Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherbeg, Germany.
Chem Phys Lipids. 2012 Feb;165(2):216-24. doi: 10.1016/j.chemphyslip.2011.12.012. Epub 2011 Dec 27.
A detailed understanding of biomembrane architecture is still a challenging task. Many in vitro studies have shown lipid domains but much less information is known about the lateral organization of membrane proteins because their hydrophobic nature limits the use of many experimental methods. We examined lipid domain formation in biomimetic Escherichia coli membranes composed of phosphatidylethanolamine and phosphatidylglycerol in the absence and presence of 1% and 5% (mol/mol) membrane multidrug resistance protein, EmrE. Monolayer isotherms demonstrated protein insertion into the lipid monolayer. Subsequently, Brewster angle microscopy was applied to image domains in lipid matrices and lipid-protein mixtures. The images showed a concentration dependent impact of the protein on lipid domain size and shape and more interestingly distinct coexisting protein clusters. Whereas lipid domains varied in size (14-47μm), protein clusters exhibited a narrow size distribution (2.6-4.8μm) suggesting a non-random process of cluster formation. A 3-D display clearly indicates that these proteins clusters protrude from the membrane plane. These data demonstrate distinct co-existing lipid domains and membrane protein clusters as the monofilm is being compressed and illustrate the significant mutual impact of lipid-protein interactions on lateral membrane architecture.
深入了解生物膜结构仍然是一项具有挑战性的任务。许多体外研究表明存在脂质域，但关于膜蛋白的侧向组织的信息却知之甚少，因为其疏水性限制了许多实验方法的应用。我们研究了由磷脂酰乙醇胺和磷脂酰甘油组成的仿生大肠杆菌膜中脂质域的形成，该膜在不存在和存在 1%和 5%（摩尔/摩尔）膜多药耐药蛋白 EmrE 的情况下。单层等温线表明蛋白质插入脂质单层。随后，应用布鲁斯特角显微镜对脂质基质和脂质-蛋白质混合物中的域进行成像。这些图像显示了蛋白质对脂质域大小和形状的浓度依赖性影响，更有趣的是，存在不同的共存蛋白质簇。虽然脂质域的大小（14-47μm）不同，但蛋白质簇的分布范围较窄（2.6-4.8μm），表明簇形成是非随机过程。3D 显示清楚地表明这些蛋白质簇从膜平面突出。这些数据表明，在单分子层被压缩时存在明显的共存脂质域和膜蛋白簇，并说明了脂质-蛋白质相互作用对侧向膜结构的显著相互影响。
