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Title: Characterisation of putative type VI secretion system effector proteins from Burkholderia cenocepacia
Author: Jones, Richard A.
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2012
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The type VI secretion system (T6SS) is a recently discovered protein secretion mechanism present in many pathogenic Gram-negative bacteria, including the opportunistic pathogen Burkholderia cenocepacia. B. cenocepacia infections occur in patients with cystic fibrosis and chronic granulomatous disease. Such infections can be very serious, and even fatal. The T6SS contains 13 core protein subunits, some of which are proposed to assemble into a protein structure analogous to an inverted bacteriophage T4 contractile tail. This complex has been shown to inject bacterial effector proteins directly into host cells, as well as into the extracellular medium. Three potential effector proteins of the T6SS are TssI, TagA and TagD. These putative effectors are present in B. cenocepacia, and two of them feature C-terminal extensions that are homologous to phospholipase A1 enzymes (TssI BCAS0667 and TagD BCAL1294). Both TssI and TagD, and their PLA1-like C-terminal domains were overproduced in E. coli and their ability to hydrolyse fatty acyl esters was confirmed by enzymatic assays. The PLA1-like domain of the putative TssI effector (BCAS0667) was further characterised and the kinetics determined; it was confirmed to be a psychrophilic phospholipase A1 that utilises a catalytic serine-aspartate-histidine triad. Interactions between the putative effector proteins and other components of the T6SS were investigated using the bacterial adenylate cyclase two-hybrid system (BACTH). This analysis provided evidence to support the idea that different TssI subunits could associate to form heterooligomeric complexes. Interactions of the putative effector proteins TagA and TagD with the core T6SS proteins have also been investigated.
Supervisor: Thomas, Mark Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available