期刊
BIOPHYSICAL JOURNAL
卷 99, 期 3, 页码 782-789出版社
CELL PRESS
DOI: 10.1016/j.bpj.2010.05.014
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资金
- National Institutes of Health [2R44AI074105-02]
- Eunice Kennedy Shriver National Institute of Child Health and Human Development
- National Institutes of Health
- National Institute of Allergy and Infectious Diseases (NIAID)
Using poly-(ethylene glycol)s of different molecular weights, we probe the channels formed in planar lipid bilayers by epsilon toxin secreted by the anaerobic bacterium Clostridium perfringens. We find that the pore is highly asymmetric. The cutoff size of polymers entering the pore through its opening from the cis side, the side of toxin addition, is similar to 500 Da, whereas the cutoff size for the polymers entering from the trans side is similar to 2300 Da. Comparing these characteristic molecular weights with those reported earlier for OmpF porin and the alpha-Hemolysin channel, we estimate the radii of cis and trans openings as 0.4 nm and 1.0 nm, respectively. The simplest geometry corresponding to these findings is that of a truncated cone. The asymmetry of the pore is also confirmed by measurements of the reversal potential at oppositely directed salt gradients. The moderate anionic selectivity of the channel is salted-out more efficiently when the salt concentration is higher at the trans side of the pore.
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