Investigating the Ligand Interactions Between E. coli PBP1b, Moenomycin-based Compounds, and Beta-Lactam Compounds

Alexander, Peter (2017) Investigating the Ligand Interactions Between E. coli PBP1b, Moenomycin-based Compounds, and Beta-Lactam Compounds. MRes thesis, University of Lincoln.

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Investigating the Ligand Interactions Between E. coli PBP1b, Moenomycin-based Compounds, and Beta-Lactam Compounds
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Abstract

Antimicrobial resistance is a growing problem in this era. Resistance to the majority of clinical
antibiotics (including those of a ‘last line of defence’ nature) has been seen in a number of
laboratory and clinical settings. One method aiming at reducing this problem is altering
existing antimicrobial compounds, in order to improve pharmacological effects (avoiding
resistance mechanisms, improved spectrum of use). Looking at the interactions between the
antimicrobial compounds and their targets can determine whether modifications to current
antimicrobials (such as moenomycin A) have altered the mode of action.
ecoPBP1B is a bifunctional glycosyltransferase that could be used as a model for beta lactams
and moenomycins, aiding in the design and development of novel antimicrobials based on
these families. This project aims to show whether ecoPBP1b can be used as a model for novel
antimicrobials, such as seeing whether novel MoeA analogues with peptides attached (to
facilitate entry into the bacterial cell) still retain their ability to bind to glycosyltransferases.
In addition, this project looked at whether different beta-lactams would significantly alter
the conformation of the transpeptidase domain of ecoPBP1b.
Building on previous studies into ecoPBP1b, we managed to successfully produce usable
quantities of ecoPBP1b for crystallisation in conjunction with a variety of ligands. Crystals
were produced potentially containing complexes including such compounds as AI167-p and
AI168-p (MoeA analogues), cefotaxime, cephradine, and a novel beta-lactamase inhibitor
(CW-019).
3D structures of ecoPBP1b in complex with AI167 were produced, successfully showing the
MoeA analogue bound into the transglycosylase active site. This showed that the addition of
peptides to the moenomycin molecule has not interfered with the interactions required for
the compound to bind to the transglycosylase domain. In addition, ecoPBP1b was cocrystallised with ampicillin bound to the penicillin binding region, matching with previous
studies.
There are issues that need to be addressed with regards to ecoPBP1b before it can be used
as a reliable model, especially with beta-lactams. However, the main project goal (using
ecoPBP1b for novel MoeA analogues) has been achieved, as well as furthering insights into
crystallisation of proteins in general.

Keywords:Antimicrobial resistance, Antimicrobial compounds
Divisions:College of Science
ID Code:37640
Deposited On:04 Oct 2019 14:23

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