YscD is an essential component of the plasmid pCD1-encoded type III secretion system (T3SS) of Yersinia pestis. YscD has a single transmembrane (TM) domain that connects a small N-terminal cytoplasmic region (residues 1 to 121) to a larger periplasmic region (residues 143 to 419). Deletion analyses demonstrated that both the N-terminal cytoplasmic region and the C-terminal periplasmic region are essential for YscD function. Additional studies demonstrated that a predicted cytoplasmic forkhead-associated (FHA) domain of YscD is also required for function; in contrast, a predicted periplasmic phospholipid binding (BON) domain and a putative periplasmic "ring-building" domain of YscD could be deleted with no significant effect on the T3S process. Although deletion of the putative "ring-building" domain did not disrupt T3S activity per se, the calcium-dependent regulation of the T3S apparatus was affected. The extreme C-terminal region of YscD (residues 354 to 419) was essential for secretion activity and had a strong dominant negative effect on the T3S process when exported to the periplasm of the wild type parent strain. Finally, replacement of the YscD TM domain with a TM domain of dissimilar sequence had no effect on the T3S process, indicating that the TM domain has no sequence-specific function in the assembly or function of the T3SS.
| Identifer | oai:union.ndltd.org:UMIAMI/oai:scholarlyrepository.miami.edu:oa_dissertations-1434 |
| Date | 23 June 2010 |
| Creators | Ross, Julia A. |
| Publisher | Scholarly Repository |
| Source Sets | University of Miami |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Open Access Dissertations |
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