Structure and function of bacterial proteins secreted by the type three secretion and twin arginine translocation pathways

<p>The Type Three Secretion Systems (T3SSs) of Gram-negative bacteria, including Shigella, Salmonella, and Enteropathogenic/Enterohaemorrhagic Escherichia coli (EPEC/EHEC), pass virulence factors directly into the host to mediate invasion. Prior to secretion down the narrow T3SS channel, effec...

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Main Authors: Lillington, J, James Lillington
Other Authors: Lea, S
Format: Thesis
Language:English
Published: 2011
Subjects:
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author Lillington, J
James Lillington
author2 Lea, S
author_facet Lea, S
Lillington, J
James Lillington
author_sort Lillington, J
collection OXFORD
description <p>The Type Three Secretion Systems (T3SSs) of Gram-negative bacteria, including Shigella, Salmonella, and Enteropathogenic/Enterohaemorrhagic Escherichia coli (EPEC/EHEC), pass virulence factors directly into the host to mediate invasion. Prior to secretion down the narrow T3SS channel, effector proteins associate with chaperone proteins. The binding enables the T3SS to keep effectors soluble and partially unfolded for secretion. In the first part of this thesis, the association of one promiscuous chaperone, Spa15 of Shigella flexneri, with three of its cognate effectors has been studied. In addition to the role this plays in secretion, the binding of one particular substrate leads to Spa15 being involved in the regulation of the T3SS. The oligomerisation and impact of substrate binding upon Spa15 has been determined by crystallography and EPR. Once secreted, T3SS effectors subvert the host cytoskeleton for the benefit of the bacteria. Soluble homologues of Spa15 effectors from EHEC and Salmonella have been purified, and their interactions with host GTPases which lead to stress fibre phenotypes observed.</p> <p>The Twin Arginine Translocation (Tat) pathway provides a contrasting view of bacterial secretion. Instead of preventing folding in the cytoplasm, it is a criterion of transport that the protein be folded. One of the reasons for internal folding is the necessity to insert cofactors which could not be incorporated externally. In the second part of this thesis, a protein which exemplifies this necessity is studied. This is PhoD, the model protein for Tat export from Bacillus subtilis. PhoD is an alkaline phosphodiesterase expressed to scavenge phosphate in times of phosphate deficiency. The structure of PhoD has been solved, and the protein is shown to be able to cleave a component of its own cell wall. It uses an unusual catalytic site more reminiscent of the eukaryotic purple acid phosphatases than of other currently known alkaline phosphatases. Furthermore this site appears to require metal binding before export from the bacterial cytoplasm.</p>
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spelling oxford-uuid:a69f34ac-0edc-4c27-961b-d1638c6d51b32022-03-27T02:48:36ZStructure and function of bacterial proteins secreted by the type three secretion and twin arginine translocation pathwaysThesishttp://purl.org/coar/resource_type/c_db06uuid:a69f34ac-0edc-4c27-961b-d1638c6d51b3Molecular biophysics (biochemistry)CrystallographyBiophysical chemistryProtein chemistryEnglishOxford University Research Archive - Valet2011Lillington, JJames LillingtonLea, STimmel, C<p>The Type Three Secretion Systems (T3SSs) of Gram-negative bacteria, including Shigella, Salmonella, and Enteropathogenic/Enterohaemorrhagic Escherichia coli (EPEC/EHEC), pass virulence factors directly into the host to mediate invasion. Prior to secretion down the narrow T3SS channel, effector proteins associate with chaperone proteins. The binding enables the T3SS to keep effectors soluble and partially unfolded for secretion. In the first part of this thesis, the association of one promiscuous chaperone, Spa15 of Shigella flexneri, with three of its cognate effectors has been studied. In addition to the role this plays in secretion, the binding of one particular substrate leads to Spa15 being involved in the regulation of the T3SS. The oligomerisation and impact of substrate binding upon Spa15 has been determined by crystallography and EPR. Once secreted, T3SS effectors subvert the host cytoskeleton for the benefit of the bacteria. Soluble homologues of Spa15 effectors from EHEC and Salmonella have been purified, and their interactions with host GTPases which lead to stress fibre phenotypes observed.</p> <p>The Twin Arginine Translocation (Tat) pathway provides a contrasting view of bacterial secretion. Instead of preventing folding in the cytoplasm, it is a criterion of transport that the protein be folded. One of the reasons for internal folding is the necessity to insert cofactors which could not be incorporated externally. In the second part of this thesis, a protein which exemplifies this necessity is studied. This is PhoD, the model protein for Tat export from Bacillus subtilis. PhoD is an alkaline phosphodiesterase expressed to scavenge phosphate in times of phosphate deficiency. The structure of PhoD has been solved, and the protein is shown to be able to cleave a component of its own cell wall. It uses an unusual catalytic site more reminiscent of the eukaryotic purple acid phosphatases than of other currently known alkaline phosphatases. Furthermore this site appears to require metal binding before export from the bacterial cytoplasm.</p>
spellingShingle Molecular biophysics (biochemistry)
Crystallography
Biophysical chemistry
Protein chemistry
Lillington, J
James Lillington
Structure and function of bacterial proteins secreted by the type three secretion and twin arginine translocation pathways
title Structure and function of bacterial proteins secreted by the type three secretion and twin arginine translocation pathways
title_full Structure and function of bacterial proteins secreted by the type three secretion and twin arginine translocation pathways
title_fullStr Structure and function of bacterial proteins secreted by the type three secretion and twin arginine translocation pathways
title_full_unstemmed Structure and function of bacterial proteins secreted by the type three secretion and twin arginine translocation pathways
title_short Structure and function of bacterial proteins secreted by the type three secretion and twin arginine translocation pathways
title_sort structure and function of bacterial proteins secreted by the type three secretion and twin arginine translocation pathways
topic Molecular biophysics (biochemistry)
Crystallography
Biophysical chemistry
Protein chemistry
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