The major outer membrane protein (MOMP) of <I>Chlamydia</I> shares several biochemical properties with classical porin proteins. To directly test the "porin channel" hypothesis at the molecular level, MOMP was reconstituted into planar lipid bilayers where it gave rise to "triple-barrelled" channels which were modified by an anti-MOMP neutralising monoclonal antibody. These observations are consistent with the well characterised homo-oligomeric nature of MOMP previously revealed by biochemical analysis, and the "triple-barrelled" behaviour of other porins. MOMP channels were weakly anion selective (P<SUB>Cl</SUB>/P<SUB>K</SUB> ~ 2) and permeable to ATP. They may therefore be a route by which <I>Chlamydia</I> can take advantage of host nucleoside triphosphates, and explain why some anti-MOMP antibodies neutralise infection. In order to undertake more detailed studies of the MOMP structure/function relationship, recombinant MOMP from both <I>C. psittaci</I> and <I>C. pneumoniae</I> have been cloned and expressed. The recombinant proteins were functionally reconstituted in planar lipid and analysed at the single channel level. Both form porin-like ion channels that are functionally similar to the native protein. The <I>C. psittaci</I> recombinant porin was modified by the same anti-MOMP neutralising monoclonal antibody that effected the native protein. In contrast to the native protein, both recombinant <I>C. psittaci</I> (P<SUB>Cl</SUB>/<SUB>K</SUB> ~ 0.38) and <I>C. pneumonia </I>(P<SUB>Cl</SUB>/P<SUB>K</SUB> ~ 0.49) proteins were marginally cation selective. This is the first time native function has been demonstrated for recombinant chlamydial MOMP and will have an important impact on the future development of subunit vaccines.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:664069 |
| Date | January 1999 |
| Creators | Wyllie, Susan |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/22762 |
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