Date of Award


Degree Type


Degree Name

Master of Science


Microbiology and Immunology


Dr. Carole Creuzenet

Second Advisor

Dr. John McCormick

Third Advisor

Dr. Susan Koval


HcpE (HP0235) is a cysteine-rich protein that is specific to and highly conserved in Helicobacters. HcpE elicits strong antibody production in patients infected with H. pylori. We demonstrated that HcpE is secreted by H. pylori. Structural modeling demonstrated that HcpE is a solenoid protein that requires the formation of many disulphide bonds prior to secretion. Moreover, the presence of Sell-like repeat (SLR) motifs implies that protein-protein interactions are necessary for function of HcpE. Two experimental approaches were implemented to identify interacting partners for HcpE. Using mature folded HcpE, an interaction with HPOl 84, a protein of unknown function was identified. Using unfolded HcpE, a specific folding factor, DsbG was identified. The interaction with DsbG was confirmed biochemically. DsbG not only interacts with unfolded HcpE, but this interaction could solubilize unfolded HcpE probably via disulfide bond formation between the many cysteines of HcpE. A tissue culture model using gastric cells and an hcpE knockout mutant was used to investigate the role of HcpE during infection. Difficulties with viability and differential expression of surface carbohydrates by the hcpE mutant, which altered its surface properties, complicated the analysis. Identifying interactions with host cells and with other H. pylori proteins will contribute to our understanding of the biological role of HcpE in H. pylori pathogenesis.



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