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Title: Action of Salmonella invasion proteins : virulence factors that determine entry into mammalian cells
Author: Hayward, R. D.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2000
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This thesis investigates the function of S. typhimurium SipB and SipC, both essential for invasion and delivery. Following expression in laboratory E. coli, purified SipC formed oligomers in solution and bundled actin filaments independently of host cell components, an activity directed by the N-terminal domain, while additionally the C-terminal domain nucleated actin polymerisation at the barbed-ends of actin filaments, both functions only previously described in eukaryotes. The ability of SipC to elicit actin condensation and cytoskeletal rearrangements in vivo was confirmed by microinjection into cultured mammalian cells, although as SipC associated with liposomes it is possible that its activities are normally directed from the host cell membrane. Studies of actin nucleation by the SipC C-terminal domain suggested that it might resemble that underlying the biogenesis of eukaryotic microvilli. SipB localised to the pathogen surface during cell entry. Unusually, purified protein could be maintained in aqueous solution but also integrated into both mammalian cell membranes and phospholipid vesicles, a process that induced a significant conformational change. However, in both states, the protein assembled into hexamers via an N-terminal protease resistant domain predicted to form a trimeric coiled-coil. SipB was non-hemolytic and did not disrupt lipid bilayer integrity, but bound free fatty acids in solution.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available