduction

The rise of drug-resistant pathogens continues to compromise human health and is exacerbated by the decline in the discovery rate for new anti-infectives.[1,2] A major limitation is the lack of tools that enable access to the vast library of bacterial natural product antibiotics. Despite the fact that statistical surveys depict the number of antibiotics that are genetically encoded within the Streptomyces genus to be in excess of ~300,000 new molecules, a large repertoire of these compounds cannot be produced when the strain is grown under standard laboratory conditions.[3,4]. The responsible biosynthetic genes are ‘silent’ under laboratory condition and are regulated via unknown mechanisms.[5,6]. The diffusible small molecule γ-butyrolactone (GBL) A-factor plays an essential role in the biosynthesis of the antibiotic streptomycin in Streptomyces gresius.

Methods

Results

Conclusion