Wilmsen H U, Pattus F, Buckley J T
European Molecular Biology Laboratory, Heidelberg, Federal Republic of Germany.
J Membr Biol. 1990 Apr;115(1):71-81. doi: 10.1007/BF01869107.
The cytolytic toxin aerolysin was found to form ion channels which displayed slight anion selectivity in planar lipid bilayers. In voltage-clamp experiments the ion current flowing through the channels was homogeneous indicating a defined conformation and a uniform size. The channels remained open between -70 to +70 mV, but outside this range they underwent voltage-dependent inactivation which was observed as open-closed fluctuations at the single-channel level. Zinc ions not only prevented the formation of channels by inhibiting oligomerization of monomeric aerolysin but they also induced a closure of preformed channels in a voltage-dependent fashion. The results of a Hill plot indicated that 2-3 zinc ions bound to a site within the channel lumen. Proaerolysin, and a mutant of aerolysin in which histidine 132 was replaced by an asparagine, were both unable to oligomerize and neither could form channels. This is evidence that oligomerization is a necessary step in channel formation.
细胞溶解毒素气单胞菌溶素被发现可形成离子通道，这些通道在平面脂质双分子层中表现出轻微的阴离子选择性。在电压钳实验中，流经通道的离子电流是均匀的，这表明其具有确定的构象和统一的大小。通道在-70至+70 mV之间保持开放，但在此范围之外，它们会经历电压依赖性失活，这在单通道水平上表现为开闭波动。锌离子不仅通过抑制单体气单胞菌溶素的寡聚化来阻止通道的形成，还以电压依赖性方式诱导预先形成的通道关闭。希尔图的结果表明，2至3个锌离子与通道腔内的一个位点结合。原气单胞菌溶素以及气单胞菌溶素中组氨酸132被天冬酰胺取代的突变体，都无法进行寡聚化，也都不能形成通道。这证明寡聚化是通道形成过程中的一个必要步骤。
