A salmonella toxin induces persister formation via acetylation of tRNA
File(s)Cheverton-A-2016-PhD-Thesis.pdf (70.77 MB)
Finalised Thesis
Author(s)
Cheverton, Angie
Type
Thesis
Abstract
Persisters have been identified in almost all free-living bacteria and many obligate intracellular pathogens. Bacterial persisters are transiently tolerant to multiple antibiotics and are thought to be responsible for recurrent infections. The formation of non-growing persisters relies on Toxin-Antitoxin (TA) modules. These are ubiquitous molecular switches controlling bacterial growth via the release of a toxin component, which reversibly interferes with an essential cellular process. Salmonella enterica serovar Typhimurium is an intracellular pathogen that forms persisters to high levels upon internalization by macrophages and relies for that on at least 14 TA modules. Of these, 3 constitute a poorly characterized TA family where the toxin contains a predicted GCN5 N- acetyltransferase domain (GNAT). In this work, I have shown that two of the GNAT TA modules, TA6 and TA8, are bona fide TA modules. Both toxins require the predicted Acetyl Coenzyme A domain to function. T8 acetylates the Nα amine group of the amino acid charged to tRNA molecules. This results in N-blocked translationally incompetent aatRNA leading to inhibition of protein synthesis and growth arrest. T8 is a novel acetyltransferase that dimerizes allowing for positive patches on the surface of the dimer to facilitate tRNA binding. Peptidyl tRNA hydrolase (Pth), recognises and hydrolyses T8-acetylated aatRNAs, allowing for the detoxification of cells producing T8 and thereby resumption of growth marking exit from a persister state.
Version
Open Access
Date Issued
2016-04
Date Awarded
2016-08
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Helaine, Sophie
Holden, David
Sponsor
Imperial College London
Medical Research Council (Great Britain)
Grant Number
WMAD_F34175
WMNM_P52347
Publisher Department
Department of Medicine
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)