Exploring the role of the YopT-like domain of the Pasteurella multocida Fic protein, PfhB2
Pasteurella multocida is the causative agent for several economically important enzootic diseases in livestock including hemorrhagic septicemia, atrophic rhinitis, and fowl cholera. Importantly, this bacterium can be transferred to humans through contact with nasal secretions or bites from infected animals. Few virulence factors have been identified and characterized for their role in P. multocida virulence. The multidomain, filamentous hemagglutinin (FHA)-like protein, PfhB2, is implicated in virulence, but its activity is unknown. The FHA and Fic domains have been shown to provide protective immunity in turkeys and to adenylylate Rho GTPases in vitro, respectively. In contrast, the YopT-like domain of PfhB2 has not been examined. Here, we show that the PfhB2 YopT domain does not display cysteine protease activity against mammalian Rho GTPases in vitro, unlike its close homolog from Yersinia. Instead, PfhB2 YopT behaves more like its homolog from Histophilus somni, IbpA, and does not induce cytotoxicity of mammalian cells. Further, PfhB2 YopT does not display protease activity against a general protease substrate, FITC-labeled casein. Thus, the activity of PfhB2 YopT is likely toward a specific substrate, possibly of bacterial origin. It remains to be determined whether PfhB2 YopT functions in its own autoproteolysis, similar to what has been reported for another YopT family homolog, AvrPphB from Pseudomonas syringae.
Mattoo, Purdue University.
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