Journal
EMBO JOURNAL
Volume 23, Issue 16, Pages 3206-3215Publisher
WILEY
DOI: 10.1038/sj.emboj.7600350
Keywords
AFM; perfringolysin; pore; toxin
Categories
Funding
- NIAID NIH HHS [AI37657, R01 AI037657] Funding Source: Medline
- NIBIB NIH HHS [EB002017, R01 EB002017] Funding Source: Medline
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Perfringolysin O (PFO) is a prototype of the large family of pore-forming cholesterol-dependent cytolysins (CDCs). A central enigma of the cytolytic mechanism of the CDCs is that their membrane-spanning beta-hairpins (the transmembrane amphipathic beta-hairpins (TMHs)) appear to be similar to40 Angstrom too far above the membrane surface to cross the bilayer and form the pore. We now present evidence, using atomic force microscopy (AFM), of a significant difference in the height by which the prepore and pore protrude from the membrane surface: 113+/-5 Angstrom for the prepore but only 73+/-5 Angstrom for the pore. Time-lapse AFM micrographs show this change in height in real time. Moreover, the monomers in both complexes exhibit nearly identical surface features and these results in combination with those of spectrofluorimetric analyses indicate that the monomers remain in a perpendicular orientation to the bilayer plane during this transition. Therefore, the PFO undergoes a vertical collapse that brings its TMHs to the membrane surface so that they can extend across the bilayer to form the beta-barrel pore.
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