Markin V S, Martinac B
Institute of Electrochemistry, Moscow, USSR.
Biophys J. 1991 Nov;60(5):1120-7. doi: 10.1016/S0006-3495(91)82147-6.
Various amphipathic compounds have been found to activate mechanosensitive (MS) ion channels in the bacterium Escherichia coli. These results were interpreted qualitatively in terms of the bilayer couple hypothesis. Here we present a mathematical model that describes the results quantitatively. According to the model, the uneven partitioning of amphipaths between the monolayers of the cell membrane causes one monolayer to be compressed and the other expanded. Because the open probability (Po) of the E. coli channels increased independently of which monolayer the amphipaths partitioned into, the model suggests that Po of the MS channels is determined by the monolayer having higher tension. We derived a relation between Po and amphipath concentration. The kinetics of Po variation after exposure of the cell membrane to the amphipaths was calculated based on this relation. The results fit satisfactorily the experimental data obtained with the cationic amphipath chlorpromazine and with the anionic amphipath trinitrophenol. Experiments which should further test the predictions following from the model are discussed.
人们发现多种两亲性化合物可激活大肠杆菌中的机械敏感（MS）离子通道。这些结果依据双层偶联假说进行了定性解释。在此，我们提出一个能对结果进行定量描述的数学模型。根据该模型，两亲分子在细胞膜单分子层间的不均匀分布致使一个单分子层被压缩，另一个则膨胀。由于大肠杆菌通道的开放概率（Po）增加与两亲分子分配到哪个单分子层无关，该模型表明MS通道的Po由具有更高张力的单分子层决定。我们推导了Po与两亲分子浓度之间的关系。基于此关系计算了细胞膜暴露于两亲分子后Po变化的动力学。结果与使用阳离子两亲分子氯丙嗪和阴离子两亲分子三硝基苯酚获得的实验数据吻合良好。还讨论了应进一步检验该模型预测结果的实验。
