Biosynthesis and mode of action of the β-lactone antibiotic obafluorin

Scott, Thomas (2017) Biosynthesis and mode of action of the β-lactone antibiotic obafluorin. Doctoral thesis, University of East Anglia.

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DNA sequencing technologies have advanced rapidly in the 21st century and there are now an abundance of microbial genomes available to mine in search of novel biosynthetic gene clusters and the bioactive natural products they encode. Whilst an enormously exciting prospect, this abundance of genomic data presents a challenge in determining how to select clusters for further study.
To address this issue, this project focusses on the biosynthesis of the β-lactone antibiotic obafluorin produced by the soil bacterium Pseudomonas fluorescens. β-Lactones occur infrequently in nature but possess a variety of potent and valuable biological activities. They are commonly derived from β-hydroxy-α-amino acids, which are themselves privileged chiral building blocks in a variety of pharmacologically and agriculturally important natural products and medicines.
I report the delineation of the entire obafluorin biosynthetic pathway using complementary mutagenesis and biochemical assay-based approaches. As part of this work I have been able to characterise ObaG, a novel PLP-dependent L-threonine transaldolase responsible for the biosynthesis of an unusual nonproteinogenic β-hydroxy-α-amino acid precursor from which the β-lactone ring of obafluorin is derived. Phylogenetic analysis has shed light on the evolutionary origin of this rare enzyme family and has identified further gene clusters encoding putative L-threonine transaldolases. Furthermore, I have been able to biochemically assay an entire intact nonribosomal peptide synthetase that displays a noncanonical domain architecture and is responsible for obafluorin assembly and β-lactone ring formation.
These studies allowed both mechanism- and redundancy-guided genome mining strategies to be developed that might allow the specific targeting of novel chemistry in the uncharted reaches of the natural product world.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Jackie Webb
Date Deposited: 18 May 2018 12:30
Last Modified: 28 Feb 2021 01:38


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