VanS is an integral membrane protein, and a receptor histidine kinase representing on half of the VanSR two component system. In the presence of vancomycin, as well as certain other antibiotics, VanS undergoes autophosphorylation at a conserved histidine residue and then transfers this phosphoryl group to a conserved aspartate on VanR. The phosphorylated form of VanR binds to the promoter region of the vanHAX operon, inducing expression of these genes, which confer glycopeptide antibiotic resistance to the cell. Although the vancomycin resistance mechanism is mostly well-characterised, questions surrounding the structure and mode of activation of VanS remain unanswered. This thesis describes work towards the structural and ligand-binding characterisation of the extracellular \sensor" domain of VanS. Little is known of the structure of this domain, and while there exists evidence in the literature to support numerous theories surrounding the identity of the VanS ligand, no report has yet been made of a direct observation of a binding event involving any VanS protein and its ligand To identify the ligand to VanS, the catalytically active, full-length VanS proteins of Enterococcus faecium (VanSA) and Streptomyces coelicolor (VanSSC) were heterologously expressed, solubilised and purified and binding studies were carried out by solution-state NMR. We present evidence of interactions between vancomycin and both VanS proteins, indicating that direct binding of vancomycin may be the mechanism by which both proteins are activated. The VanSSC extracellular domain was isolated as a synthetic peptide, its structure characterised, and the binding interface between this domain and vancomycin was investigated. Evidence of binding at the N-terminal end of the extracellular domain, in agreement with the findings of Koteva et al. (2010), is presented here. An interaction between vancomycin and DPC detergent micelles was also observed and characterised, and the biological significance of such an interaction is discussed.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:742257 |
| Date | January 2017 |
| Creators | Lockey, Christine |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/102648/ |
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