Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, the Netherlands.
Department of Biophysical Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, the Netherlands.
Nat Commun. 2022 Mar 25;13(1):1605. doi: 10.1038/s41467-022-29272-x.
Cell membranes provide a selective semi-permeable barrier to the passive transport of molecules. This property differs greatly between organisms. While the cytoplasmic membrane of bacterial cells is highly permeable for weak acids and glycerol, yeasts can maintain large concentration gradients. Here we show that such differences can arise from the physical state of the plasma membrane. By combining stopped-flow kinetic measurements with molecular dynamics simulations, we performed a systematic analysis of the permeability of a variety of small molecules through synthetic membranes of different lipid composition to obtain detailed molecular insight into the permeation mechanisms. While membrane thickness is an important parameter for the permeability through fluid membranes, the largest differences occur when the membranes transit from the liquid-disordered to liquid-ordered and/or to gel state, which is in agreement with previous work on passive diffusion of water. By comparing our results with in vivo measurements from yeast, we conclude that the yeast membrane exists in a highly ordered and rigid state, which is comparable to synthetic saturated DPPC-sterol membranes.
细胞膜为分子的被动运输提供了一种具有选择性的半透性屏障。这种性质在不同的生物体之间有很大的差异。虽然细菌细胞质膜对弱酸和甘油具有很高的通透性，但酵母可以维持大的浓度梯度。在这里，我们表明这种差异可能源于质膜的物理状态。通过结合停流动力学测量和分子动力学模拟，我们对各种小分子通过不同脂质组成的合成膜的渗透性进行了系统分析，从而深入了解了渗透机制。虽然膜厚度是通过流体膜渗透的重要参数，但当膜从无序液体状态转变为有序液体状态和/或凝胶状态时，差异最大，这与之前关于水的被动扩散的研究结果一致。通过将我们的结果与酵母体内测量进行比较，我们得出结论，酵母膜处于高度有序和刚性的状态，这与合成的饱和 DPPC-固醇膜相当。
