Bacterial type IV secretion systems (T4SSs) can function to export or import DNA, and can deliver effector proteins into a wide range of target cells. Relatively little is known about the structural organization of T4SSs that secrete effector proteins. In this thesis, I describe the isolation and analysis of a membrane-spanning core complex from the <i>Helicobacter pylori cag </i>T4SS, which has an important role in the pathogenesis of gastric cancer. This complex contains five <i>H. pylori </i>proteins, CagM, CagT, Cag3, CagX, and CagY, each of which is required for cag T4SS activity. CagX and CagY are orthologous to the VirB9 and VirB10 components of T4SSs in other bacterial species, and the other three Cag proteins are unique to<i> H. pylori</i>. Negative stain single-particle electron microscopy revealed complexes 41 nm in diameter, characterized by a 19-nm-diameter central ring linked to an outer ring by spoke-like linkers. Incomplete complexes formed by<i> Îcag3 or ÎcagT</i> mutants retained the 19-nm-diameter ring but lack an organized outer ring. Immunogold labeling studies confirmed that Cag3 is a peripheral component of the complex. The <i>cag</i> T4SS core complex has an overall diameter and structural organization that differ considerably from the corresponding features of conjugative T4SSs. These results highlight specialized features of the <i>H. pylori cag</i> T4SS that are optimized for function in the human gastric mucosal environment.
| Identifer | oai:union.ndltd.org:VANDERBILT/oai:VANDERBILTETD:etd-03242017-091315 |
| Date | 30 March 2017 |
| Creators | Frick-Cheng, Arwen Elise |
| Contributors | Mark Denison, Borden Lacy, Melanie Ohi, Eric Skaar, Timothy Cover |
| Publisher | VANDERBILT |
| Source Sets | Vanderbilt University Theses |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.vanderbilt.edu/available/etd-03242017-091315/ |
| Rights | restricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Vanderbilt University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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