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Target specificity of tac toxins in salmonella

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Title: Target specificity of tac toxins in salmonella
Authors: Hall, Alexander
Item Type: Thesis or dissertation
Abstract: Toxin-antitoxin (TA) systems are cellular regulators that are implicated in mediating the bacterial response to stress. The pathogen Salmonella Typhimurium carries multiple chromosomal TA systems, including three type II TA systems belonging to the recently described TacAT family that encode GNAT domain acetyltransferase toxins – TacAT1, TacAT2 and TacAT3. It has been shown that TacT1 inhibits cell proliferation through the N-acetylation of aminoacyl-tRNA which results in disruption of protein synthesis. This thesis addresses the target specificity of Tac toxins. In working toward this, I contributed to the characterisation of the TacT2 and TacT3 toxins, confirming that they also acetylate aminoacyl-tRNAs and intoxicate the cell though the inhibition of translation. Furthermore, I have developed a new mass spectrometry methodology for the identification of aminoacyl-tRNAs targeted by Tac toxins and have shown the exquisite specificity of each of these toxins toward glycyl-tRNAGly in vivo. This thesis reports the attempts to structurally characterise the TacT-tRNA complex, including implementation of in vitro tRNA synthesis and aminoacylation for crystallographic study. I also present the experimentally determined structure of ItaT, a Tac family homolog from E. coli, and the identification of the substrate specificity of this toxin confirming the primary target as isoleucyl-tRNAIle. A comparison of the solved structures of GNAT domain acetyltransferase toxins and their defined target specificities sheds light on some of the important structural features that contribute to tRNA target recognition.
Content Version: Open Access
Issue Date: Sep-2019
Date Awarded: Jan-2020
URI: http://hdl.handle.net/10044/1/95299
DOI: https://doi.org/10.25560/95299
Copyright Statement: Creative Commons Attribution NonCommercial Licence
Supervisor: Helaine, Sophie
Holden, David
Sponsor/Funder: Medical Research Council
Funder's Grant Number: MR/J006874/1
Department: Department of Medicine
Publisher: Imperial College London
Qualification Level: Doctoral
Qualification Name: Doctor of Philosophy (PhD)
Appears in Collections:Medicine PhD theses



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