Interdisciplinary Research Center HALOmem, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, 06120 Halle/Saale, Germany; Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, 06120 Halle/Saale, Germany.
Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, 06120 Halle/Saale, Germany.
Biochim Biophys Acta Biomembr. 2021 Dec 1;1863(12):183725. doi: 10.1016/j.bbamem.2021.183725. Epub 2021 Aug 10.
Certain amphiphilic copolymers form lipid-bilayer nanodiscs from artificial and natural membranes, thereby rendering incorporated membrane proteins optimal for structural analysis. Recent studies have shown that the amphiphilicity of a copolymer strongly determines its solubilization efficiency. This is especially true for highly negatively charged membranes, which experience pronounced Coulombic repulsion with polyanionic polymers. Here, we present a systematic study on the solubilization of artificial multicomponent lipid vesicles that mimic inner mitochondrial membranes, which harbor essential membrane-protein complexes. In particular, we compared the lipid-solubilization efficiencies of established anionic with less densely charged or zwitterionic and even cationic copolymers in low- and high-salt concentrations. The nanodiscs formed under these conditions were characterized by dynamic light scattering and negative-stain electron microscopy, pointing to a bimodal distribution of nanodisc diameters with a considerable fraction of nanodiscs engaging in side-by-side interactions through their polymer rims. Overall, our results show that some recent, zwitterionic copolymers are best suited to solubilize negatively charged membranes at high ionic strengths even at low polymer/lipid ratios.
某些两亲性共聚物可以从人工和天然膜中形成脂质双层纳米盘，从而使所包含的膜蛋白最适合结构分析。最近的研究表明，共聚物的两亲性强烈决定其增溶效率。对于带负电荷的膜来说尤其如此，因为带负电荷的膜与聚阴离子聚合物之间会发生明显的库仑排斥。在这里，我们对模拟线粒体内部膜的人工多组分脂质囊泡的增溶进行了系统研究，线粒体内部膜含有重要的膜蛋白复合物。特别是，我们在低盐和高盐浓度下比较了已建立的阴离子与电荷密度较低或两性离子甚至阳离子共聚物的脂质增溶效率。在这些条件下形成的纳米盘通过动态光散射和负染色电子显微镜进行了表征，表明纳米盘直径呈双峰分布，相当一部分纳米盘通过聚合物边缘进行并排相互作用。总的来说，我们的结果表明，一些最近的两性离子共聚物即使在低聚合物/脂质比例下，在高离子强度下也最适合溶解带负电荷的膜。
