Probing the structure-activity relationship of enacyloxins Daniel Van 1 , Lona M. Alkhalaf 1 , Neil J. Oldham 2 , Phillip J. Stansfeld 1 , Gregory L. Challis 1,3 1 University of Warwick, UK, 2 University of Nottingham,UK, 3 Monash University, Australia Acinetobacter baumannii has recently been identified as one of the three multi-drug resistant “critical priority” pathogens by the World Health Organisation, for which new antibiotics are urgently required to treat infections. Most clinically used antibiotics are derived from natural products produced by bacteria and fungi. Enacyloxin IIa is a polyketide antibiotic produced by an unusual polyketide synthase (PKS) system in Burkholderia ambifaria that is highly active against A. baumannii , including antibiotic-resistant clinical isolates. Enacyloxin IIa binds to elongation factor thermo unstable (EF-Tu), preventing its release from the ribosome and inhibiting translation, making it a promising candidate for pre-clinical development. Multiple biosynthetic engineering strategies, including feeding of dihydroxycyclohexane carboxylic acid (DHCCA) analogues to strains blocked in DHCCA biosynthesis and deletion of genes encoding tailoring enzymes, have led to the production of almost 40 novel enacyloxin analogues. An interdisciplinary approach to create further analogues is being pursued to enable a more complete picture of the structure-activity relationship for EF-Tu inhibition to be built. We aim to further diversify the molecule through manipulation of the PKS genes and the introduction of chemical handles for selective derivatisation (e.g., using ‘click’ chemistry). We are also utilising molecular dynamic simulations, native protein mass spectrometry and carbene foot printing to probe binding of enacyloxin IIa and analogues to EF-Tu. Producing more stable and soluble enacyloxin analogues will enable their therapeutic potential for treatment of infections caused by multi- drug resistant A. baumannii to be more extensively assessed.
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© The Author(s), 2022
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