The major outer membrane protein of Chlamydia psittaci functions as a porin-like ion channel.
The major outer membrane protein (MOMP) of Chlamydia species shares several biochemical properties with classical porin proteins. Secondary structure analysis by circular dichroism now reveals that MOMP purified from Chlamydia psittaci has a predominantly beta-sheet content (62%), which is also typical of bacterial porins. Can MOMP form functional ion channels? To directly test the "porin channel" hypothesis at the molecular level, the MOMP was reconstituted into planar lipid bilayers, where it gave rise to multibarreled channels, probably trimers, which were modified by an anti-MOMP monoclonal antibody. These observations are consistent with the well-characterized homo-oligomeric nature of MOMP previously revealed by biochemical analysis and with the triple-barreled behavior of other porins. MOMP channels were weakly anion selective (PCl/PK approximately 2) and permeable to ATP. They may therefore be a route by which Chlamydia can take advantage of host nucleoside triphosphates and explain why some anti-MOMP antibodies neutralize infection. These findings have broad implications on the search for an effective chlamydial vaccine to control the significant human and animal diseases caused by these organisms.
Wyllie
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S
Moredun Research Institute, International Research Centre, Pentland Science Park, Penicuik, Midlothian EH26 0PZ, United Kingdom.
Ashley
R H
RH
Longbottom
D
D
Herring
A J
AJ
D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000502:physiology*; D002463:Cell Membrane Permeability; D002691:Chlamydophila psittaci / Q000502:physiology*; D004229:Dithiothreitol / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D005960:Glucosides; D015151:Immunoblotting; D008051:Lipid Bilayers / Q000378:metabolism; D018272:Porins / Q000737:chemistry / Q000502:physiology*; D017433:Protein Structure, Secondary; D012995:Solubility
D001425:Bacterial Outer Membrane Proteins; D005960:Glucosides; D008051:Lipid Bilayers; D018272:Porins; C069991:outer membrane protein, Chlamydia psittaci 6BC; C018619:octyl-beta-D-glucoside; D004229:Dithiothreitol