Duclohier Hervé, Alder Glenn, Kociolek Karol, Leplawy Miroslaw T
UMR 6026 CNRS-Université de Rennes I, Bâtiment 13, Campus de Beaulieu, 35042 Rennes, France.
J Pept Sci. 2003 Nov-Dec;9(11-12):776-83. doi: 10.1002/psc.523.
The multiple conductance levels displayed by the antibiotic alamethicin in planar lipid bilayers is explained by a dynamic 'barrel-stave' model, the conducting pore resulting from the aggregation of up to ten helical amphipathic helical monomers. However, the precise assignment of an oligomerization state to a particular single-channel conductance substate is far from being experimentally clear. In addition, it could be useful to tailor a given channel geometry to selectively allow the permeation of solutes with different molecular sizes, whilst retaining a high voltage-dependence. To control the aggregation state of the channel, the TASP (template assembled synthetic proteins) strategy was applied to synthesize structurally defined oligomers, i.e. dimer, trimer, tetramer. The modulation of conductance properties of three alamethicin tetramers with the length and flexibility of the linkers of the 'open' or linear template is described. It is shown that the introduction of an alanine between the contiguous lysines to which are tethered C-terminally modified alamethicin helical monomers stabilizes the open channel states, whereas the alanine substitution by Pro-Gly, a reverse beta-turn promoting motif, increases voltage-dependence and leads to single-channel conductance values more in line with the expected ones from a tetrameric bundle.
抗生素短杆菌肽A在平面脂质双分子层中显示出的多重电导水平，可用动态的“桶板”模型来解释，导电孔是由多达十个螺旋两亲性螺旋单体聚集而成。然而，将寡聚化状态精确地对应到特定的单通道电导亚状态，在实验上还远不清楚。此外，定制特定的通道几何结构，以选择性地允许不同分子大小的溶质渗透，同时保持高电压依赖性，可能会很有用。为了控制通道的聚集状态，采用了模板组装合成蛋白（TASP）策略来合成结构明确的寡聚体，即二聚体、三聚体、四聚体。本文描述了利用“开放”或线性模板的连接子的长度和灵活性，对三种短杆菌肽A四聚体的电导特性进行调制。结果表明，在C末端修饰的短杆菌肽A螺旋单体所连接的相邻赖氨酸之间引入丙氨酸，可稳定开放通道状态，而用脯氨酸-甘氨酸（一种促进反向β-转角的基序）取代丙氨酸，则会增加电压依赖性，并导致单通道电导值更符合四聚体束的预期值。
