Department of Physics, Institute of Biosciences, Humanities and Exact Sciences, São Paulo State University (UNESP), São José do Rio Preto, SP 15054-000, Brazil.
Department of Physics, North Dakota State University, Fargo, ND 58108-6050, USA.
Biomolecules. 2019 Jul 25;9(8):303. doi: 10.3390/biom9080303.
It is well known that the formation and spatial correlation of lipid domains in the two apposed leaflets of a bilayer are influenced by weak lipid-lipid interactions across the bilayer's midplane. Transmembrane proteins span through both leaflets and thus offer an alternative domain coupling mechanism. Using a mean-field approximation of a simple bilayer-type lattice model, with two two-dimensional lattices stacked one on top of the other, we explore the role of this "structural" inter-leaflet coupling for the ability of a lipid membrane to phase separate and form spatially correlated domains. We present calculated phase diagrams for various effective lipid-lipid and lipid-protein interaction strengths in membranes that contain a binary lipid mixture in each leaflet plus a small amount of added transmembrane proteins. The influence of the transmembrane nature of the proteins is assessed by a comparison with "peripheral" proteins, which result from the separation of one single integral protein into two independent units that are no longer structurally connected across the bilayer. We demonstrate that the ability of membrane-spanning proteins to facilitate domain formation requires sufficiently strong lipid-protein interactions. Weak lipid-protein interactions generally tend to inhibit phase separation in a similar manner for transmembrane as for peripheral proteins.
众所周知，双层膜中两个相邻叶层之间的脂质域的形成和空间相关性受到跨双层中间平面的弱脂质-脂质相互作用的影响。跨膜蛋白贯穿两个叶层，因此提供了另一种域耦合机制。我们使用简单双层型晶格模型的平均场近似，其中两个二维晶格一个堆叠在另一个之上，来探索这种“结构”叶间耦合对脂质膜分相和形成空间相关域的能力的作用。我们为含有双层中每个叶层中的二元脂质混合物以及少量添加的跨膜蛋白的膜呈现了各种有效脂质-脂质和脂质-蛋白相互作用强度的计算相图。通过与“外围”蛋白的比较来评估蛋白质跨膜性质的影响，“外围”蛋白是由一个单一的完整蛋白质分离成两个不再在双层中结构连接的独立单元而产生的。我们证明了跨膜蛋白促进域形成的能力需要足够强的脂质-蛋白相互作用。弱的脂质-蛋白相互作用通常倾向于以类似于跨膜蛋白和外围蛋白的方式抑制相分离。
