Autotransporters represent a large superfamily of known and putative virulence factors produced by Gram-negative bacteria. They consist of an N-terminal “passenger domain” responsible for the specific effector functions of the molecule and a C-terminal “β domain” responsible for translocation of the passenger across the bacterial outer membrane. The serine protease autotransporters of Enterobacteriaceae (SPATEs) represent those autotransporters produced by Enterobacteriaceae where, as the name suggests, the passenger domain functions as a serine protease. Members of this family of autotransporters include among others the extracellular serine protease EspP produced by enterohemorrhagic Escherichia coli (EHEC) O157:H7.
EHEC, especially those of serotype O157:H7, have been implicated as causative agents of hemorrhagic colitis and hemolytic-uremic syndrome, both of which include disruption of the normal processes in human blood responsible for maintaining good health. EspP has previously been shown to cleave human coagulation factors V and VIII and has been hypothesized to possibly contribute to the mucosal hemorrhage in patients infected with EHEC.
This thesis aims to better understand the functional significance of EspP in EHEC pathogenesis by analyzing the crystallographic structure of the mature passenger domain of EspP and by investigating, in vitro, its effects on the coagulation and fibrinolytic processes in human blood.
Like the previously determined autotransporter passenger domains, the EspP passenger domain is found to contain an extended right-handed parallel β-helix preceded by an N-terminal globular domain housing the catalytic function of the protease. Of note, however, is the absence of a second globular domain protruding from this β-helix. Furthermore, EspP is found to alter hemostasis in vitro by drastically decreasing the activities of human blood coagulation factors V, VII, VIII and XII, by enhancing platelet-fibrin clot formation, and by accelerating fibrinolysis. These results provide compelling evidence for a pathogenic role played by EspP during EHEC infection.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OTU.1807/43772 |
| Date | 14 January 2014 |
| Creators | Khan, Shekeb |
| Contributors | Pai, Emil F. |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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