Polymer Partitioning and Ion Selectivity Suggest Asymmetrical Shape for the Membrane Pore Formed by Epsilon Toxin
Polymer Partitioning and Ion Selectivity Suggest Asymmetrical Shape for the Membrane Pore Formed by Epsilon Toxin
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DOI：
10.1016/j.bpj.2010.05.014
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发表时间：
2010-08-04
影响因子：
3.4
通讯作者：
Bezrukov, Sergey M.
中科院分区：
文献类型：
--
作者：
Nestorovich, Ekaterina M.;Karginov, Vladimir A.;Bezrukov, Sergey M.
使用不同分子量的聚乙二醇，我们探测由厌氧细菌产气荚膜梭菌分泌的肉毒毒素在平面脂质双层中形成的通道。我们发现，孔隙是高度不对称的。从顺式侧（毒素添加侧）通过孔开口进入孔的聚合物的截止尺寸类似于500 Da，而从反式侧进入的聚合物的截止尺寸类似于2300 Da。将这些特征分子量与先前报道的OmpF孔蛋白和α-溶血素通道的特征分子量进行比较，我们估计顺式和反式开口的半径分别为0.4 nm和1.0 nm。与这些发现相对应的最简单的几何形状是截锥。孔的不对称性也证实了在相反方向的盐梯度的反转电位的测量。当孔的反侧的盐浓度较高时，通道的中等阴离子选择性更有效地被盐析。
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.