<p> Bacterial cell division is an essential process, which is initiated by forming the Z-ring as a cytoskeletal scaffold at the midcell site, followed by the recruitment of a series of divisome proteins. In <i>Escherichia coli</i> (Ec), at least 15 divisome proteins (FtsZ, FtsA, ZipA, FtsK, FtsQ, FtsB, FtsL, FtsI, FtsW, FtsN, FtsE, FtsX, ZapA, AmiC, EnvC) have been implicated in this process. The components of the cell division machinery proteins in <i>Neisseria gonorrhoeae</i> (Ng) differs from <i>E. coli. N. gonorrhoeae</i> possesses FtsA, but lacks FtsB. ZipA and FtsL in <i>N. gonorrhoeae</i> have low identity to ZipA and FtsL from <i>E. coli</i>. Our laboratory has studied the central division protein FtsZ in <i>N. gonorrhoeae</i>. Thus, my research investigated the role of <i>N. gonorrhoeae</i> FtsA in cell division and investigated the interactions between divisome proteins from <i>N. gonorrhoeae</i> to understand divisome assembly.</p>
<p>This study determined the association of FtsA<sub>Ng</sub> with FtsZ</sub>Ng and other divisome proteins in <i>N. gonorrhoeae</i> and identified the functional domains of FtsA<sun>Ng</sub> involved in these interactions using a bacterial two-hybrid (B2H) assay. FtsA<sub>Ng</sub> interacted with FtsZ<sub>Ng</sub>, FtsK<sub>Ng</sub>, FtsW<sub>Ng</sub>, FtsQ<sub>Ng</sub>, and FtsN<sub>Ng</sub>. Self-interactions of FtsA<sub>Ng</sub> and FtsZ<sub>Ng</sub> were also detected. FtsI<sub>Ng</sub>, FtsE<sub>Ng</sub> and FtsX<sub>Ng</sub> did not interact with FtsA<sub>Ng</sub>. The 2A<sub>1</sub>, 2A<sub>2</sub> and 2B domains of FtsA<sub>Ng</sub> were sufficient to interact with FtsZ<sub>Ng</sub> independently. Domain 2A<sub>1</sub> interacted with FtsK<sub>Ng</sub> and FtsN<sub>Ng</sub>. Domain 2B of FtsA<sub>Ng</sub> interacted with FtsK<sub>Ng</sub>, FtsQ<sub>Ng</sub>, and FtsN<sub>Ng</sub>. Domain 2A<sub>2</sub> of FtsA<sub>Ng</sub> interacted with FtsQ<sub>Ng</sub>, FtsW<sub>Ng</sub>, and FtsN<sub>Ng</sub>. These data suggest that FtsA in <i>N. gonorrhoeae</i> plays a key role in interactions with FtsZ and other divisome proteins.</p>
<p>The potential interactions between divisome proteins in <i>N. gonorrhoeae</i> were examined using B2H assays. The comparisons between the <i>N. gonorrhoeae</i> divisome protein interaction network and those of <i>E. coli</i> and <i>S. pneumoniae</i> indicates that the divisome protein interactome of <i>N. gonorrhoeae</i> is more similar to that of <i>S. pneumoniae</i> and differs from that of <i>E. coli</i>. The comparisons revealed that compared to the interactions in <i>E. coli</i> and <i>S. pneumoniae</i>, more interactions between divisome proteins upstream of FtsA<sub>Ng</sub> (including FtsA<sub>Ng</sub>) and downstream of FtsA<sub>Ng</sub> were observed in <i>N. gonorrhoeae</i> while fewer interactions between divisome proteins downstream of FtsA<sub>Ng</sub> were observed in <i>N. gonorrhoeae</i>. Possible reasons for this include the inability of ZipA<sub>Ng</sub> to interact with other divisome proteins and the absence of FtsL and FtsB in <i>N. gonorrhoeae</i>, resulting in the lack of an FtsQ-FtsB-FtsL complex in <i>N. gonorrhoeae</i>. These results indicate a possibly different divisome assembly in <i>N. gonorrhoeae</i> from that proposed models for <i>E. coli</i>.</p>
A model for FtsA<sub>Ng</sub> structure was predicted based on structural homology modeling with the resolved crystal structure of <i>Thermotoga maritima</i> FtsA. Four domains on the molecule were identified, designated 1A, 1C, 2B and 2A (including 2A<sub>1</sub> and 2A<sub>2</sub>). Domains 2A and 2B of FtsA were highly conserved based on multi-sequence alignments of FtsAs from 30 bacteria. FtsA<sub>Ng</sub> located to the division site in <i>N. gonorrhoeae</i> cells and the ratio of FtsA to FtsZ ranged from 1:24 to 1: 33 in three <i>N. gonorrhoeae</i> strains, which gave a lower cellular concentration of FtsA compared to other organisms.</p>
<p>I also determined that overexpression of FtsA<sub>Ng</sub> in <i>E. coli</i> led to cell filamentous in rod-shaped <i>E. coli</i> and cell enlargement and aggregation in mutant, round <i>E. coli</i>. FtsA<sub>Ng</sub> failed to complement an <i>ftsA</i><sub>Ec</sub>-deletion <i>E. coli</i> strain although the overexperssion of FtsA<sub>Ng</sub> disrupted <i>E. coli</i> cell division. In addition, overexpression of FtsA<sub>Ng</sub> only affected cell division in some cells and its localization in <i>E. coli</i> was independent of interaction with <i>E. coli</i> FtsA or FtsZ. These results indicate that FtsA<sub>Ng</sub> exhibits a species-specific functionality and <i>E. coli</i> is not a suitable model for studying FtsA<sub>Ng</sub> functionality.</p>
<p>This is the first study to characterize FtsA from <i>N. gonorrhoeae</i> in cell division. I identified novel functional domains of FtsA<sub>Ng</sub> involved in interactions with other divisome proteins. The <i>N. gonorrhoeae</i> divisome protein interaction network determined by B2H assays provides insight into divisome assembly in <i>N. gonorrhoeae</i></p>.
Identifer | oai:union.ndltd.org:USASK/oai:usask.ca:etd-05052011-113213 |
Date | 09 May 2011 |
Creators | Li, Yan |
Contributors | Dillon, Jo-Anne R., Todd, Chris, Wang, Hong, Howard, Peter, Wilson, Ken, Shafer, William M. |
Publisher | University of Saskatchewan |
Source Sets | University of Saskatchewan Library |
Language | English |
Detected Language | English |
Type | text |
Format | application/pdf |
Source | http://library.usask.ca/theses/available/etd-05052011-113213/ |
Rights | unrestricted, 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 University of Saskatchewan 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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