This item is under embargo and not available online per the author's request. For access information, please visit http://libanswers.wustl.edu/faq/5640.

ORCID

http://orcid.org/https://orcid.org/0000-0001-5305-2080

Date of Award

Winter 1-15-2021

Author's School

Graduate School of Arts and Sciences

Author's Department

Chemistry

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

With the amount of antibiotic resistant infections increasing and the number of new antibiotics entering the pharmaceutical pipeline decreasing, the need to develop new antibiotic is imperative. Utilizing bacteria’s biosynthetic pathways for antimicrobial secondary metabolite production, would allow for unique, complex, and stereoselective compounds to be tested for novel mechanisms of action. The work described herein utilizes a β-lactone forming nonribosomal peptide synthetase (NRPS) to form a library of analogs of the nonribosomal peptide (NRP) natural product, obafluorin. β-lactones are very reactive electrophiles that can form covalent bonds with a wide range of biological targets that may provide alternative mechanisms of action against highly resistant bacterial strains. Within this work, the crystal structure of the NRPS module obiF1 from Burkholderia diffusa is described along with functional studies utilizing the enzymes to investigate the substrate selectivity of the adenylation domain (A). Using combined enzyme assays of obiHDF from Pseudomonas fluorescens, a large library of different analogs probes the promiscuous nature of the transaldolase (obiH) and the NRPS enzymes (obiD and obiF). Among the diverse microbes that produce obafluorin, we were able to swap the NRPS domains and found ubiquitous interactions between the AAr and TAr domains. An organic synthetic route was optimized to yield obafluorin and its analogs in higher yields than can be isolated from culture. This work illuminates the usefulness of NRPS chemoenzymatic synthesis and domain swapping in order to make many possible strained-ring antibiotics.

Language

English (en)

Chair and Committee

Timothy A. Wencewicz

Committee Members

John-Stephen Taylor, Kevin D. Moeller, Joseph M. Jez, Meredith Jackrel,

Available for download on Saturday, January 10, 2026

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